Database commands (#5417)

* dabase access commands

* select expression

* select using expressions

* cargo fmt

* alias for database

* database where command

* expression operations

* and and or operators

* limit and sort by commands

crates/nu-command/src/database/commands/and.rs

@@ -0,0 +1,143 @@
+use crate::database::values::dsl::ExprDb;
+
+use super::super::SQLiteDatabase;
+use nu_engine::CallExt;
+use nu_protocol::{
+    ast::Call,
+    engine::{Command, EngineState, Stack},
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span, SyntaxShape,
+    Value,
+};
+use sqlparser::ast::{BinaryOperator, Expr, Query, Select, SetExpr};
+
+#[derive(Clone)]
+pub struct AndDb;
+
+impl Command for AndDb {
+    fn name(&self) -> &str {
+        "db and"
+    }
+
+    fn usage(&self) -> &str {
+        "Includes an AND clause for a query or expression"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build(self.name())
+            .required("where", SyntaxShape::Any, "Where expression on the table")
+            .category(Category::Custom("database".into()))
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["database", "where"]
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "selects a column from a database with a where clause",
+                example: r#"db open db.mysql 
+    | db select a 
+    | db from table_1 
+    | db where ((db col a) > 1) 
+    | db and ((db col b) == 1) 
+    | db describe"#,
+                result: None,
+            },
+            Example {
+                description: "Creates a nested where clause",
+                example: r#"db open db.mysql 
+    | db select a 
+    | db from table_1 
+    | db where ((db col a) > 1 | db and ((db col a) < 10)) 
+    | db describe"#,
+                result: None,
+            },
+        ]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let value: Value = call.req(engine_state, stack, 0)?;
+        let expr = ExprDb::try_from_value(&value)?.into_native();
+
+        let value = input.into_value(call.head);
+        if let Ok(expression) = ExprDb::try_from_value(&value) {
+            let expression = Expr::BinaryOp {
+                left: Box::new(expression.into_native()),
+                op: BinaryOperator::And,
+                right: Box::new(expr),
+            };
+
+            let expression: ExprDb = Expr::Nested(Box::new(expression)).into();
+
+            Ok(expression.into_value(call.head).into_pipeline_data())
+        } else if let Ok(mut db) = SQLiteDatabase::try_from_value(value.clone()) {
+            db.query = match db.query {
+                Some(query) => Some(modify_query(query, expr, call.head)?),
+                None => {
+                    return Err(ShellError::GenericError(
+                        "Connection without query".into(),
+                        "Missing query in the connection".into(),
+                        Some(call.head),
+                        None,
+                        Vec::new(),
+                    ))
+                }
+            };
+
+            Ok(db.into_value(call.head).into_pipeline_data())
+        } else {
+            Err(ShellError::CantConvert(
+                "expression or query".into(),
+                value.get_type().to_string(),
+                value.span()?,
+                None,
+            ))
+        }
+    }
+}
+
+fn modify_query(mut query: Query, expression: Expr, span: Span) -> Result<Query, ShellError> {
+    query.body = match query.body {
+        SetExpr::Select(select) => Ok(SetExpr::Select(modify_select(select, expression, span)?)),
+        _ => Err(ShellError::GenericError(
+            "Query without a select".into(),
+            "Missing a WHERE clause before an AND clause".into(),
+            Some(span),
+            None,
+            Vec::new(),
+        )),
+    }?;
+
+    Ok(query)
+}
+
+fn modify_select(
+    mut select: Box<Select>,
+    expression: Expr,
+    span: Span,
+) -> Result<Box<Select>, ShellError> {
+    let new_expression = match &select.selection {
+        Some(expr) => Ok(Expr::BinaryOp {
+            left: Box::new(expr.clone()),
+            op: BinaryOperator::And,
+            right: Box::new(expression),
+        }),
+        None => Err(ShellError::GenericError(
+            "Query without a select".into(),
+            "Missing a WHERE clause before an AND clause".into(),
+            Some(span),
+            None,
+            Vec::new(),
+        )),
+    }?;
+
+    select.as_mut().selection = Some(new_expression);
+    Ok(select)
+}

crates/nu-command/src/database/commands/from.rs

@@ -74,18 +74,16 @@ fn create_query(table: String) -> Query {
 
 fn modify_query(mut query: Query, table: String) -> Query {
     query.body = match query.body {
-        SetExpr::Select(select) => SetExpr::Select(Box::new(modify_select(select, table))),
+        SetExpr::Select(select) => SetExpr::Select(modify_select(select, table)),
         _ => SetExpr::Select(Box::new(create_select(table))),
     };
 
     query
 }
 
-fn modify_select(select: Box<Select>, table: String) -> Select {
+fn modify_select(mut select: Box<Select>, table: String) -> Box<Select> {
-    Select {
+    select.as_mut().from = create_from(table);
-        from: create_from(table),
+    select
-        ..select.as_ref().clone()
-    }
 }
 
 fn create_select(table: String) -> Select {

crates/nu-command/src/database/commands/limit.rs

@@ -0,0 +1,77 @@
+use super::super::SQLiteDatabase;
+use crate::database::values::dsl::ExprDb;
+use nu_engine::CallExt;
+use nu_protocol::{
+    ast::Call,
+    engine::{Command, EngineState, Stack},
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, SyntaxShape, Value,
+};
+
+#[derive(Clone)]
+pub struct LimitDb;
+
+impl Command for LimitDb {
+    fn name(&self) -> &str {
+        "db limit"
+    }
+
+    fn usage(&self) -> &str {
+        "Limit result from query"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build(self.name())
+            .required(
+                "limit",
+                SyntaxShape::Int,
+                "Number of rows to extract for query",
+            )
+            .category(Category::Custom("database".into()))
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["database", "limit"]
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Limits selection from table",
+            example: r#"db open db.mysql 
+    | db from table_a 
+    | db select a 
+    | db limit 10 
+    | db describe"#,
+            result: None,
+        }]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let limit: Value = call.req(engine_state, stack, 0)?;
+        let expr = ExprDb::try_from_value(&limit)?.into_native();
+
+        let mut db = SQLiteDatabase::try_from_pipeline(input, call.head)?;
+        db.query = match db.query {
+            Some(mut query) => {
+                query.limit = Some(expr);
+                Some(query)
+            }
+            None => {
+                return Err(ShellError::GenericError(
+                    "Connection without query".into(),
+                    "The connection needs a query defined".into(),
+                    Some(call.head),
+                    None,
+                    Vec::new(),
+                ))
+            }
+        };
+
+        Ok(db.into_value(call.head).into_pipeline_data())
+    }
+}

crates/nu-command/src/database/commands/mod.rs

@@ -1,11 +1,16 @@
+mod and;
 mod collect;
 mod command;
 mod describe;
 mod from;
+mod limit;
 mod open;
+mod or;
+mod order_by;
 mod query;
 mod schema;
 mod select;
+mod where_;
 
 // Temporal module to create Query objects
 mod testing;
@@ -13,14 +18,19 @@ use testing::TestingDb;
 
 use nu_protocol::engine::StateWorkingSet;
 
+use and::AndDb;
 use collect::CollectDb;
 use command::Database;
 use describe::DescribeDb;
 use from::FromDb;
+use limit::LimitDb;
 use open::OpenDb;
+use or::OrDb;
+use order_by::OrderByDb;
 use query::QueryDb;
 use schema::SchemaDb;
 use select::ProjectionDb;
+use where_::WhereDb;
 
 pub fn add_commands_decls(working_set: &mut StateWorkingSet) {
     macro_rules! bind_command {
@@ -34,14 +44,19 @@ pub fn add_commands_decls(working_set: &mut StateWorkingSet) {
 
     // Series commands
     bind_command!(
+        AndDb,
         CollectDb,
         Database,
         DescribeDb,
         FromDb,
         QueryDb,
+        LimitDb,
         ProjectionDb,
         OpenDb,
+        OrderByDb,
+        OrDb,
         SchemaDb,
-        TestingDb
+        TestingDb,
+        WhereDb
     );
 }

crates/nu-command/src/database/commands/open.rs

@@ -31,8 +31,8 @@ impl Command for OpenDb {
 
     fn examples(&self) -> Vec<Example> {
         vec![Example {
-            description: "",
+            description: "Open a sqlite file",
-            example: r#"""#,
+            example: r#"db open file.sqlite"#,
             result: None,
         }]
     }

crates/nu-command/src/database/commands/or.rs

@@ -0,0 +1,143 @@
+use crate::database::values::dsl::ExprDb;
+
+use super::super::SQLiteDatabase;
+use nu_engine::CallExt;
+use nu_protocol::{
+    ast::Call,
+    engine::{Command, EngineState, Stack},
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, Span, SyntaxShape,
+    Value,
+};
+use sqlparser::ast::{BinaryOperator, Expr, Query, Select, SetExpr};
+
+#[derive(Clone)]
+pub struct OrDb;
+
+impl Command for OrDb {
+    fn name(&self) -> &str {
+        "db or"
+    }
+
+    fn usage(&self) -> &str {
+        "Includes an OR clause for a query or expression"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build(self.name())
+            .required("where", SyntaxShape::Any, "Where expression on the table")
+            .category(Category::Custom("database".into()))
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["database", "where"]
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "selects a column from a database with a where clause",
+                example: r#"db open db.mysql 
+    | db select a 
+    | db from table_1 
+    | db where ((db col a) > 1) 
+    | db or ((db col b) == 1) 
+    | db describe"#,
+                result: None,
+            },
+            Example {
+                description: "Creates a nested where clause",
+                example: r#"db open db.mysql 
+    | db select a 
+    | db from table_1 
+    | db where ((db col a) > 1 | db or ((db col a) < 10)) 
+    | db describe"#,
+                result: None,
+            },
+        ]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let value: Value = call.req(engine_state, stack, 0)?;
+        let expr = ExprDb::try_from_value(&value)?.into_native();
+
+        let value = input.into_value(call.head);
+        if let Ok(expression) = ExprDb::try_from_value(&value) {
+            let expression = Expr::BinaryOp {
+                left: Box::new(expression.into_native()),
+                op: BinaryOperator::Or,
+                right: Box::new(expr),
+            };
+
+            let expression: ExprDb = Expr::Nested(Box::new(expression)).into();
+
+            Ok(expression.into_value(call.head).into_pipeline_data())
+        } else if let Ok(mut db) = SQLiteDatabase::try_from_value(value.clone()) {
+            db.query = match db.query {
+                Some(query) => Some(modify_query(query, expr, call.head)?),
+                None => {
+                    return Err(ShellError::GenericError(
+                        "Connection without query".into(),
+                        "Missing query in the connection".into(),
+                        Some(call.head),
+                        None,
+                        Vec::new(),
+                    ))
+                }
+            };
+
+            Ok(db.into_value(call.head).into_pipeline_data())
+        } else {
+            Err(ShellError::CantConvert(
+                "expression or query".into(),
+                value.get_type().to_string(),
+                value.span()?,
+                None,
+            ))
+        }
+    }
+}
+
+fn modify_query(mut query: Query, expression: Expr, span: Span) -> Result<Query, ShellError> {
+    query.body = match query.body {
+        SetExpr::Select(select) => Ok(SetExpr::Select(modify_select(select, expression, span)?)),
+        _ => Err(ShellError::GenericError(
+            "Query without a select".into(),
+            "Missing a WHERE clause before an OR clause".into(),
+            Some(span),
+            None,
+            Vec::new(),
+        )),
+    }?;
+
+    Ok(query)
+}
+
+fn modify_select(
+    mut select: Box<Select>,
+    expression: Expr,
+    span: Span,
+) -> Result<Box<Select>, ShellError> {
+    let new_expression = match &select.selection {
+        Some(expr) => Ok(Expr::BinaryOp {
+            left: Box::new(expr.clone()),
+            op: BinaryOperator::Or,
+            right: Box::new(expression),
+        }),
+        None => Err(ShellError::GenericError(
+            "Query without a select".into(),
+            "Missing a WHERE clause before an OR clause".into(),
+            Some(span),
+            None,
+            Vec::new(),
+        )),
+    }?;
+
+    select.as_mut().selection = Some(new_expression);
+    Ok(select)
+}

crates/nu-command/src/database/commands/order_by.rs

@@ -0,0 +1,97 @@
+use crate::database::values::dsl::ExprDb;
+
+use super::super::SQLiteDatabase;
+use nu_engine::CallExt;
+use nu_protocol::{
+    ast::Call,
+    engine::{Command, EngineState, Stack},
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, SyntaxShape, Value,
+};
+use sqlparser::ast::OrderByExpr;
+
+#[derive(Clone)]
+pub struct OrderByDb;
+
+impl Command for OrderByDb {
+    fn name(&self) -> &str {
+        "db order-by"
+    }
+
+    fn usage(&self) -> &str {
+        "Orders by query"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build(self.name())
+            .switch("ascending", "Order by ascending values", Some('a'))
+            .switch("nulls_first", "Show nulls first in order", Some('n'))
+            .rest(
+                "select",
+                SyntaxShape::Any,
+                "Select expression(s) on the table",
+            )
+            .category(Category::Custom("database".into()))
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["database", "select"]
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "orders query by a column",
+            example: r#"db open db.mysql 
+    | db from table_a 
+    | db select a 
+    | db order-by a 
+    | db describe"#,
+            result: None,
+        }]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let asc = call.has_flag("ascending");
+        let nulls_first = call.has_flag("nulls_first");
+
+        let vals: Vec<Value> = call.rest(engine_state, stack, 0)?;
+        let value = Value::List {
+            vals,
+            span: call.head,
+        };
+        let expressions = ExprDb::extract_exprs(value)?;
+
+        let mut db = SQLiteDatabase::try_from_pipeline(input, call.head)?;
+        db.query = match db.query {
+            Some(mut query) => {
+                let mut order_expr: Vec<OrderByExpr> = expressions
+                    .into_iter()
+                    .map(|expr| OrderByExpr {
+                        expr,
+                        asc: if asc { Some(asc) } else { None },
+                        nulls_first: if nulls_first { Some(nulls_first) } else { None },
+                    })
+                    .collect();
+
+                query.order_by.append(&mut order_expr);
+                Some(query)
+            }
+            None => {
+                return Err(ShellError::GenericError(
+                    "Connection without query".into(),
+                    "The connection needs a query defined".into(),
+                    Some(call.head),
+                    None,
+                    Vec::new(),
+                ))
+            }
+        };
+
+        Ok(db.into_value(call.head).into_pipeline_data())
+    }
+}

crates/nu-command/src/database/commands/select.rs

@@ -37,12 +37,12 @@ impl Command for ProjectionDb {
         vec![
             Example {
                 description: "selects a column from a database",
-                example: "db open db.mysql | db select a",
+                example: "db open db.mysql | db select a | db describe",
                 result: None,
             },
             Example {
                 description: "selects columns from a database",
-                example: "db open db.mysql | db select a b c",
+                example: "db open db.mysql | db select a b c | db describe",
                 result: None,
             },
         ]
@@ -86,18 +86,16 @@ fn create_query(expressions: Vec<SelectItem>) -> Query {
 
 fn modify_query(mut query: Query, expressions: Vec<SelectItem>) -> Query {
     query.body = match query.body {
-        SetExpr::Select(select) => SetExpr::Select(Box::new(modify_select(select, expressions))),
+        SetExpr::Select(select) => SetExpr::Select(modify_select(select, expressions)),
         _ => SetExpr::Select(Box::new(create_select(expressions))),
     };
 
     query
 }
 
-fn modify_select(select: Box<Select>, projection: Vec<SelectItem>) -> Select {
+fn modify_select(mut select: Box<Select>, projection: Vec<SelectItem>) -> Box<Select> {
-    Select {
+    select.as_mut().projection = projection;
-        projection,
+    select
-        ..select.as_ref().clone()
-    }
 }
 
 fn create_select(projection: Vec<SelectItem>) -> Select {

crates/nu-command/src/database/commands/where_.rs

@@ -0,0 +1,103 @@
+use crate::database::values::dsl::ExprDb;
+
+use super::super::SQLiteDatabase;
+use nu_engine::CallExt;
+use nu_protocol::{
+    ast::Call,
+    engine::{Command, EngineState, Stack},
+    Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, SyntaxShape, Value,
+};
+use sqlparser::ast::{Expr, Query, Select, SetExpr};
+
+#[derive(Clone)]
+pub struct WhereDb;
+
+impl Command for WhereDb {
+    fn name(&self) -> &str {
+        "db where"
+    }
+
+    fn usage(&self) -> &str {
+        "Includes a where statement for a query"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build(self.name())
+            .required("where", SyntaxShape::Any, "Where expression on the table")
+            .category(Category::Custom("database".into()))
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["database", "where"]
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "selects a column from a database with a where clause",
+            example: r#"db open db.mysql 
+    | db select a 
+    | db from table_1 
+    | db where ((db col a) > 1) 
+    | db describe"#,
+            result: None,
+        }]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let value: Value = call.req(engine_state, stack, 0)?;
+        let expr = ExprDb::try_from_value(&value)?.into_native();
+
+        let mut db = SQLiteDatabase::try_from_pipeline(input, call.head)?;
+        db.query = match db.query {
+            Some(query) => Some(modify_query(query, expr)),
+            None => {
+                return Err(ShellError::GenericError(
+                    "Connection without query".into(),
+                    "The connection needs a query defined".into(),
+                    Some(call.head),
+                    None,
+                    Vec::new(),
+                ))
+            }
+        };
+
+        Ok(db.into_value(call.head).into_pipeline_data())
+    }
+}
+
+fn modify_query(mut query: Query, expression: Expr) -> Query {
+    query.body = match query.body {
+        SetExpr::Select(select) => SetExpr::Select(modify_select(select, expression)),
+        _ => SetExpr::Select(Box::new(create_select(expression))),
+    };
+
+    query
+}
+
+fn modify_select(mut select: Box<Select>, expression: Expr) -> Box<Select> {
+    select.as_mut().selection = Some(expression);
+    select
+}
+
+fn create_select(expression: Expr) -> Select {
+    Select {
+        distinct: false,
+        top: None,
+        into: None,
+        projection: Vec::new(),
+        from: Vec::new(),
+        lateral_views: Vec::new(),
+        selection: Some(expression),
+        group_by: Vec::new(),
+        cluster_by: Vec::new(),
+        distribute_by: Vec::new(),
+        sort_by: Vec::new(),
+        having: None,
+    }
+}

crates/nu-command/src/database/expressions/alias.rs

@@ -1,11 +1,14 @@
-use crate::database::values::dsl::SelectDb;
+use crate::{
+    database::values::dsl::{ExprDb, SelectDb},
+    SQLiteDatabase,
+};
 use nu_engine::CallExt;
 use nu_protocol::{
     ast::Call,
     engine::{Command, EngineState, Stack},
     Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, SyntaxShape,
 };
-use sqlparser::ast::{Ident, SelectItem};
+use sqlparser::ast::{Ident, SelectItem, SetExpr, TableAlias, TableFactor};
 
 #[derive(Clone)]
 pub struct AliasExpr;
@@ -26,11 +29,22 @@ impl Command for AliasExpr {
     }
 
     fn examples(&self) -> Vec<Example> {
-        vec![Example {
+        vec![
-            description: "Creates an alias for a a column selection",
+            Example {
-            example: "db col name_a | db as new_a",
+                description: "Creates an alias for a column selection",
-            result: None,
+                example: "db col name_a | db as new_a",
-        }]
+                result: None,
+            },
+            Example {
+                description: "Creates an alias for a table",
+                example: r#"db open name 
+    | db select a 
+    | db from table_a 
+    | db as table_a_new 
+    | db describe"#,
+                result: None,
+            },
+        ]
     }
 
     fn search_terms(&self) -> Vec<&str> {
@@ -45,27 +59,95 @@ impl Command for AliasExpr {
         input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
         let alias: String = call.req(engine_state, stack, 0)?;
-        let select = SelectDb::try_from_pipeline(input, call.head)?;
+        let value = input.into_value(call.head);
 
