Removed Cross Join Clause

Author: Daniel Opitz

docs/readme.md

@@ -230,22 +230,14 @@ LEFT JOIN `posts` ON `users`.`id` = `posts`.`user_id`;
 
 #### Cross Join Clause
 
-To perform a "cross join" use the crossJoin method with the name of the table you wish to cross join to. 
-Cross joins generate a cartesian product between the first table and the joined table:
+From the [MySQL JOIN](https://dev.mysql.com/doc/refman/5.7/en/nested-join-optimization.html) docs:
 
-```php
-$users = $this->select()
-    ->from('sizes')
-    ->crossJoin('posts', 'users.id', '=', 'posts.user_id')
-    ->execute()
-    ->fetchAll();
-```
+> In MySQL, CROSS JOIN is syntactically equivalent to INNER JOIN; they can replace each other. 
+> In standard SQL, they are not equivalent. INNER JOIN is used with an ON clause; CROSS JOIN is used otherwise.
 
-```sql
-SELECT *
-FROM `users`
-CROSS JOIN `posts` ON `users`.`id` = `posts`.`user_id`;
-```
+In MySQL Inner Join and Cross Join yielding the same result.
+
+Please use the [join](#inner-join-clause) method.
 
 #### Advanced Join Clauses
 
@@ -262,7 +254,8 @@ $users = $this->select()
 ```
 
 ```sql
-SELECT `id` FROM `users` AS `u` INNER JOIN `posts` AS `p` ON (p.user_id=u.id AND u.enabled=1 OR p.published IS NULL);
+SELECT `id` FROM `users` AS `u` 
+INNER JOIN `posts` AS `p` ON (p.user_id=u.id AND u.enabled=1 OR p.published IS NULL);
 ```
 
 ### Unions

src/Database/SelectQuery.php

@@ -218,22 +218,6 @@ public function leftJoin(string $table, string $leftField, string $comparison, $
         return $this;
     }
 
-    /**
-     * Cross Join.
-     *
-     * @param string $table Table name
-     * @param string $leftField Name of the left field
-     * @param string $comparison Comparison (=,<,>,<=,>=,<>,in, not in, between, not between)
-     * @param mixed $rightField Value of the right field
-     * @return self
-     */
-    public function crossJoin(string $table, string $leftField, string $comparison, $rightField): self
-    {
-        $this->join[] = ['cross', $table, $leftField, $comparison, $rightField];
-
-        return $this;
-    }
-
     /**
      * Join with complex conditions.
      *
@@ -262,20 +246,6 @@ public function leftJoinRaw(string $table, RawExp $raw): self
         return $this;
     }
 
-    /**
-     * Cross join with complex conditions.
-     *
-     * @param string $table Table name
-     * @param RawExp $raw
-     * @return self
-     */
-    public function crossJoinRaw(string $table, RawExp $raw): self
-    {
-        $this->join[] = ['cross', $table, $raw, null, null, null];
-
-        return $this;
-    }
-
     /**
      * Where AND condition.
      *

tests/SelectQueryTest.php

@@ -622,25 +622,6 @@ public function testLeftJoinRaw()
         $this->assertSame("SELECT `id` FROM `test` LEFT JOIN `users` `u` ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c OR t2.b IS NULL);", $select->build());
     }
 
-    /**
-     * Test
-     *
-     * @covers ::crossJoinRaw
-     * @covers ::getJoinSql
-     * @covers ::from
-     * @covers ::prepare
-     * @covers ::build
-     */
-    public function testCrossJoinRaw()
-    {
-        $select = $this->select()
-            ->columns('id')
-            ->from('test')
-            ->crossJoinRaw('users u', new RawExp('t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c OR t2.b IS NULL'));
-        $this->assertInstanceOf(PDOStatement::class, $select->prepare());
-        $this->assertSame("SELECT `id` FROM `test` CROSS JOIN `users` `u` ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c OR t2.b IS NULL);", $select->build());
-    }
-
     /**
      * Test
      *
@@ -664,34 +645,6 @@ public function testLeftJoin()
         $this->assertSame($expected, $select->build());
     }
 
-    /**
-     * Test
-     *
-     * @covers ::crossJoin
-     * @covers ::getJoinSql
-     * @covers ::leftJoin
-     * @covers ::from
-     * @covers ::prepare
-     * @covers ::build
-     */
-    public function testCrossJoin()
-    {
-        $select = $this->select()
-            ->columns('id')
-            ->from('test')
-            ->crossJoin('users u', 'u.id', '=', 'test.user_id');
-        $this->assertInstanceOf(PDOStatement::class, $select->prepare());
-        $this->assertSame("SELECT `id` FROM `test` CROSS JOIN `users` `u` ON `u`.`id` = `test`.`user_id`;", $select->build());
-
-        $select->crossJoin('table2 AS t2', 't2.id', '=', 'test.user_id');
-        $expected = "SELECT `id` FROM `test` CROSS JOIN `users` `u` ON `u`.`id` = `test`.`user_id` CROSS JOIN `table2` AS `t2` ON `t2`.`id` = `test`.`user_id`;";
-        $this->assertSame($expected, $select->build());
-
-        $select->leftJoin('table3 AS t3', 't3.id', '=', 'test.user_id');
-        $expected = "SELECT `id` FROM `test` CROSS JOIN `users` `u` ON `u`.`id` = `test`.`user_id` CROSS JOIN `table2` AS `t2` ON `t2`.`id` = `test`.`user_id` LEFT JOIN `table3` AS `t3` ON `t3`.`id` = `test`.`user_id`;";
-        $this->assertSame($expected, $select->build());
-    }
-
     /**
      * Test
      *