如果行中的列具有相同的值，如何检查它？

Question

I'd like to check a column in a table if they have the same value.

ID    School_Name     Student    Status
1        Virginia        Alex         2
2        Virginia        John         2
3       Wonderbow        Devi         1
4     San Antonio       Lucas         1
5     San Antonio       Larsa         2

How to check the column status if the value is 2 for each School_Name. The output is some thing like this:

ID       School_Name    school_stat
 1          Virginia      TRUE      
 2         Wonderbow     FALSE
 3       San Antonio     FALSE

So, if all student in each school name has the status of 2, the result is TRUE.

Current Query:

SELECT *,SUM(case when status > 1 then TRUE else FALSE end) as school_stat from t_school

The query giving wrong output though.

Answer 1

You can use conditional aggregation:

SELECT
    School_Name,
    IF(COUNT(1) = COUNT(IF(Status = 2, 1, NULL)), 'TRUE', 'FALSE') school_stat
FROM t_school
GROUP BY School_Name

See demo in SQLFiddle, and if you want to do some aggregation things, non-aggregation column like id will make no sense in select.