Oracle-如何从案例中返回多个记录

如何从“案例默认”返回多条记录

例如：

---

我试着通过一个，它返回1。但当我通过'four'时，它显示了错误，比如ORA-01427单行子查询返回多行。我如何解决这个问题？？？

您得到了ORA-01427错误，因为在else部分的select查询中返回了多行

以下查询将帮助您：

WITH t AS
     (SELECT 1 string FROM dual
     UNION
     SELECT 2 string FROM dual
     UNION
     SELECT 1234 string FROM dual
     )
SELECT * FROM t
where t.string in ( case 'one' when 'one' then 1 else (select 1234 from dual) end);

output
_____
1

WITH t AS
     (SELECT 1 string FROM dual
     UNION
     SELECT 2 string FROM dual
     UNION
     SELECT 1234 string FROM dual
     )
SELECT * FROM t
where t.string in ( case 'two' when 'one' then 1 else (select 1234 from dual) end);

output
------
1234

---

您可以这样尝试：

column1 in (CASE '@InputString'
                    WHEN 'One' THEN 1
                    WHEN 'Two' THEN 2
                    WHEN 'THREE' THEN 3                    
                   END)
OR (column1 in (SELECT NUM_BER FROM TABLE1 WHERE COLUMN2 LIKE '%@InputString%')
    and '@InputString' not in ('One', 'Two', 'THREE'));

---

您可以使用

解码

SQL> ed
Wrote file afiedt.buf

  1  with x as (
  2     select 'A' as string from dual union all
  3     select 'B' from dual union all
  4     select 'C' from dual union all
  5     select 'D' from dual
  6  )
  7  select     string , decode(string, 'A',1,'B',2,3) as string_out
  8* from       x
SQL> /

S STRING_OUT
- ----------
A          1
B          2
C          3
D          3

---

CASE语句中的每个WHEN子句只能返回一个值，不能返回一组值。下面@ABCade发布的解决方案是您的最佳选择。

SQL> ed
Wrote file afiedt.buf

  1  with x as (
  2     select 'A' as string from dual union all
  3     select 'B' from dual union all
  4     select 'C' from dual union all
  5     select 'D' from dual
  6  )
  7  select     string , decode(string, 'A',1,'B',2,3) as string_out
  8* from       x
SQL> /

S STRING_OUT
- ----------
A          1
B          2
C          3
D          3