Case when then (SQL)

 

Case has two formats. Branch Structure CASE statement and condition judgment case statement.

 

Branch Structure CASE statement, similar to switch

Select
(
Case user_name
When 'zhang san' then 'zhangsan'
When 'lily' then 'lisi'
When 'wang Wu 1 'then' wangwu'
Else 'cannot find the corresponding 'end
) As
From ctl_user

 

Condition judgment case, similar to If else

Select
(
Case
When user_code> 0 and user_code <100 then 'less than one hundred'
When user_code> 100 and user_code <1000 then 'less than one thousand'
When user_code> 1000 and user_code <2000 then 'less than 10 thousand'
Else 'out of range' End
) As
From ctl_user

 

Note the writing of the two.

There is another issue to be aware,Branch Structure CASE statementOnly the first qualified value is returned, and the remaining case is automatically ignored.