MySql更新和替换表字段相对于其他字段

Question

I want to replace a table field based on other table field condition,

How it now

Table : question 
---------------------------
Category  | Subcat |
--------------------------
11           0
11           0
11           0
11           0
11           0
12           1
12           1
12           1
12           1
----------------------

I want to replace 0 with 5 where main category is 11

I have tried below code

UPDATE `question` SET `subcat` = REPLACE(`subcat`, '0', '5') 

This replace all 0 present in any main category not in based on particular

Answer 1

You need a proper where condition for filter the rows you really need to change

UPDATE question 
SET subcat = 5 
where category =11 
and subcat  = 0