mysql - MYSQL 中 CASE 内 CASE 的 SUM/COUNT

Question

表产品中有以下列:

a  |  b  | cat
--------------
2  |  4  |  1
3  |  1  |  1
4  |  4  |  1
2  |  1  |  1
3  |  2  |  1
5  |  3  |  1
8  |  7  |  2
5  |  3  |  2


$sql = "SELECT 
        SUM(CASE 
            WHEN
            cat = 1
            AND
            a > b  
            THEN 1 else 0 end) as prdplus
        FROM product
       ";

in above query i am getting value for sum or count of a greater then b

这是 3>1 , 2>1 , 3>2 , 5>3

因此上述查询的输出将是:4

prdplus
-------
4

what i need is count value have only +1 in above count of 4

这就是上面的查询，现在我需要 +1 值计数

3-1 = 2
2-1 = 1  // just explanation purpose , output i need in -> plus1 
3-2 = 1  // just explanation purpose , output i need in  -> plus1
5-3 = 2

因此对于上述查询，我​​只需要 +1 计数，即 2

我不知道如何在包含上述查询的情况下编写案例，因为我需要两个计数都显示在我的表格中，如下所示

最终输出:

 prdplus | plus1 
----------------
  4      |  2

Answer 1

SELECT SUM(CASE WHEN a > b  
                THEN 1 
                else 0 
           end) as prdplus,
       SUM(CASE WHEN a - b = 1  
                THEN 1 
                else 0 
           end) as prdplus1
FROM product