MySQL：The used SELECT statements have a different number of columns

梦里梦外; 2023-05-22 06:45 6阅读 0赞

**执行SQL报错：The used SELECT statements have a different number of columns**

> 以上翻译：使用的SELECT语句具有不同数量的列

原因：我们在 SQL 语句中使用了 UNION 连接两张表时，查询字段数量不一致导致

**\# 效果展示**：  
![效果图][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDY1Nzc2_size_16_color_FFFFFF_t_70]  
我们需要将数据展示如上图所示

**\# 错误案例**：

SELECT
    	a.quantity AS in_quantity,
    	a.price AS in_price,
    	(a.quantity * a.price) AS in_amount,
    	0 AS out_quantity,
    	0 AS out_price,
    	0 AS out_amount 
    FROM
    	store_in_detail a 
    WHERE
    	a.sku_id = 1345 
    UNION ALL
    SELECT
    	b.quantity AS out_quantity,
    	b.price AS out_price,
    	(b.quantity * b.price) AS out_amount 
    FROM
    	store_out_detail b 
    WHERE
    	b.sku_id = 1345

我们通过入库表 连接 出库表，得出商品 id = 1345 的出入库情况

执行SQL报错：The used SELECT statements have a different number of columns (使用的SELECT语句具有不同数量的列)

**\# 原因分析**：

我们在查询入库单，查询了四个字段：入库数量，入库单价，入库金额，出库数量（默认0），出库单价（默认0），出库金额（默认0）  
而查询出库单，只查询了两个字段：出库数量，出库单价，出库金额

两次查询的字段数量不一致，导致 SQL 异常

**\# 正确实例**：

SELECT
    	a.quantity AS in_quantity,
    	a.price AS in_price,
    	(a.quantity * a.price) AS in_amount,
    	0 AS out_quantity,
    	0 AS out_price,
    	0 AS out_amount 
    FROM
    	store_in_detail a 
    WHERE
    	a.sku_id = 1345 
    UNION ALL
    SELECT
    	0 AS in_quantity,
    	0 AS in_price,
    	0 AS in_amount,
    	b.quantity AS out_quantity,
    	b.price AS out_price,
    	(b.quantity * b.price) AS out_amount  
    FROM
    	store_out_detail b 
    WHERE
    	b.sku_id = 1345

SQL 执行成功

如您在阅读中发现不足，欢迎留言！！！

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwMDY1Nzc2_size_16_color_FFFFFF_t_70]: /images/20230521/62de19427c7a450aa52515978651106c.png