Question

我有以下SELECT语句：

SELECT COUNT(*) FROM EPS_PROPOSAL 
WHERE NSF_CODE = 14 OR
      NSF_CODE =  5 OR
      NSF_CODE =  3 OR
      NSF_CODE = 45 OR
      NSF_CODE = 11 OR
      NSF_CODE =  2 OR
      NSF_CODE =  7 OR
      NSF_CODE = 46 OR
      NSF_CODE = 37 OR
      NSF_CODE = 22 OR
      NSF_CODE = 40 OR
      NSF_CODE =  9 OR
      NSF_CODE = 47 OR
      NSF_CODE = 19 OR
      NSF_CODE = 13 OR
      NSF_CODE =  4 OR
      NSF_CODE = 48 OR
      NSF_CODE = 42 OR
      NSF_CODE = 49 OR
      NSF_CODE = 50 OR
      NSF_CODE = 31 OR
      NSF_CODE = 27 OR
      NSF_CODE = 10 OR
      NSF_CODE = 41 OR
      NSF_CODE = 39 OR
      NSF_CODE = 35 OR
      NSF_CODE = 21;

1   COUNT(*) = 902

现在，如果我尝试使用以下UPDATE语句遍历EPS_PROPOSAL表：

UPDATE EPS_PROPOSAL
SET NSF_CODE = (CASE WHEN NSF_CODE = 14 THEN 3
                     WHEN NSF_CODE =  5 THEN 4
                     WHEN NSF_CODE =  3 THEN 5
                     WHEN NSF_CODE = 45 THEN 7
                     WHEN NSF_CODE = 11 THEN 8
                     WHEN NSF_CODE =  2 THEN 9
                     WHEN NSF_CODE =  7 THEN 11
                     WHEN NSF_CODE = 46 THEN 12
                     WHEN NSF_CODE = 37 THEN 13
                     WHEN NSF_CODE = 22 THEN 14
                     WHEN NSF_CODE = 40 THEN 41
                     WHEN NSF_CODE =  9 THEN 19
                     WHEN NSF_CODE = 47 THEN 20
                     WHEN NSF_CODE = 19 THEN 21
                     WHEN NSF_CODE = 13 THEN 2
                     WHEN NSF_CODE =  4 THEN 22
                     WHEN NSF_CODE = 48 THEN 23
                     WHEN NSF_CODE = 42 THEN 24
                     WHEN NSF_CODE = 49 THEN 25
                     WHEN NSF_CODE = 50 THEN 27
                     WHEN NSF_CODE = 31 THEN 29
                     WHEN NSF_CODE = 27 THEN 31
                     WHEN NSF_CODE = 10 THEN 34
                     WHEN NSF_CODE = 41 THEN 35
                     WHEN NSF_CODE = 39 THEN 37
                     WHEN NSF_CODE = 35 THEN 38
                     WHEN NSF_CODE = 21 THEN 39 END);    

1,866 rows updated.

看来，我的UPDATE语句多次遍历表以完成工作，但是我试图一次遍历表1行，并在满足条件之一的情况下更新每一行-否则，我将覆盖以前更新的内容。

底线-我应该只看到902行已更新。

有什么建议吗？

Answer 1

问题似乎不是表已被读取多次。您的UPDATE语句没有WHERE子句，因此无论nsf_code的值如何，它都会更新表中的每一行。如果要更新行的子集，则需要包括一个WHERE子句

UPDATE eps_proposal
   SET nsf_code = (CASE ...)
 WHERE nsf_code IN (14,5,3,...,21)

ORACLE-有条件地更新每一行（仅迭代一次表）

1 个答案: