Question

我试图在嵌套情况下从abcdef表中检索值，但在SELECTS MENTIONED ----错误中出现“单行子查询返回多个行”错误。情况1：当colC值为NOT NULL且没有值（'LM'，'OP'，'QR'）时，当colD为NULL时，colD值介于'00'和'99'之间情况2：当colC值为NOT NULL且何时具有值（'LM'，'OP'，'QR'）时，当colD为NULL时返回该行，或者当colE为null时返回该行

如何重写此查询以获得正确的结果

Table abcdef
colfKEY | colA | colB | colC | colD | colE

Table maintable
colPKEY | colTemp

select 
a.colA , a.colB, a.colC,
CASE  
    WHEN a.colC IS NULL THEN ''    
    WHEN a.colC IS NOT NULL THEN 
       (CASE  
         WHEN  (a.colC NOT IN ('LM','OP','QR')) THEN
          (CASE WHEN (a.colD IS NULL) THEN 
            (SELECT T.colD FROM abcdef T where T.colD IS NULL)   ---- error here
          WHEN TT.colD IS NOT NULL THEN 
           (SELECT TT.colD from abcdef TT WHERE (TT.colD < '00') OR (TT.colD  > '99') )  ---- error here 
          END)

        WHEN (a.colC  IN ('LM','OP','QR')) THEN
       (CASE WHEN a.colD IS NULL THEN 
             (SELECT a.colD FROM abcdef a) ---- error here
         WHEN a.colE IS NULL THEN 
            (SELECT a.colE FROM abcdef a) ---- error here
        END )
        END)
END
from abcdef a where
a.colfKEY IN
(SELECT m.colPKEY FROM maintable m where 
m.colTemp= '999999');

Answer 1

不用子查询重写查询：

SELECT a.colA,
       a.colB,
       a.colC,
       CASE
         WHEN a.colC IS NULL THEN
          ''
         WHEN a.colC IS NOT NULL THEN
          (CASE
            WHEN (a.colC NOT IN ('LM', 'OP', 'QR')) THEN
             (CASE
               WHEN (a.colD IS NULL) THEN
                     a.colD
               WHEN a.colD IS NOT NULL AND ((a.colD < '00') OR (a.colD > '99')) THEN
                    a.colD
             END)

            WHEN (a.colC IN ('LM', 'OP', 'QR')) THEN
             (CASE
               WHEN a.colD IS NULL THEN
                    a.colD 
               WHEN a.colE IS NULL THEN
                    a.colE 
             END)
          END)
       END
  FROM abcdef a
  JOIN maintable m 
    ON a.colfKEY = m.colPKEY 
 WHERE m.colTemp = '999999';

带有SELECT的Oracle SQL嵌套案例返回单行子查询返回多个行

1 个答案: