简化并更正以下查询

Question

请问我该如何修复并可能简化这个 SQL 查询？

SELECT * FROM table WHERE
   M IN (NULL,1) AND T IN (NULL,1) AND J IN (NULL,1) AND B IN (NULL,1)
   AND (ISNULL(M,0)+ISNULL(T,0)+ISNULL(J,0)+ISNULL(B,0))<4
   ORDER BY (ISNULL(M,0)+ISNULL(T,0)+ISNULL(J,0)+ISNULL(B,0)) DESC

table 包含 4 列 (M,T,J,B)，只有 3 个可能的值 NULL, 0, 1。

一线过滤器仅获取包含 NULL 或 1.
第二行加法得到M+J+T+B的总和，只过滤if <4.
三线ORDER BY同Total,M+J+T+B.

错误#1582 - Incorrect parameter count in the call to native function 'ISNULL'

MySQL 等同于 ISNULL 是 IFNULL... answered here

Answer 1

空值在 SQL 中表现得很奇怪。任何与 null 的比较测试将导致 FALSE，因此如果您在 where 子句中使用短语 Null=Null，则不会检索到任何内容，因为结果始终为 false。我会重写你的第二行，改用 IsNull 函数，

IsNull(M,1)*IsNull(T,1)*IsNull(J,1)*IsNull(B,1)>0

Answer 2

select * from (
    select *, coalesce(M,0) M2, coalesce(T,0) T2, coalesce(J,0) J2, coalesce(B,0) B2
    from table
    where 
     (M is null or M=1) and
     (T is null or T=1) and
     (J is null or J=1) and
     (B is null or B=1) 
)x
where M2+T2+J2+B2 < 4
order by M2+T2+J2+B2 desc

Answer 3

Select 
 t.*,
 coalesce(M,0) + coalesce(T,0) + coalesce(J,0) + coalesce(B,0) as calc
from table t
where 
 coalesce(M,0) in (0,1) and
 coalesce(T,0) in (0,1) and
 coalesce(J,0) in (0,1) and
 coalesce(B,0) in (0,1) and
 calc < 4
order by calc desc

简化并更正以下查询

Simplify and correct following query

mysql

simplify