Question

我有一个具有可空字段的临时表（在SQL SERVER 2008中）我想将登台表中的记录插入或更新到主表在此期间，我想要进行比较

Update main
set main.field1 = (
if(staging.field1 isnull)
    then ---- 
else if(staging.field2 isnull)
    then ---- 
else
    then
)

如何在插入和更新语句中嵌入上述条件？

Answer 1

（某种）等价物是使用CASE表达式：

UPDATE main
SET main.field1 =
  CASE
    WHEN staging.field1 IS NULL
      THEN --
    WHEN staging.field2 IS NULL
      THEN --
    ELSE --
  END;

Answer 2

MERGE INTO main
   USING staging
      ON main.id = staging.id
WHEN MATCHED THEN
   UPDATE
      SET field1 = COALESCE( staging.field1 , main.field1 ), 
      SET field2 = COALESCE( staging.field2 , main.field2 ), 
      ... ;

在insert和update语句中使用if / else

2 个答案: