mysql - SQL case statement - Multiple conditions

Question

I am writing a case statement where I need to check columns and assign a value . But what if a row qualifies for multiple cases ? For example in following table I want assign a bucket when COLA and/or COLB is null ; so in first case both are NULL , so how will I tell SQL case statement to assign "Both are NULL " when COLA and COLB are null. I can easily assign when COLA or COLB is null . At my work I am checking 8 columns , so I need to find every combination and right case for that ? There has to be an easy way .

**RowNumber     COLA                  COLB                Case**
1                   Null                  Null               **Both are NULL** 
2                   Null                  B                        A is null
3                   A                 Null                 B is null 
4                   AA                BB                   NULL
5                   CC                Null                 B is null 

Answer 1

鉴于您有 8 列，您可能需要执行以下操作：

WITH t AS (
    SELECT
        CASE WHEN (colA IS NULL AND colB IS NULL AND colC IS NULL AND colD IS NULL AND 
                   colE IS NULL AND colF IS NULL AND colG IS NULL AND colH IS NULL) THEN 'ALL' ELSE '' END [ALL],
        CASE WHEN colA IS NULL THEN 'A' ELSE '' END [A],
        CASE WHEN colB IS NULL THEN 'B' ELSE '' END [B],
        CASE WHEN colC IS NULL THEN 'C' ELSE '' END [C],
        CASE WHEN colD IS NULL THEN 'D' ELSE '' END [D],
        CASE WHEN colE IS NULL THEN 'E' ELSE '' END [E],
        CASE WHEN colF IS NULL THEN 'F' ELSE '' END [F],
        CASE WHEN colG IS NULL THEN 'G' ELSE '' END [G],
        CASE WHEN colH IS NULL THEN 'H' ELSE '' END [H] 
        FROM
            <TABLENAME>)                                

SELECT 
    CASE WHEN [ALL] = 'ALL' THEN 'ALL are NULL'
    ELSE [ALL] + ',' + A + ',' + B + ',' + C + ',' + D + ',' 
               + E + ',' + F + ',' + G + ',' + H + ' are NULL' 
END
FROM T

在最终的 select 语句中，您可以进行进一步的更改以根据需要显示结果。