Weird:无法为FROM子句中更新指定目标表

I don't understand why my query runs fine in phpMyAdmin and in my php script it gives me the message: can't specify target table for update in FROM clause!!!

我不明白为什么我的查询在phpMyAdmin中运行得很好，在php脚本中，它给了我这样的信息:不能为FROM子句中的update指定目标表!!

update tableA set 
Field1 = round(round((select (select br.FieldA from tableB br where tableA.id=br.id and tableA.id2=br.id2) as x),4) - round(tableA.FieldA,4),4)

3 个解决方案

#1

That is correct. You cannot select in the nested query the same table you're updating now.

这是正确的。不能在嵌套查询中选择正在更新的同一表。

The better solution will be to use joins in your update. http://dev.mysql.com/doc/refman/5.5/en/update.html

更好的解决方案是在更新中使用连接。http://dev.mysql.com/doc/refman/5.5/en/update.html

#2

This should work with multi-table update:

这应该适用于多表更新:

UPDATE tableA, tableB
SET tableA.Field1 = round(round(tableB.FieldA, 4) - round(tableA.FieldA,4), 4)
WHERE tableA.id=tableB.id AND tableA.id2=tableB.id2;

Search for join in http://dev.mysql.com/doc/refman/5.0/en/update.html

在http://dev.mysql.com/doc/refman/5.0/en/update.html中搜索join

#3

you can do it using multiple copies of the same table like this:

您可以使用同一表的多个副本来完成，如下所示:

UPDATE tablename, tablename b 
SET tablename.col1 = val 
WHERE tablename.col1 = b.col1 AND b.col2 IN (val1,val2,val3);

The val in the above query can also be a variable like b.col2.

上述查询中的val还可以是b.col2之类的变量。

#1