MYSQL 根据数据内容单独计数生产列

Question

我想用一句SQL语句，让如下图所示的列1，根据内容生成内容计数的列。
我的写法是
SELECT count（列1=“A”）as A, count（列1=“B1”）as B1, count（列1=“B”）as B, count（列1=“C1”）as C1 FROM 表
但是这样不对，出来的计数都是1 .
我又试过
SELECT count（列1）=“A” as A, count（列1）=“B1” as B1, count（列1）=“B” as B, count（列1）=“C1” as C1 FROM 表
也不对，出来的计数都是0 ，请问我应该怎么写

Answer 1

查到了，利用Case When Then Else End 多条件判断可以实现

count(case defectRank when "A" then 1 else null end) as A,count(case defectRank when "B1" then 1 else null end) as B1,count(case defectRank when "B" then 1 else null end) as B,count(case defectRank when "C1" then 1 else null end) as C1