多个COUNT()用于一个查询中的多个条件(MySQL)

Question

我有这些疑问:

SELECT COUNT(*) FROM t_table WHERE color = 'YELLOW';
SELECT COUNT(*) FROM t_table WHERE color = 'BLUE';
SELECT COUNT(*) FROM t_table WHERE color = 'RED';

有没有办法在一个查询中获得这些结果？

Answer 1

SELECT color, COUNT(*) FROM t_table GROUP BY color

Answer 2

如果您希望结果在一行中,您可以使用:

SELECT
    SUM(IF(color = 'YELLOW', 1, 0)) AS YELLOW,
    SUM(IF(color = 'BLUE', 1, 0)) AS BLUE,
    SUM(IF(color = 'RED', 1, 0)) AS RED
FROM t_table

工作实例

Answer 3

SELECT 'yellow' as color ,COUNT(*) FROM t_table WHERE color = 'YELLOW'
union
SELECT 'blue' , COUNT(*) FROM t_table WHERE color = 'BLUE'
union
SELECT 'red',COUNT(*) FROM t_table WHERE color = 'RED';

要么

select color, count(*) from table where color in ('red', 'blue', 'yellow') group by 1