---
tags: Laravel, left join, db
---
# Laravel left join攜帶多個條件的寫法

laravel框架自身封裝的leftJoin方法如下：

public function leftJoin($table, $first, $operator = null, $second = null)  
{  
    return $this->join($table, $first, $operator, $second, ‘left’);  
}

瀏覽下 \\vendor\\laravel\\framework\\src\\Illuminate\\Database\\Query\\Builder.php檔案，發現join方法可用實現自己想要的left join攜帶多引數。laravel自身的join方法如下：

public function join($table, $one, $operator = null, $two = null, $type = ‘inner’, $where = false)
{
    // If the first “column” of the join is really a Closure instance the developer
    // is trying to build a join with a complex “on” clause containing more than
    // one condition, so we’ll add the join and call a Closure with the query.
    if ($one instanceof Closure) {
        $join = new JoinClause($type, $table);

        call_user_func($one, $join);

        $this->joins[] = $join;

        $this->addBinding($join->bindings, ‘join’);
    }

    // If the column is simply a string, we can assume the join simply has a basic
    // “on” clause with a single condition. So we will just build the join with
    // this simple join clauses attached to it. There is not a join callback.
    else {
        $join = new JoinClause($type, $table);

        $this->joins[] = $join->on(
            $one, $operator, $two, ‘and’, $where
        );

        $this->addBinding($join->bindings, ‘join’);
    }

    return $this;
}

當攜帶多條件時，可以這樣寫：

->leftJoin('cert_group as cg',function($join){  
   $join->on('cg.id', '=', 'cgm.cg_id')  
        ->on('cg.cp_id', '=', 'cgm.cp_id');  
})

或

->join('app_b as b',function($join){
    $join->on('a.id','=','b.goodId')
         ->where('b.status','=','SUCCESS')
         ->where('b.type','=','UNLOCK');
}, null,null,'left')