Support select queries without from clause (#605)

* support select queries without from clause

* rename select --> selectNoFrom

src/expression/expression-builder.ts

@@ -65,6 +65,12 @@ import { JSONPathBuilder } from '../query-builder/json-path-builder.js'
 import { OperandExpression } from '../parser/expression-parser.js'
 import { BinaryOperationNode } from '../operation-node/binary-operation-node.js'
 import { AndNode } from '../operation-node/and-node.js'
+import {
+  SelectArg,
+  SelectExpression,
+  Selection,
+  parseSelectArg,
+} from '../parser/select-parser.js'
 
 export interface ExpressionBuilder<DB, TB extends keyof DB> {
   /**
@@ -250,6 +256,19 @@ export interface ExpressionBuilder<DB, TB extends keyof DB> {
     from: TE
   ): SelectQueryBuilder<From<DB, TE>, FromTables<DB, TB, TE>, {}>
 
+  /**
+   * Creates a `select` expression without a `from` clause.
+   *
+   * If you want to create a `select from` query, use the `selectFrom` method instead.
+   * This one can be used to create a plain `select` statement without a `from` clause.
+   *
+   * This method accepts the same inputs as {@link SelectQueryBuilder.select}. See its
+   * documentation for examples.
+   */
+  selectNoFrom<SE extends SelectExpression<DB, TB>>(
+    selection: SelectArg<DB, TB, SE>
+  ): SelectQueryBuilder<DB, TB, Selection<DB, TB, SE>>
+
   /**
    * Creates a `case` statement/operator.
    *
@@ -852,8 +871,23 @@ export function createExpressionBuilder<DB, TB extends keyof DB>(
     selectFrom(table: TableExpressionOrList<DB, TB>): any {
       return createSelectQueryBuilder({
         queryId: createQueryId(),
-        executor: executor,
-        queryNode: SelectQueryNode.create(parseTableExpressionOrList(table)),
+        executor,
+        queryNode: SelectQueryNode.createFrom(
+          parseTableExpressionOrList(table)
+        ),
+      })
+    },
+
+    selectNoFrom<SE extends SelectExpression<DB, TB>>(
+      selection: SelectArg<DB, TB, SE>
+    ): SelectQueryBuilder<DB, TB, Selection<DB, TB, SE>> {
+      return createSelectQueryBuilder({
+        queryId: createQueryId(),
+        executor,
+        queryNode: SelectQueryNode.cloneWithSelections(
+          SelectQueryNode.create(),
+          parseSelectArg(selection)
+        ),
       })
     },
 

src/operation-node/select-query-node.ts

@@ -18,7 +18,7 @@ import { SetOperationNode } from './set-operation-node.js'
 
 export interface SelectQueryNode extends OperationNode {
   readonly kind: 'SelectQueryNode'
-  readonly from: FromNode
+  readonly from?: FromNode
   readonly selections?: ReadonlyArray<SelectionNode>
   readonly distinctOn?: ReadonlyArray<OperationNode>
   readonly joins?: ReadonlyArray<JoinNode>
@@ -43,7 +43,14 @@ export const SelectQueryNode = freeze({
     return node.kind === 'SelectQueryNode'
   },
 
-  create(
+  create(withNode?: WithNode): SelectQueryNode {
+    return freeze({
+      kind: 'SelectQueryNode',
+      ...(withNode && { with: withNode }),
+    })
+  },
+
+  createFrom(
     fromItems: ReadonlyArray<OperationNode>,
     withNode?: WithNode
   ): SelectQueryNode {

src/parser/parse-utils.ts

@@ -20,7 +20,7 @@ export function createSelectQueryBuilder(): SelectQueryBuilder<any, any, any> {
   return newSelectQueryBuilder({
     queryId: createQueryId(),
     executor: NOOP_QUERY_EXECUTOR,
-    queryNode: SelectQueryNode.create(parseTableExpressionOrList([])),
+    queryNode: SelectQueryNode.createFrom(parseTableExpressionOrList([])),
   })
 }
 

src/plugin/camel-case/camel-case-plugin.ts

@@ -1,12 +1,6 @@
 import { QueryResult } from '../../driver/database-connection.js'
 import { RootOperationNode } from '../../query-compiler/query-compiler.js'
-import {
-  isArrayBufferOrView,
-  isBuffer,
-  isDate,
-  isObject,
-  isPlainObject,
-} from '../../util/object-utils.js'
+import { isPlainObject } from '../../util/object-utils.js'
 import { UnknownRow } from '../../util/type-utils.js'
 import {
   KyselyPlugin,
@@ -97,9 +91,9 @@ export interface CamelCasePluginOptions {
  * ```
  *
  * As you can see from the example, __everything__ needs to be defined
- * in camelCase in the typescript code: the table names, the columns,
- * schemas, __everything__. When using the `CamelCasePlugin` Kysely
- * works as if the database was defined in camelCase.
+ * in camelCase in the typescript code: table names, columns, schemas,
+ * __everything__. When using the `CamelCasePlugin` Kysely works as if
+ * the database was defined in camelCase.
  *
  * There are various options you can give to the plugin to modify
  * the way identifiers are converted. See {@link CamelCasePluginOptions}.

src/query-compiler/default-query-compiler.ts

@@ -151,24 +151,27 @@ export class DefaultQueryCompiler
       this.append(' ')
     }
 
-    this.append('select ')
+    this.append('select')
 
     if (node.distinctOn) {
-      this.compileDistinctOn(node.distinctOn)
       this.append(' ')
+      this.compileDistinctOn(node.distinctOn)
     }
 
-    if (node.frontModifiers && node.frontModifiers.length > 0) {
-      this.compileList(node.frontModifiers, ' ')
+    if (node.frontModifiers?.length) {
       this.append(' ')
+      this.compileList(node.frontModifiers, ' ')
     }
 
     if (node.selections) {
-      this.compileList(node.selections)
       this.append(' ')
+      this.compileList(node.selections)
     }
 
-    this.visitNode(node.from)
+    if (node.from) {
+      this.append(' ')
+      this.visitNode(node.from)
+    }
 
     if (node.joins) {
       this.append(' ')
@@ -210,7 +213,7 @@ export class DefaultQueryCompiler
       this.visitNode(node.offset)
     }
 
-    if (node.endModifiers && node.endModifiers.length > 0) {
+    if (node.endModifiers?.length) {
       this.append(' ')
       this.compileList(node.endModifiers, ' ')
     }
@@ -944,7 +947,7 @@ export class DefaultQueryCompiler
       if (!node.materialized) {
         this.append('not ')
       }
-      
+
       this.append('materialized ')
     }
 

src/query-creator.ts

@@ -39,6 +39,12 @@ import { DeleteResult } from './query-builder/delete-result.js'
 import { UpdateResult } from './query-builder/update-result.js'
 import { KyselyPlugin } from './plugin/kysely-plugin.js'
 import { CTEBuilderCallback } from './query-builder/cte-builder.js'
+import {
+  SelectArg,
+  SelectExpression,
+  Selection,
+  parseSelectArg,
+} from './parser/select-parser.js'
 
 export class QueryCreator<DB> {
   readonly #props: QueryCreatorProps
@@ -182,13 +188,73 @@ export class QueryCreator<DB> {
     return createSelectQueryBuilder({
       queryId: createQueryId(),
       executor: this.#props.executor,
-      queryNode: SelectQueryNode.create(
+      queryNode: SelectQueryNode.createFrom(
         parseTableExpressionOrList(from),
         this.#props.withNode
       ),
     })
   }
 
+  /**
+   * Creates a `select` query builder without a `from` clause.
+   *
+   * If you want to create a `select from` query, use the `selectFrom` method instead.
+   * This one can be used to create a plain `select` statement without a `from` clause.
+   *
+   * This method accepts the same inputs as {@link SelectQueryBuilder.select}. See its
+   * documentation for more examples.
+   *
+   * ### Examples
+   *
+   * ```ts
+   * const result = db.select((eb) => [
+   *   eb.selectFrom('person')
+   *     .select('id')
+   *     .where('first_name', '=', 'Jennifer')
+   *     .limit(1)
+   *     .as('jennifer_id'),
+   *
+   *   eb.selectFrom('pet')
+   *     .select('id')
+   *     .where('name', '=', 'Doggo')
+   *     .limit(1)
+   *     .as('doggo_id')
+   *   ])
+   *   .executeTakeFirstOrThrow()
+   *
+   * console.log(result.jennifer_id)
+   * console.log(result.doggo_id)
+   * ```
+   *
+   * The generated SQL (PostgreSQL):
+   *
+   * ```sql
+   * select (
+   *   select "id"
+   *   from "person"
+   *   where "first_name" = $1
+   *   limit $2
+   * ) as "jennifer_id", (
+   *   select "id"
+   *   from "pet"
+   *   where "name" = $3
+   *   limit $4
+   * ) as "doggo_id"
+   * ```
+   */
+  selectNoFrom<SE extends SelectExpression<DB, never>>(
+    selection: SelectArg<DB, never, SE>
+  ): SelectQueryBuilder<DB, never, Selection<DB, never, SE>> {
+    return createSelectQueryBuilder({
+      queryId: createQueryId(),
+      executor: this.#props.executor,
+      queryNode: SelectQueryNode.cloneWithSelections(
+        SelectQueryNode.create(this.#props.withNode),
+        parseSelectArg(selection as any)
+      ),
+    })
+  }
+
   /**
    * Creates an insert query.
    *

test/node/src/select.test.ts

@@ -848,6 +848,43 @@ for (const dialect of DIALECTS) {
       }
     }
 
+    it('should create a select statement without a `from` clause', async () => {
+      const query = ctx.db.selectNoFrom((eb) => [
+        eb.selectNoFrom(eb.lit(1).as('one')).as('one'),
+        eb
+          .selectFrom('person')
+          .select('first_name')
+          .orderBy('first_name')
+          .limit(1)
+          .as('person_first_name'),
+      ])
+
+      testSql(query, dialect, {
+        postgres: {
+          sql: `select (select 1 as "one") as "one", (select "first_name" from "person" order by "first_name" limit $1) as "person_first_name"`,
+          parameters: [1],
+        },
+        mysql: {
+          sql: 'select (select 1 as `one`) as `one`, (select `first_name` from `person` order by `first_name` limit ?) as `person_first_name`',
+          parameters: [1],
+        },
+        sqlite: {
+          sql: 'select (select 1 as "one") as "one", (select "first_name" from "person" order by "first_name" limit ?) as "person_first_name"',
+          parameters: [1],
+        },
+      })
+
+      const result = await query.execute()
+      expect(result).to.have.length(1)
+
+      if (dialect === 'mysql') {
+        // For some weird reason, MySQL returns `one` as a string.
+        expect(result[0]).to.eql({ one: '1', person_first_name: 'Arnold' })
+      } else {
+        expect(result[0]).to.eql({ one: 1, person_first_name: 'Arnold' })
+      }
+    })
+
     it.skip('perf', async () => {
       const ids = Array.from({ length: 100 }).map(() =>
         Math.round(Math.random() * 1000)

test/typings/test-d/expression.test-d.ts

@@ -25,7 +25,9 @@ function testExpression(db: Kysely<Database>) {
   )
 }
 
-function testExpressionBuilder(eb: ExpressionBuilder<Database, 'person'>) {
+async function testExpressionBuilder(
+  eb: ExpressionBuilder<Database, 'person'>
+) {
   // Binary expression
   expectAssignable<Expression<number>>(eb('age', '+', 1))
 
@@ -143,3 +145,44 @@ function testExpressionBuilder(eb: ExpressionBuilder<Database, 'person'>) {
   expectError(eb.betweenSymmetric('age', 'wrong type', 2))
   expectError(eb.betweenSymmetric('age', 1, 'wrong type'))
 }
+
+async function testExpressionBuilderSelect(
+  db: Kysely<Database>,
+  eb: ExpressionBuilder<Database, 'person'>
+) {
+  expectAssignable<Expression<{ first_name: string }>>(
+    eb.selectNoFrom(eb.val('Jennifer').as('first_name'))
+  )
+
+  expectAssignable<Expression<{ first_name: string }>>(
+    eb.selectNoFrom((eb) => eb.val('Jennifer').as('first_name'))
+  )
+
+  expectAssignable<Expression<{ first_name: string; last_name: string }>>(
+    eb.selectNoFrom([
+      eb.val('Jennifer').as('first_name'),
+      eb(eb.val('Anis'), '||', eb.val('ton')).as('last_name'),
+    ])
+  )
+
+  expectAssignable<
+    Expression<{ first_name: string; last_name: string | null }>
+  >(
+    eb.selectNoFrom((eb) => [
+      eb.val('Jennifer').as('first_name'),
+      eb.selectFrom('person').select('last_name').limit(1).as('last_name'),
+    ])
+  )
+
+  const r1 = await db
+    .selectFrom('person as p')
+    .select((eb) => [eb.selectNoFrom('p.age').as('age')])
+    .executeTakeFirstOrThrow()
+  expectType<{ age: number | null }>(r1)
+
+  expectError(
+    db
+      .selectFrom('person')
+      .select((eb) => [eb.selectNoFrom('pet.name').as('name')])
+  )
+}

test/typings/test-d/select-no-from.test-d.ts

@@ -0,0 +1,31 @@
+import { Kysely, SqlBool, sql } from '..'
+import { Database } from '../shared'
+import { expectType } from 'tsd'
+
+async function testSelectNoFrom(db: Kysely<Database>) {
+  const r1 = await db
+    .selectNoFrom(sql<'bar'>`select 'bar'`.as('foo'))
+    .executeTakeFirstOrThrow()
+  expectType<{ foo: 'bar' }>(r1)
+
+  const r2 = await db
+    .selectNoFrom((eb) => eb(eb.val(1), '=', 1).as('very_useful'))
+    .executeTakeFirstOrThrow()
+  expectType<{ very_useful: SqlBool }>(r2)
+
+  const r3 = await db
+    .selectNoFrom([
+      sql<'bar'>`select 'bar'`.as('foo'),
+      db.selectFrom('pet').select('id').limit(1).as('pet_id'),
+    ])
+    .executeTakeFirstOrThrow()
+  expectType<{ foo: 'bar'; pet_id: string | null }>(r3)
+
+  const r4 = await db
+    .selectNoFrom((eb) => [
+      eb(eb.val(1), '=', 1).as('very_useful'),
+      eb.selectFrom('pet').select('id').limit(1).as('pet_id'),
+    ])
+    .executeTakeFirstOrThrow()
+  expectType<{ very_useful: SqlBool; pet_id: string | null }>(r4)
+}