Getting error: "Missing keyword" when using case in where clause

Question

SELECT *
  FROM corp_action_restriction car1
  LEFT OUTER JOIN investment_account inv
    ON CASE
       WHEN REGEXP_LIKE(REGEXP_SUBSTR(car1.restriction_value,
                                      '[^|]+',
                                      1,
                                      1),
                        '^[[:digit:]]*$') THEN
        TO_NUMBER(REGEXP_SUBSTR(car1.restriction_value, '[^|]+', 1, 1)) =
        inv.investment_account_id
       ELSE
        car1.restriction_value = TO_CHAR(inv.investment_account_id)
       END

我遇到了缺少关键字的错误。

谁能告诉我这个查询有什么问题？

ORA-00905: missing keyword
00905. 00000 - "missing keyword"
*Cause:
*Action:
Error at Line: 4 Column: 61

Answer 1

那就是

SELECT *
  FROM CORP_ACTION_RESTRICTION CAR1
       LEFT OUTER JOIN INVESTMENT_ACCOUNT INV
          ON INV.INVESTMENT_ACCOUNT_ID =
             CASE
                WHEN REGEXP_LIKE (REGEXP_SUBSTR (CAR1.RESTRICTION_VALUE,
                                                 '[^|]+',
                                                 1,
                                                 1),
                                  '^[[:digit:]]*$')
                THEN
                   TO_NUMBER (REGEXP_SUBSTR (CAR1.RESTRICTION_VALUE,
                                             '[^|]+',
                                             1,
                                             1))
                ELSE
                   CAR1.RESTRICTION_VALUE
             END;

换句话说，将 inv.investment_account_id 放入 ON 子句中，然后将其（使用 =）与 case 表达式的结果进行比较。

Answer 2

因为return_expr或else_expr不能是布尔表达式类型。而且REGEXP_SUBSTR()的第三个和第四个参数(1&1)是多余的。

确实不需要CASE..WHEN表达式，如果数据库版本是12cR2+，那么考虑使用

SELECT *
  FROM corp_action_restriction car1
  LEFT JOIN investment_account inv
    ON TO_NUMBER(
                 REGEXP_SUBSTR(
                               car1.restriction_value, 
                               '[^|]+'
                              )  
                 DEFAULT NULL ON CONVERSION ERROR
                ) = inv.investment_account_id

这样就不会因为转换而报错

Demo

Getting error: "Missing keyword" when using case in where clause

Getting error: "Missing keyword" when using case in where clause

sql

oracle

case