diff --git a/packages/core/src/selection.ts b/packages/core/src/selection.ts
index aab3421f..655f3e54 100644
--- a/packages/core/src/selection.ts
+++ b/packages/core/src/selection.ts
@@ -1,4 +1,4 @@
-import { defineProperty, Dict, filterKeys, valueMap } from 'cosmokit'
+import { defineProperty, Dict, filterKeys, mapValues, valueMap } from 'cosmokit'
 import { Driver } from './driver.ts'
 import { Eval, executeEval } from './eval.ts'
 import { Model } from './model.ts'
@@ -235,6 +235,30 @@ export class Selection<S = any> extends Executable<S, S[]> {
     return new Selection(this.driver, this)
   }
 
+  join<K extends string, U>(
+    name: K,
+    selection: Selection<U>,
+    callback: (self: Row<S>, other: Row<U>) => Eval.Expr<boolean> = () => Eval.and(),
+    type: 'inner' | 'left' | 'right' = 'inner',
+  ): Selection<S & { [P in K]: U}> {
+    const fields = Object.fromEntries(Object.entries(this.model.fields)
+      .filter(([, field]) => !field!.deprecated)
+      .map(([key]) => [key, (row) => key.split('.').reduce((r, k) => r[k], row[this.ref])]))
+    if (type === 'left') {
+      return this.driver.database
+        .join({ [this.ref]: this as Selection, [name]: selection }, (t: any) => callback(t[this.ref], t[name]), { [this.ref]: false, [name]: true })
+        .project({ ...fields, [name]: name }) as any
+    } else if (type === 'right') {
+      return this.driver.database
+        .join({ [name]: selection, [this.ref]: this as Selection }, (t: any) => callback(t[this.ref], t[name]), { [name]: true, [this.ref]: false })
+        .project({ ...fields, [name]: name }) as any
+    } else {
+      return this.driver.database
+        .join({ [this.ref]: this as Selection, [name]: selection }, (t: any) => callback(t[this.ref], t[name]))
+        .project({ ...fields, [name]: name }) as any
+    }
+  }
+
   _action(type: Executable.Action, ...args: any[]) {
     return new Executable(this.driver, { ...this, type, args })
   }
@@ -278,6 +302,14 @@ export class Selection<S = any> extends Executable<S, S[]> {
       })
     })
   }
+
+  format(result = {}) {
+    result['ref'] = this.ref
+    if (typeof this.table === 'string') result['table'] = this.table
+    else if (this.table instanceof Selection) result['table'] = this.table.format()
+    else result['table'] = mapValues(this.table, (v: any) => v.format())
+    return result
+  }
 }
 
 export function executeSort(data: any[], modifier: Modifier, name: string) {
diff --git a/packages/tests/src/selection.ts b/packages/tests/src/selection.ts
index 4e7bc4a8..1ab5d3fc 100644
--- a/packages/tests/src/selection.ts
+++ b/packages/tests/src/selection.ts
@@ -285,6 +285,11 @@ namespace SelectionTests {
         .join(['foo', 'bar'], (foo, bar) => $.eq(foo.value, bar.value))
         .execute()
       ).to.eventually.have.length(2)
+
+      await expect(database.select('foo')
+        .join('bar', database.select('bar'), (foo, bar) => $.eq(foo.value, bar.value))
+        .execute()
+      ).to.eventually.have.length(2)
     })
 
     it('left join', async () => {
@@ -303,6 +308,30 @@ namespace SelectionTests {
         { foo: { value: 2, id: 2 }, bar: {} },
         { foo: { value: 2, id: 3 }, bar: {} },
       ])
+
+      await expect(database.select('foo')
+        .join('bar', database.select('bar'), (foo, bar) => $.eq(foo.value, bar.value), 'left')
+        .execute()
+      ).to.eventually.have.shape([
+        {
+          value: 0, id: 1,
+          bar: { uid: 1, pid: 1, value: 0, id: 1 },
+        },
+        {
+          value: 0, id: 1,
+          bar: { uid: 1, pid: 2, value: 0, id: 3 },
+        },
+        { value: 2, id: 2, bar: {} },
+        { value: 2, id: 3, bar: {} },
+      ])
+    })
+
+    it('duplicate', async () => {
+      await expect(database.select('foo')
+        .project(['value'])
+        .join('bar', database.select('bar'), (foo, bar) => $.eq(foo.value, bar.uid))
+        .execute()
+      ).to.eventually.have.length(4)
     })
 
     it('group', async () => {
@@ -344,6 +373,12 @@ namespace SelectionTests {
         }, ({ t1, t2, t3 }) => $.gt($.add(t1.id, t2.id, t3.id), 14))
         .execute()
       ).to.eventually.have.length(4)
+
+      await expect(database.select('bar').where(row => $.gt(row.pid, 1))
+        .join('t2', database.select('bar').where(row => $.gt(row.uid, 1)))
+        .join('t3', database.select('bar').where(row => $.gt(row.id, 4)), (self, t3) => $.gt($.add(self.id, self.t2.id, t3.id), 14))
+        .execute()
+      ).to.eventually.have.length(4)
     })
 
     it('aggregate', async () => {