在同一个查询中统计同一个列的不同值的数量
select sum(if(color='blue',1,0)) as blue,sum(if(color='red',1,0)) as red from ys;
select count(color='blue' or null) as blue,count(color='red' or null) as red from ys;
select sum(if(color='blue',1,0)) as blue,sum(if(color='red',1,0)) as red from ys;
select count(color='blue' or null) as blue,count(color='red' or null) as red from ys;