将完全相同列上的两个查询连接到一个结果表中

Question

INSERT INTO COLOR
SELECT 'COLOR', 'RED'
UNION
SELECT 'config', 'RED'
UNION
SELECT 'CONFIG_VALUE', 'RED'
UNION
SELECT 'XYZ', 'BLUE'
UNION
SELECT 'TEST', 'BLUE'
UNION
SELECT 'COLOR', 'BLUE'
UNION
SELECT 'COLOR', 'RED'
UNION
SELECT 'COLOR', 'BLUE'
UNION
SELECT 'COLOR', 'RED'

I would like to run two queries on the same column, to get a result table that has a count of how many blue and red items there are - blue as the title for one column, and red being the title of the second column.

I have the two separate queries returning the count for each one, but when I join these with a union it turns out strange.

Is this possible? Thanks.

Answer 1

You can use conditional aggregation:

select sum(case when color = 'BLUE' then 1 else 0 end) as blue,
       sum(case when color = 'RED' then 1 else 0 end) as red
from t;