ORACLE

Question

我有以下 SELECT 声明：

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 table：

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 语句不止一次遍历 table 来完成工作，但我试图一次遍历 table 1 行并更新每一行如果它满足其中一个条件 - 否则，我将覆盖我之前更新的内容。

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 table 被多次读取。您的 UPDATE 语句没有 WHERE 子句，因此无论 nsf_code 值如何，它都会更新 table 中的每一行。如果要更新行的子集，则需要包含 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 table 一次）

ORACLE - UPDATE each row conditionally (iterate table only once)

conditional

case

sql-update