You can't specify target table for update in FROM clause

Question

I have a simple mysql table:

CREATE TABLE IF NOT EXISTS `pers` (
  `persID` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(35) NOT NULL,
  `gehalt` int(11         


        

Answer 1

Other workarounds include using SELECT DISTINCT or LIMIT in the subquery, although these are not as explicit in their effect on materialization. this worked for me

as mentioned in MySql Doc

Answer 2

The problem is that MySQL, for whatever inane reason, doesn't allow you to write queries like this:

UPDATE myTable
SET myTable.A =
(
    SELECT B
    FROM myTable
    INNER JOIN ...
)

That is, if you're doing an UPDATE/INSERT/DELETE on a table, you can't reference that table in an inner query (you can however reference a field from that outer table...)

---

The solution is to replace the instance of myTable in the sub-query with (SELECT * FROM myTable), like this

UPDATE myTable
SET myTable.A =
(
    SELECT B
    FROM (SELECT * FROM myTable) AS something
    INNER JOIN ...
)

This apparently causes the necessary fields to be implicitly copied into a temporary table, so it's allowed.

I found this solution here. A note from that article:

You don’t want to just SELECT * FROM table in the subquery in real life; I just wanted to keep the examples simple. In reality, you should only be selecting the columns you need in that innermost query, and adding a good WHERE clause to limit the results, too.

Answer 3

MySQL doesn't allow selecting from a table and update in the same table at the same time. But there is always a workaround :)

This doesn't work >>>>

UPDATE table1 SET col1 = (SELECT MAX(col1) from table1) WHERE col1 IS NULL;

But this works >>>>

UPDATE table1 SET col1 = (SELECT MAX(col1) FROM (SELECT * FROM table1) AS table1_new) WHERE col1 IS NULL;

Answer 4

You can make this in three steps:

CREATE TABLE test2 AS
SELECT PersId 
FROM pers p
WHERE (
  chefID IS NOT NULL 
  OR gehalt < (
    SELECT MAX (
      gehalt * 1.05
    )
    FROM pers MA
    WHERE MA.chefID = p.chefID
  )
)

...

UPDATE pers P
SET P.gehalt = P.gehalt * 1.05
WHERE PersId
IN (
  SELECT PersId
  FROM test2
)
DROP TABLE test2;

or

UPDATE Pers P, (
  SELECT PersId
  FROM pers p
  WHERE (
   chefID IS NOT NULL 
   OR gehalt < (
     SELECT MAX (
       gehalt * 1.05
     )
     FROM pers MA
     WHERE MA.chefID = p.chefID
   )
 )
) t
SET P.gehalt = P.gehalt * 1.05
WHERE p.PersId = t.PersId

Answer 5

In Mysql, you can not update one table by subquery the same table.

You can separate the query in two parts, or do

 UPDATE TABLE_A AS A
 INNER JOIN TABLE_A AS B ON A.field1 = B.field1
 SET field2 = ?