Question

我有两个表ECRDTL_del和ECRDTL_edit，我想只显示ECRDTL_del中不在ECRDTL_edit中的记录。我曾尝试使用MYSQL左连接，但无法获得所需的结果。这是我目前的查询字符串：

SELECT a.*
FROM ECRDTL_del AS a
    LEFT JOIN ECRDTL_edit AS b ON b.Ecrno = a.Ecrno
WHERE b.Cylno <> a.Cylno

数据示例表和下面提到的这两个表中的预期结果：

ECRDTL_del：

Ecrno  Cylno
9090   8881
9090   8882
9090   8883
9090   8884

ECRDTL_edit：

Ecrno  Cylno
9090   8881
9090   8885
9090   8886
9090   8884

LEFT加入后预期的结果：

Ecrno  Cylno
9090   8882
9090   8883

Answer 1

从你的问题：

“......我想只显示ECRDTL_del中不在ECRDTL_edit中的记录。”

你很近，你只需要检查一下b.Ecrno IS NULL。

SELECT a.* 
FROM   ECRDTL_del AS a 
       LEFT JOIN ECRDTL_edit AS b 
          ON a.Ecrno = b.Ecrno AND 
             a.Cylno = b.Cylno
WHERE  b.Ecrno IS NULL

SQLFiddle Demo

输出

╔═══════╦═══════╗
║ ECRNO ║ CYLNO ║
╠═══════╬═══════╣
║  9090 ║  8882 ║
║  9090 ║  8883 ║
╚═══════╩═══════╝

Answer 2

我通常会将EXISTS用于此类事情：

SELECT *
FROM ECRDTL_del as a
WHERE NOT EXISTS(
    SELECT *
    FROM ECRDTL_edit as b
    WHERE b.Ecrno = a.Ecrno
    AND b.Cylno = a.Cylno
)

找到匹配记录的那一刻，它就会停止，而IN之类的东西会继续搜索匹配的记录。

Answer 3

select * from ECRDTL_del where Cylno not in (select Cylno from ECRDTL_edit)

LEFT JOIN显示不在Right表中的记录

3 个答案: