Merge pull request #24 from ejyager00/subquery-join

Allow use of subqueries in join clauses

Author: G4brym

src/Builder.ts

@@ -204,7 +204,11 @@ export class QueryBuilder<GenericResult, GenericResultOne> {
     const joinQuery: Array<string> = []
     value.forEach((item: Join) => {
       const type = item.type ? `${item.type} ` : ''
-      joinQuery.push(`${type}JOIN ${item.table} ON ${item.on}`)
+      joinQuery.push(
+        `${type}JOIN ${typeof item.table === 'string' ? item.table : `(${this._select(item.table)})`}${
+          item.alias ? ` AS ${item.alias}` : ''
+        } ON ${item.on}`
+      )
     })
 
     return ' ' + joinQuery.join(' ')

src/interfaces.ts

@@ -9,8 +9,9 @@ export interface Where {
 
 export interface Join {
   type?: string | JoinTypes
-  table: string
+  table: string | SelectAll
   on: string
+  alias?: string
 }
 
 export interface SelectOne {

test/Builder.test.ts

@@ -444,6 +444,67 @@ describe('QueryBuilder', () => {
     )
   })
 
+  test('select with subquery join', async () => {
+    const query = new QuerybuilderTest()._select({
+      tableName: 'testTable',
+      fields: '*',
+      where: {
+        conditions: 'field = ?1',
+        params: ['test'],
+      },
+      join: {
+        table: {
+          tableName: 'otherTable',
+          fields: ['test_table_id', 'GROUP_CONCAT(attribute) AS attributes'],
+          groupBy: 'test_table_id',
+        },
+        on: 'testTable.id = otherTableGrouped.test_table_id',
+        alias: 'otherTableGrouped',
+      },
+    })
+
+    expect(query).toEqual(
+      'SELECT * FROM testTable JOIN (SELECT test_table_id, GROUP_CONCAT(attribute) AS attributes FROM otherTable GROUP BY test_table_id) AS otherTableGrouped ON testTable.id = otherTableGrouped.test_table_id WHERE field = ?1'
+    )
+  })
+
+  test('select with nested subquery joins', async () => {
+    const query = new QuerybuilderTest()._select({
+      tableName: 'testTable',
+      fields: '*',
+      where: {
+        conditions: 'field = ?1',
+        params: ['test'],
+      },
+      join: {
+        table: {
+          tableName: 'otherTable',
+          fields: [
+            'test_table_id',
+            'GROUP_CONCAT(attribute) AS attributes',
+            'GROUP_CONCAT(other_attributes, ";") AS other_attributes',
+          ],
+          groupBy: 'test_table_id',
+          join: {
+            table: {
+              tableName: 'otherTableTwo',
+              fields: ['other_table_id', 'GROUP_CONCAT(other_attribute) AS other_attributes'],
+              groupBy: 'other_table_id',
+            },
+            on: 'otherTable.id = otherTableTwoGrouped.other_table_id',
+            alias: 'otherTableTwoGrouped',
+          },
+        },
+        on: 'testTable.id = otherTableGrouped.test_table_id',
+        alias: 'otherTableGrouped',
+      },
+    })
+
+    expect(query).toEqual(
+      'SELECT * FROM testTable JOIN (SELECT test_table_id, GROUP_CONCAT(attribute) AS attributes, GROUP_CONCAT(other_attributes, ";") AS other_attributes FROM otherTable JOIN (SELECT other_table_id, GROUP_CONCAT(other_attribute) AS other_attributes FROM otherTableTwo GROUP BY other_table_id) AS otherTableTwoGrouped ON otherTable.id = otherTableTwoGrouped.other_table_id GROUP BY test_table_id) AS otherTableGrouped ON testTable.id = otherTableGrouped.test_table_id WHERE field = ?1'
+    )
+  })
+
   test('select with one where no parameters', async () => {
     const query = new QuerybuilderTest()._select({
       tableName: 'testTable',