sql - 在子查询和同一个表中更新

Question

我想更新多行数据，但发生错误。

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：您无法在 FROM 子句中为“myTable”更新指定目标表

问题出在哪儿？

我想看后续图片

请帮忙~！

Answer 1

您必须用 SELECT 封装 mytable

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，但你基本上改变了所有的行，因为你没有使用WHERE子句，所以可能会发生在更远的路上，结果可能会改变

基本上一切都是正确的 o 告诉你的但你的查询有另一个问题

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);

\n子查询返回超过 1 行\n

 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%' )

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

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%' )

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

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%' )

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

db<> 在这里摆弄

如您所见，第一个 CASE 返回 4 个结果，因此您的构建不起作用-