Question

我看到使用CASE columnX WHEN NULL

为Oracle做了很多查询

如何设计查询

CASE columnX WHEN NOT NULL？

SQL开发人员在查询上抛出错误，以便如何使用CASE进行条件查询... WHEN ...？

WITH dates_list AS
  (SELECT TO_DATE('02-19-2018','MM-dd-yyyy') + ROWNUM - 1 AS DAY,
    rownum                                                AS row_num
  FROM dual
    CONNECT BY LEVEL <= (TO_DATE('03-29-2018','MM-dd-yyyy') - TO_DATE('02-19-2018','MM-dd-yyyy')+1)
  )
SELECT dates1.day, dates2.*, count(case dates2.day when null then 1 else 0 end) 
              over (partition by dates2.day order by dates1.day) as cnt
FROM dates_list dates1
LEFT JOIN
  (SELECT *
  FROM dates_list
  WHERE TO_CHAR(DAY,'D') NOT IN (7,1)
  ) dates2 ON dates1.day = dates2.day
ORDER BY dates1.day;

当我将when null更改为when not null

时，

以上查询会出错

Answer 1

你不能以这种方式使用CASE句子和NULL值，因为columnX永远不会等于＆＃34;为NULL。您应该使用：

CASE WHEN columnX IS NULL THEN

或

CASE WHEN columnX IS NOT NULL THEN

Oracle的情况是否为null？

1 个答案: