How to Solve MySQL Error 1093: 'You can't specify target table for update in FROM clause'?

MySQL Error 1093: Update query limit

Question:

When trying to update the pers table using a subquery, I get the error "You can't specify target table for update in FROM clause" (Error 1093).

Query:

UPDATE pers P
SET P.gehalt = P.gehalt * 1.05
WHERE (P.chefID IS NOT NULL
OR gehalt <p><strong>原因：</strong></p><p>MySQL 不允许在子查询中引用正在更新的同一表。</p><p><strong>解决方案：</strong></p><p>要解决此问题，请将外部表引用（pers）在子查询中用嵌套子查询括起来：</p>
```sql
UPDATE pers P
SET P.gehalt = P.gehalt * 1.05
WHERE (P.chefID IS NOT NULL
OR gehalt <p><strong>说明：</strong></p><p>通过使用 `SELECT * FROM pers` 创建嵌套子查询，我们隐式地创建了一个临时表，可以在子查询中引用它，而不会违反 MySQL 的限制。这允许我们使用所需的条件更新 `pers` 表。</p>

Improved solution (clearer example):

To illustrate the solution more clearly, a JOIN statement can be used instead of a subquery:

UPDATE pers p
INNER JOIN (SELECT chefID, gehalt FROM pers) AS subquery ON p.chefID = subquery.chefID AND p.gehalt = subquery.gehalt
SET p.gehalt = p.gehalt * 1.05
WHERE p.chefID IS NOT NULL OR p.gehalt < ...;

This method avoids directly referencing the pers table in the subquery, thus bypassing MySQL limitations. subquery Acts as a temporary table, allowing safe update operations. Note that you need to supplement the WHERE part based on the actual ... condition.

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