-        let select = match select.into_native() {
+        if let Ok(expr) = ExprDb::try_from_value(&value) {
-            SelectItem::UnnamedExpr(expr) => SelectItem::ExprWithAlias {
+            alias_selection(expr.into_native().into(), alias, call)
-                expr,
+        } else if let Ok(select) = SelectDb::try_from_value(&value) {
-                alias: Ident {
+            alias_selection(select, alias, call)
-                    value: alias,
+        } else if let Ok(db) = SQLiteDatabase::try_from_value(value.clone()) {
-                    quote_style: None,
+            alias_db(db, alias, call)
-                },
+        } else {
-            },
+            Err(ShellError::CantConvert(
-            SelectItem::ExprWithAlias { expr, .. } => SelectItem::ExprWithAlias {
+                "expression or query".into(),
-                expr,
+                value.get_type().to_string(),
-                alias: Ident {
+                value.span()?,
-                    value: alias,
+                None,
-                    quote_style: None,
+            ))
-                },
+        }
-            },
+    }
-            select => select,
+}
-        };
+
-
+fn alias_selection(
-        let select: SelectDb = select.into();
+    select: SelectDb,
-        Ok(select.into_value(call.head).into_pipeline_data())
+    alias: String,
+    call: &Call,
+) -> Result<PipelineData, ShellError> {
+    let select = match select.into_native() {
+        SelectItem::UnnamedExpr(expr) => SelectItem::ExprWithAlias {
+            expr,
+            alias: Ident {
+                value: alias,
+                quote_style: None,
+            },
+        },
+        SelectItem::ExprWithAlias { expr, .. } => SelectItem::ExprWithAlias {
+            expr,
+            alias: Ident {
+                value: alias,
+                quote_style: None,
+            },
+        },
+        select => select,
+    };
+
+    let select: SelectDb = select.into();
+    Ok(select.into_value(call.head).into_pipeline_data())
+}
+
+fn alias_db(
+    mut db: SQLiteDatabase,
+    new_alias: String,
+    call: &Call,
+) -> Result<PipelineData, ShellError> {
+    match db.query {
+        None => Err(ShellError::GenericError(
+            "Error creating alias".into(),
+            "there is no query defined yet".into(),
+            Some(call.head),
+            None,
+            Vec::new(),
+        )),
+        Some(ref mut query) => match &mut query.body {
+            SetExpr::Select(ref mut select) => {
+                select.as_mut().from.iter_mut().for_each(|table| {
+                    let new_alias = Some(TableAlias {
+                        name: Ident {
+                            value: new_alias.clone(),
+                            quote_style: None,
+                        },
+                        columns: Vec::new(),
+                    });
+
+                    if let TableFactor::Table { ref mut alias, .. } = table.relation {
+                        *alias = new_alias;
+                    } else if let TableFactor::Derived { ref mut alias, .. } = table.relation {
+                        *alias = new_alias;
+                    } else if let TableFactor::TableFunction { ref mut alias, .. } = table.relation
+                    {
+                        *alias = new_alias;
+                    }
+                });
+
+                Ok(db.into_value(call.head).into_pipeline_data())
+            }
+            _ => Err(ShellError::GenericError(
+                "Error creating alias".into(),
+                "Query has no select from defined".into(),
+                Some(call.head),
+                None,
+                Vec::new(),
+            )),
+        },
     }
 }

crates/nu-command/src/database/expressions/col.rs

@@ -1,11 +1,10 @@
-use crate::database::values::dsl::{ExprDb, SelectDb};
+use crate::database::values::dsl::ExprDb;
 use nu_engine::CallExt;
 use nu_protocol::{
     ast::Call,
     engine::{Command, EngineState, Stack},
     Category, Example, IntoPipelineData, PipelineData, ShellError, Signature, SyntaxShape, Value,
 };
-use sqlparser::ast::{Ident, ObjectName, SelectItem};
 
 #[derive(Clone)]
 pub struct ColExpr;
@@ -44,28 +43,9 @@ impl Command for ColExpr {
         call: &Call,
         _input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        let name: Value = call.req(engine_state, stack, 0)?;
+        let value: Value = call.req(engine_state, stack, 0)?;
+        let expression = ExprDb::try_from_value(&value)?;
 
-        let select = match name {
+        Ok(expression.into_value(call.head).into_pipeline_data())
-            Value::String { val, .. } if val == "*" => SelectItem::Wildcard,
-            Value::String { val, .. } if val.contains('.') => {
-                let values = val
-                    .split('.')
-                    .map(|part| Ident {
-                        value: part.to_string(),
-                        quote_style: None,
-                    })
-                    .collect::<Vec<Ident>>();
-
-                SelectItem::QualifiedWildcard(ObjectName(values))
-            }
-            _ => {
-                let expr = ExprDb::try_from_value(name)?;
-                SelectItem::UnnamedExpr(expr.into_native())
-            }
-        };
-
-        let selection: SelectDb = select.into();
-        Ok(selection.into_value(call.head).into_pipeline_data())
     }
 }

crates/nu-command/src/database/values/dsl/expression.rs

@@ -1,7 +1,9 @@
-use nu_protocol::{CustomValue, ShellError, Span, Value};
+use nu_protocol::{
+    ast::{Operator, PathMember},
+    CustomValue, ShellError, Span, Type, Value,
+};
 use serde::{Deserialize, Serialize};
-
+use sqlparser::ast::{BinaryOperator, Expr, Ident};
-use sqlparser::ast::{Expr, Ident};
 
 #[derive(Debug, Serialize, Deserialize)]
 pub struct ExprDb(Expr);
@@ -47,6 +49,21 @@ impl CustomValue for ExprDb {
         self
     }
 
+    fn follow_path_int(&self, count: usize, span: Span) -> Result<Value, ShellError> {
+        let path = PathMember::Int { val: count, span };
+
+        ExprDb::expr_to_value(self.as_ref(), span).follow_cell_path(&[path])
+    }
+
+    fn follow_path_string(&self, column_name: String, span: Span) -> Result<Value, ShellError> {
+        let path = PathMember::String {
+            val: column_name,
+            span,
+        };
+
+        ExprDb::expr_to_value(self.as_ref(), span).follow_cell_path(&[path])
+    }
+
     fn typetag_name(&self) -> &'static str {
         "DB expresssion"
     }
@@ -54,25 +71,86 @@ impl CustomValue for ExprDb {
     fn typetag_deserialize(&self) {
         unimplemented!("typetag_deserialize")
     }
+
+    fn operation(
+        &self,
+        lhs_span: Span,
+        operator: Operator,
+        op: Span,
+        right: &Value,
+    ) -> Result<Value, ShellError> {
+        let right_expr = match right {
+            Value::CustomValue { .. } => ExprDb::try_from_value(right).map(ExprDb::into_native),
+            Value::String { val, .. } => Ok(Expr::Value(
+                sqlparser::ast::Value::SingleQuotedString(val.clone()),
+            )),
+            Value::Int { val, .. } => Ok(Expr::Value(sqlparser::ast::Value::Number(
+                format!("{}", val),
+                false,
+            ))),
+            Value::Bool { val, .. } => Ok(Expr::Value(sqlparser::ast::Value::Boolean(*val))),
+            _ => Err(ShellError::OperatorMismatch {
+                op_span: op,
+                lhs_ty: Type::Custom,
+                lhs_span,
+                rhs_ty: right.get_type(),
+                rhs_span: right.span()?,
+            }),
+        }?;
+
+        let sql_operator = match operator {
+            Operator::Equal => Ok(BinaryOperator::Eq),
+            Operator::NotEqual => Ok(BinaryOperator::NotEq),
+            Operator::LessThan => Ok(BinaryOperator::Lt),
+            Operator::GreaterThan => Ok(BinaryOperator::Gt),
+            Operator::LessThanOrEqual => Ok(BinaryOperator::LtEq),
+            Operator::GreaterThanOrEqual => Ok(BinaryOperator::GtEq),
+            Operator::RegexMatch => Ok(BinaryOperator::PGRegexMatch),
+            Operator::NotRegexMatch => Ok(BinaryOperator::PGRegexNotMatch),
+            Operator::Plus => Ok(BinaryOperator::Plus),
+            Operator::Minus => Ok(BinaryOperator::Minus),
+            Operator::Multiply => Ok(BinaryOperator::Multiply),
+            Operator::Divide => Ok(BinaryOperator::Divide),
+            Operator::Modulo => Ok(BinaryOperator::Modulo),
+            Operator::And => Ok(BinaryOperator::And),
+            Operator::Or => Ok(BinaryOperator::Or),
+            Operator::In
+            | Operator::NotIn
+            | Operator::Pow
+            | Operator::StartsWith
+            | Operator::EndsWith => Err(ShellError::UnsupportedOperator(operator, op)),
+        }?;
+
+        let expr = Expr::BinaryOp {
+            left: Box::new(self.as_ref().clone()),
+            op: sql_operator,
+            right: Box::new(right_expr),
+        };
+
+        Ok(ExprDb(expr).into_value(lhs_span))
+    }
 }
 
 impl ExprDb {
-    pub fn try_from_value(value: Value) -> Result<Self, ShellError> {
+    pub fn try_from_value(value: &Value) -> Result<Self, ShellError> {
         match value {
             Value::CustomValue { val, span } => match val.as_any().downcast_ref::<Self>() {
                 Some(expr) => Ok(Self(expr.0.clone())),
                 None => Err(ShellError::CantConvert(
                     "db expression".into(),
                     "non-expression".into(),
-                    span,
+                    *span,
                     None,
                 )),
             },
             Value::String { val, .. } => Ok(Expr::Identifier(Ident {
-                value: val,
+                value: val.clone(),
                 quote_style: None,
             })
             .into()),
+            Value::Int { val, .. } => {
+                Ok(Expr::Value(sqlparser::ast::Value::Number(format!("{}", val), false)).into())
+            }
             x => Err(ShellError::CantConvert(
                 "database".into(),
                 x.get_type().to_string(),
@@ -82,17 +160,12 @@ impl ExprDb {
         }
     }
 
-    // pub fn try_from_pipeline(input: PipelineData, span: Span) -> Result<Self, ShellError> {
+    pub fn into_value(self, span: Span) -> Value {
-    //     let value = input.into_value(span);
+        Value::CustomValue {
-    //     Self::try_from_value(value)
+            val: Box::new(self),
-    // }
+            span,
-
+        }
-    // pub fn into_value(self, span: Span) -> Value {
+    }
-    //     Value::CustomValue {
-    //         val: Box::new(self),
-    //         span,
-    //     }
-    // }
 
     pub fn into_native(self) -> Expr {
         self.0
@@ -101,6 +174,66 @@ impl ExprDb {
     pub fn to_value(&self, span: Span) -> Value {
         ExprDb::expr_to_value(self.as_ref(), span)
     }
+
+    // Convenient function to extrac multiple Expr that could be inside a nushell Value
+    pub fn extract_exprs(value: Value) -> Result<Vec<Expr>, ShellError> {
+        ExtractedExpr::extract_exprs(value).map(ExtractedExpr::into_exprs)
+    }
+}
+
+enum ExtractedExpr {
+    Single(Expr),
+    List(Vec<ExtractedExpr>),
+}
+
+impl ExtractedExpr {
+    fn into_exprs(self) -> Vec<Expr> {
+        match self {
+            Self::Single(expr) => vec![expr],
+            Self::List(exprs) => exprs
+                .into_iter()
+                .flat_map(ExtractedExpr::into_exprs)
+                .collect(),
+        }
+    }
+
+    fn extract_exprs(value: Value) -> Result<ExtractedExpr, ShellError> {
+        match value {
+            Value::String { val, .. } => {
+                let expr = Expr::Identifier(Ident {
+                    value: val,
+                    quote_style: None,
+                });
+
+                Ok(ExtractedExpr::Single(expr))
+            }
+            Value::Int { val, .. } => {
+                let expr = Expr::Value(sqlparser::ast::Value::Number(format!("{}", val), false));
+
+                Ok(ExtractedExpr::Single(expr))
+            }
+            Value::Bool { val, .. } => {
+                let expr = Expr::Value(sqlparser::ast::Value::Boolean(val));
+
+                Ok(ExtractedExpr::Single(expr))
+            }
+            Value::CustomValue { .. } => {
+                let expr = ExprDb::try_from_value(&value)?.into_native();
+                Ok(ExtractedExpr::Single(expr))
+            }
+            Value::List { vals, .. } => vals
+                .into_iter()
+                .map(Self::extract_exprs)
+                .collect::<Result<Vec<ExtractedExpr>, ShellError>>()
+                .map(ExtractedExpr::List),
+            x => Err(ShellError::CantConvert(
+                "selection".into(),
+                x.get_type().to_string(),
+                x.span()?,
+                None,
+            )),
+        }
+    }
 }
 
 impl ExprDb {
@@ -123,6 +256,24 @@ impl ExprDb {
                     span,
                 }
             }
+            Expr::Value(value) => Value::String {
+                val: format!("{}", value),
+                span,
+            },
+            Expr::BinaryOp { left, op, right } => {
+                let cols = vec!["left".into(), "op".into(), "right".into()];
+                let left = ExprDb::expr_to_value(left.as_ref(), span);
+                let right = ExprDb::expr_to_value(right.as_ref(), span);
+                let op = Value::String {
+                    val: format!("{}", op),
+                    span,
+                };
+
+                let vals = vec![left, op, right];
+
+                Value::Record { cols, vals, span }
+            }
+            Expr::Nested(expr) => ExprDb::expr_to_value(expr, span),
             Expr::CompoundIdentifier(_) => todo!(),
             Expr::IsNull(_) => todo!(),
             Expr::IsNotNull(_) => todo!(),
@@ -132,7 +283,6 @@ impl ExprDb {
             Expr::InSubquery { .. } => todo!(),
             Expr::InUnnest { .. } => todo!(),
             Expr::Between { .. } => todo!(),
-            Expr::BinaryOp { .. } => todo!(),
             Expr::UnaryOp { .. } => todo!(),
             Expr::Cast { .. } => todo!(),
             Expr::TryCast { .. } => todo!(),
@@ -140,8 +290,6 @@ impl ExprDb {
             Expr::Substring { .. } => todo!(),
             Expr::Trim { .. } => todo!(),
             Expr::Collate { .. } => todo!(),
-            Expr::Nested(_) => todo!(),
-            Expr::Value(_) => todo!(),
             Expr::TypedString { .. } => todo!(),
             Expr::MapAccess { .. } => todo!(),
             Expr::Function(_) => todo!(),

crates/nu-command/src/database/values/dsl/select_item.rs

@@ -1,7 +1,7 @@
 use super::ExprDb;
-use nu_protocol::{ast::PathMember, CustomValue, PipelineData, ShellError, Span, Value};
+use nu_protocol::{ast::PathMember, CustomValue, ShellError, Span, Value};
 use serde::{Deserialize, Serialize};
-use sqlparser::ast::{Expr, Ident, SelectItem};
+use sqlparser::ast::{Expr, Ident, ObjectName, SelectItem};
 
 #[derive(Debug, Serialize, Deserialize)]
 pub struct SelectDb(SelectItem);
@@ -20,8 +20,14 @@ impl AsMut<SelectItem> for SelectDb {
 }
 
 impl From<SelectItem> for SelectDb {
-    fn from(expr: SelectItem) -> Self {
+    fn from(selection: SelectItem) -> Self {
-        Self(expr)
+        Self(selection)
+    }
+}
+
+impl From<Expr> for SelectDb {
+    fn from(expr: Expr) -> Self {
+        SelectItem::UnnamedExpr(expr).into()
     }
 }
 
@@ -71,25 +77,52 @@ impl CustomValue for SelectDb {
 }
 
 impl SelectDb {
-    pub fn try_from_value(value: Value) -> Result<Self, ShellError> {
+    pub fn try_from_value(value: &Value) -> Result<Self, ShellError> {
         match value {
             Value::CustomValue { val, span } => match val.as_any().downcast_ref::<Self>() {
                 Some(expr) => Ok(Self(expr.0.clone())),
                 None => Err(ShellError::CantConvert(
-                    "db expression".into(),
+                    "db selection".into(),
                     "non-expression".into(),
-                    span,
+                    *span,
                     None,
                 )),
             },
-            Value::String { val, .. } => {
+            Value::String { val, .. } => match val.as_str() {
-                let expr = Expr::Identifier(Ident {
+                "*" => Ok(SelectItem::Wildcard.into()),
-                    value: val,
+                name if (name.contains('.') && name.contains('*')) => {
-                    quote_style: None,
+                    let parts: Vec<Ident> = name
-                });
+                        .split('.')
+                        .filter(|part| part != &"*")
+                        .map(|part| Ident {
+                            value: part.to_string(),
+                            quote_style: None,
+                        })
+                        .collect();
 
-                Ok(SelectItem::UnnamedExpr(expr).into())
+                    Ok(SelectItem::QualifiedWildcard(ObjectName(parts)).into())
-            }
+                }
+                name if name.contains('.') => {
+                    let parts: Vec<Ident> = name
+                        .split('.')
+                        .map(|part| Ident {
+                            value: part.to_string(),
+                            quote_style: None,
+                        })
+                        .collect();
+
+                    let expr = Expr::CompoundIdentifier(parts);
+                    Ok(SelectItem::UnnamedExpr(expr).into())
+                }
+                _ => {
+                    let expr = Expr::Identifier(Ident {
+                        value: val.clone(),
+                        quote_style: None,
+                    });
+
+                    Ok(SelectItem::UnnamedExpr(expr).into())
+                }
+            },
             x => Err(ShellError::CantConvert(
                 "selection".into(),
                 x.get_type().to_string(),
@@ -99,11 +132,6 @@ impl SelectDb {
         }
     }
 
-    pub fn try_from_pipeline(input: PipelineData, span: Span) -> Result<Self, ShellError> {
-        let value = input.into_value(span);
-        Self::try_from_value(value)
-    }
-
     pub fn into_value(self, span: Span) -> Value {
         Value::CustomValue {
             val: Box::new(self),
@@ -203,16 +231,29 @@ impl ExtractedSelect {
 
                 Ok(ExtractedSelect::Single(SelectItem::UnnamedExpr(expr)))
             }
-            Value::CustomValue { .. } => SelectDb::try_from_value(value)
+            Value::CustomValue { .. } => {
-                .map(SelectDb::into_native)
+                if let Ok(expr) = ExprDb::try_from_value(&value) {
-                .map(ExtractedSelect::Single),
+                    Ok(ExtractedSelect::Single(SelectItem::UnnamedExpr(
+                        expr.into_native(),
+                    )))
+                } else if let Ok(select) = SelectDb::try_from_value(&value) {
+                    Ok(ExtractedSelect::Single(select.into_native()))
+                } else {
+                    Err(ShellError::CantConvert(
+                        "selection".into(),
+                        value.get_type().to_string(),
+                        value.span()?,
+                        None,
+                    ))
+                }
+            }
             Value::List { vals, .. } => vals
                 .into_iter()
                 .map(Self::extract_selects)
                 .collect::<Result<Vec<ExtractedSelect>, ShellError>>()
                 .map(ExtractedSelect::List),
             x => Err(ShellError::CantConvert(
-                "expression".into(),
+                "selection".into(),
                 x.get_type().to_string(),
                 x.span()?,
                 None,