sql - 在子查询和同一张表中更新

Question

我想更新多行数据，但出现错误。

下面是表信息和查询语句。

我的表

ltiNum  ltiCd   updateDate  ClosedOrNot

1   A   2020-07-01  
2   B   2020-07-01  
3   C   2020-07-01  
4   D   2020-07-01  
5   E   2020-07-01  
1   A   2020-08-01  
3   C   2020-08-01  
4   D   2020-08-01  
5   E   2020-08-01  
6   F   2020-08-01  

SQL

update myTable 
set closedOrNot = 
        (case when (SELECT CONCAT(ltiNum,ltiCd) FROM myTable where updateDate Like '2020-08%'
                    and CONCAT(ltiNum,ltiCd) in (SELECT CONCAT(ltiNum,ltiCd) FROM myTable WHERE updateDate Like '2020-07%'       
        )) then 'existing'
        when (SELECT CONCAT(ltiNum,ltiCd) FROM myTable where updateDate Like '2020-08%'
                    and CONCAT(ltiNum,ltiCd) not in (SELECT CONCAT(ltiNum,ltiCd) FROM myTable WHERE updateDate Like '2020-07%'
        )) then 'New'        
         when (SELECT CONCAT(ltiNum,ltiCd) FROM myTable where updateDate Like '2020-07%'
                    and CONCAT(ltiNum,ltiCd) not in (SELECT CONCAT(ltiNum,ltiCd) FROM myTable WHERE updateDate Like '2020-08%'
        )) then 'Closed'
    end);

错误代码：

mysql 错误代码 1093: You can't specify target table for 'myTable' 在 FROM 子句中更新

问题出在哪里？

我想看后续图片

请帮忙~！

Answer 1

您必须将 mytable 封装在 SELECT 中

update myTable 
set closedOrNot = 
        (case when (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 where updateDate Like '2020-08%'
                    and CONCAT(ltiNum,ltiCd) in (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 WHERE updateDate Like '2020-07%'       
        )) then 'existing'
        when (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 where updateDate Like '2020-08%'
                    and CONCAT(ltiNum,ltiCd) not in (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 WHERE updateDate Like '2020-07%'
        )) then 'New'        
         when (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 where updateDate Like '2020-07%'
                    and CONCAT(ltiNum,ltiCd) not in (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 WHERE updateDate Like '2020-08%'
        )) then 'Closed'
    end);

所以mysql认为，这是另一个表，但你基本上是在改变所有的行，因为你没有使用WHERE子句，所以可能会发生更远的路，结果可能会改变

基本上你告诉你的一切都是正确的，但你的查询还有另一个问题

CREATE TABLE myTable (
  `ltiNum` INTEGER,
  `ltiCd` VARCHAR(1),
  `updateDate` VARCHAR(10),
  `closedOrNot` VARCHAR(8)
);

INSERT INTO myTable
  (`ltiNum`, `ltiCd`, `updateDate`, `closedOrNot`)
VALUES
  ('1', 'A', '2020-07-01', 'NULL'),
  ('2', 'B', '2020-07-01', 'Closed'),
  ('3', '0', '2020-07-01', 'NULL'),
  ('4', 'D', '2020-07-01', 'NULL'),
  ('5', 'E', '2020-07-01', 'NULL'),
  ('1', 'A', '2020-08-01', 'existing'),
  ('3', '0', '2020-08-01', 'existing'),
  ('4', 'D', '2020-08-01', 'existing'),
  ('5', 'E', '2020-08-01', 'existing'),
  ('6', 'F', '2020-08-01', 'New');

update myTable 
set closedOrNot = 
        (case when (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 where updateDate Like '2020-08%'
                    and CONCAT(ltiNum,ltiCd) in (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 WHERE updateDate Like '2020-07%'       
        )) then 'existing'
        when (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 where updateDate Like '2020-08%'
                    and CONCAT(ltiNum,ltiCd) not in (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 WHERE updateDate Like '2020-07%'
        )) then 'New'        
         when (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 where updateDate Like '2020-07%'
                    and CONCAT(ltiNum,ltiCd) not in (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 WHERE updateDate Like '2020-08%'
        )) then 'Closed'
    end);

子查询返回超过 1 行

 SELECT CONCAT(ltiNum,ltiCd) 
 FROM (SELECT * FROM myTable) t1 
 where updateDate Like '2020-08%'
                    and CONCAT(ltiNum,ltiCd) in (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 WHERE updateDate Like '2020-07%' )      

| CONCAT(ltiNum,ltiCd) | | :-------------------- | | 1A | | 30 | | 4D | | 5E |

SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 where updateDate Like '2020-08%'
                    and CONCAT(ltiNum,ltiCd) not in (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 WHERE updateDate Like '2020-07%'
        )

| CONCAT(ltiNum,ltiCd) | | :-------------------- | | 6F |

SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 where updateDate Like '2020-07%'
                    and CONCAT(ltiNum,ltiCd) not in (SELECT CONCAT(ltiNum,ltiCd) FROM (SELECT * FROM myTable) t1 WHERE updateDate Like '2020-08%'
        )

| CONCAT(ltiNum,ltiCd) | | :-------------------- | | 2B |

db小提琴here

如您所见，第一个 CASE 返回 4 个结果，因此您的构造不起作用-