Question

我的表格中包含book，startyear，endyear和author等列。

我需要根据以下条件同时更新startyear和endyear列，

STARTYEAR = ENDYEAR where STARTYEAR=0 and ENDYEAR != 0 
also
ENDYEAR = STARTYEAR  where ENDYEAR =0 and STARTYEAR != 0

可以使用

UPDATE Table SET STARTYEAR = ENDYEAR WHERE STARTYEAR=0 AND ENDYEAR<>0; 
UPDATE Table SET ENDYEAR = STARTYEAR  WHERE ENDYEAR =0 AND STARTYEAR<>0;

如何在一个查询中编写这两个查询？

Answer 1

update table
set 
startYear = case when startyear = 0 and endyear<>0 then endyear else startYear end,
endYear = case when endyear = 0 and startyear <> 0 then startyear else endYear end
where startyear = 0 or endyear = 0;

Answer 2

另一种方式是：

UPDATE Table 
SET STARTYEAR = STARTYEAR + ENDYEAR
  , ENDYEAR   = STARTYEAR + ENDYEAR
WHERE STARTYEAR = 0 AND ENDYEAR <> 0
   OR ENDYEAR = 0 AND STARTYEAR <> 0 ;

但我真的没有看到任何理由这样做。您可以在事务中使用2语句。它甚至可能比任何复杂的单一陈述更有效。

Answer 3

您可以使用或更新机器人字段，除非您有触发器阻止您在startyear = endyear = 0;

的情况下执行此操作

UPDATE Table SET STARTYEAR = STARTYEAR+ ENDYEAR, ENDYEAR = STARTYEAR+ENDYEAR WHERE STARTYEAR=0 OR ENDYEAR=0

Answer 4

您无法在一个语句中更新多个表，但是，您可以使用事务来确保将两个UPDATE语句视为一个。您也可以批量处理它们以避免往返。

BEGIN TRANSACTION

UPDATE Table SET STARTYEAR = ENDYEAR WHERE STARTYEAR=0 AND ENDYEAR<>0; 

UPDATE Table SET ENDYEAR = STARTYEAR  WHERE ENDYEAR =0 AND STARTYEAR<>0;

COMMIT

但在您的情况下，您也可以使用this post中的答案。

Answer 5

这应该有效，

update test
   set startyear = (case when startyear = 0 AND endyear <> 0 then endyear else startyear end),
       endyear   = (case when endyear = 0 AND startyear <> 0 then startyear else endyear end);

在同一个表中的两个条件下更新表

5 个答案: