Question

我想在select语句中使用这个子查询

select category from `categories` WHERE id = `products`.`category_id`

这是我方法的select语句部分

$query = $this->select(
   DB::raw('COUNT(DISTINCT(`order_details`.`product_id`)) as productCount'), 'products.category_id',
   DB::raw('('.DB::select('select category from `categories` WHERE id = `products`.`category_id` ').') AS category ')
);

错误：

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'products.category_id' in 'where clause' (SQL: select category from `categories` WHERE id = `products`.`category_id` )

我讨厌使用直接选择语句。因为我改变数据库是不好的。

尽管使用直接选择语句但它无效。我怎么能这样做？

Answer 1

只需更新以下声明

即可

DB::raw('('.DB::select('select category from `categories` WHERE id = `products`.`category_id` ').') AS category ')

进入

DB::raw('(select category from `categories` WHERE id = `products`.`category_id`) AS category')

此处的错误是针对未知列products.category_id，您需要检查表中是否有category_id

Answer 2

请按照以下示例查看其中一个子查询：

$result = static::select('id')
        ->where( 'id', '!=', $currentLevelId)
        ->where('level', '>', DB::raw("(SELECT level FROM " . $this->table . " WHERE id='".$currentLevelId."')") )
        ->orderBy('level')->first();

结果查询：

SELECT * FROM `approval_levels` WHERE `id` != 2 AND `level` > (SELECT LEVEL
 FROM approval_levels WHERE id='2') ORDER BY `level` ASC LIMIT 1

希望它有所帮助！

Laravel 5.2中Select语句中的子查询

2 个答案: