WHERE 子句中的嵌套 CASE 语句

Question

我正在尝试使用 NESTED CASE 语句（下粗体），根据第一个 CASE 语句，我需要验证内部 where 子句，否则验证其他内部 where 子句。使用嵌套 CASE When 语句时是否采用右下方方法？

SELECT COUNT(*)
FROM   <list of table>
WHERE  <list of conditions > 
AND    CASE  WHEN cond1 <> 1 or cond2 <>2 or cond3 <> 3
             THEN 
                WHEN ( col1,col2,col3) NOT IN (SELECT col1,col2,col3
                                               FROM   table 1,table 2
                                               WHERE  <condition1> )
                ELSE ( col1,col2,col3,col4) NOT IN (SELECT col1,col2,col3,col4
                                                    FROM   table 1,table 2
                                                    WHERE  <condition2> )
             END

Answer 1

使用AND和OR:

SELECT COUNT(*)
FROM   <list of table>
WHERE  <list of conditions > 
AND    (  (   ( cond1 <> 1 OR cond2 <> 2 OR cond3 <> 3 )
          AND (col1,col2,col3) NOT IN (SELECT col1,col2,col3
                                       FROM   table1
                                              INNER JOIN table2
                                              ON (<condition>)
                                       WHERE  <condition1>)
          )
       OR (   NOT ( cond1 <> 1 OR cond2 <> 2 OR cond3 <> 3 )
          AND (col1,col2,col3,col4) NOT IN (SELECT col1,col2,col3,col4
                                            FROM   table1
                                                   INNER JOIN table2
                                                   ON (<condition2>)
                                            WHERE  <condition2> )
          )
       )

注意：不要使用旧式逗号连接，使用现代 ANSI 连接语法。

WHERE 子句中的嵌套 CASE 语句

Nested CASE statement in the WHERE clause

sql

oracle

switch-statement