Question

假设我做了一个与

之类的条件匹配的合并

MERGE TargetTable WITH(HOLDLOCK) AS target
USING SourceTable AS source
ON (target.ID = source.ID)
WHEN MATCHED AND (source.BitCondition = 0) THEN
    UPDATE TargetTable
WHEN NOT MATCHED -- what is not matched??
    INSERT INTO TargetTable

不匹配的记录是否不在两个表中，或者就像

NOT(MATCHED AND (source.BitCondition = 0))

N.B。我故意想忽略它匹配的情况和BitCondition = 1

Answer 1

根据MERGE documentation，export const fetchBeerWithComments =(parameter) => async dispatch => {...的默认值为NOT MATCHED，表示该行存在于源{但不是NOT MATCHED BY TARGET的目标。

为避免使用MERGE插入不匹配的行，您可以添加source.BitCondition = 1条件：

AND

Answer 2

简单地说，它只是记录不在两个表中的记录＆＃34;。从技术上讲，NOT MATCHED仅使用ON <merge_search_condition>子句中定义的条件进行评估。

换句话说，您可以将MATCHED视为<merge_search_condition>的别名。

因此您的查询可以写成（伪代码）

MERGE ...
ON (target.ID = source.ID)
WHEN (target.ID = source.ID) AND (source.BitCondition = 0) THEN
    UPDATE TargetTable
WHEN NOT (target.ID = source.ID) 
    INSERT INTO TargetTable

T-SQL MERGE与条件不匹配？

2 个答案: