Add delete from query documentation

Author: sclubricants

tests/system/Database/Live/DeleteTest.php

@@ -12,6 +12,7 @@
 namespace CodeIgniter\Database\Live;
 
 use CodeIgniter\Database\Exceptions\DatabaseException;
+use CodeIgniter\Database\Forge;
 use CodeIgniter\Test\CIUnitTestCase;
 use CodeIgniter\Test\DatabaseTestTrait;
 use Config\Database;
@@ -26,6 +27,11 @@ final class DeleteTest extends CIUnitTestCase
 {
     use DatabaseTestTrait;
 
+    /**
+     * @var Forge|mixed
+     */
+    public $forge;
+
     protected $refresh = true;
     protected $seed    = CITestSeeder::class;
 
@@ -145,7 +151,7 @@ public function testDeleteBatchWithQuery()
         $this->seeInDatabase('user', ['name' => 'Ahmadinejad', 'email' => 'ahmadinejad@world.com']);
         $this->dontSeeInDatabase('user', ['name' => 'Chris Martin', 'email' => 'chris@world.com']);
 
-        $result = $this->db->table('user')->get()->getResultArray();
+        $this->db->table('user')->get()->getResultArray();
 
         $this->forge->dropTable('user2', true);
     }

user_guide_src/source/database/query_builder.rst

@@ -1140,6 +1140,10 @@ This method may be especially useful when deleting data in a table with a compos
 
 .. note:: SQLite does not support the use of ``where()``.
 
+You can also delete from a query:
+
+.. literalinclude:: query_builder/119.php
+
 $builder->emptyTable()
 ----------------------
 

user_guide_src/source/database/query_builder/119.php

@@ -0,0 +1,21 @@
+<?php
+
+use CodeIgniter\Database\RawSql;
+
+$query = $this->db->table('user2')->select('email, name, country')->where('country', 'Greece');
+
+$this->db->table('user')
+    ->setQueryAsData($query, 'alias')
+    ->onConstraint('email')
+    ->where('alias.name = user.name')
+    ->deleteBatch();
+
+/* MySQLi produces:
+    DELETE `user` FROM `user`
+    INNER JOIN (
+    SELECT `email`, `name`, `country`
+    FROM `user2`
+    WHERE `country` = 'Greece') `alias`
+    ON `user`.`email` = `alias`.`email`
+    WHERE `alias`.`name` = `user`.`name`
+*/