如果不存在,如何插入

Question

我试图在表中插入数据,但如果它已经存在于表中,那么它不应该添加.
这是代码,我提出的,但它仍然添加了具有相同值的多个数据.

insert into nol_art_izm([ART_ID],[DAT])
    select distinct
        v.id_art, {fn now()}
    from
        openxml(@hDoc, '/art_kompl/nol_voac') with #vc xd
        inner join nol_voac v on xd.id_art = v.id_art
    where
        not exists(select * from nol_art_izm where nol_art_izm.art_id=xd.id_art)

我希望没有任何重复的"ART_ID"值

Answer 1

注意:此答案仅适用于SQL Server 2008 ...

使用该MERGE声明.MERGE声明的优点在于它清楚地表达了仅在没有匹配时才想要插入的意图.对于未来的读者来说,这可能会有所帮助,因为涉及INSERT .. SELECT的替代方案对于解密来说有点棘手.

-- This is where you're "merging" data into
MERGE INTO nol_art_izm dst

-- This is your merge data source
USING (
  -- Use DISTINCT here, to prevent possible duplicates from the below INNER JOIN
  SELECT DISTINCT v.id_art 
  FROM openxml(@hDoc, '/art_kompl/nol_voac') with #vc xd
  INNER JOIN nol_voac v on xd.id_art = v.id_art
) src

-- This is your "join" condition, used to decide whether to perform an
-- INSERT or UPDATE
ON (dst.art_id = src.id_art)

-- When source and target don't match (see ON clause), perform an insert
WHEN NOT MATCHED THEN INSERT ([ART_ID],[DAT])
  VALUES (src.id_art, {fn now()})

本声明省略了该WHEN MATCHED THEN UPDATE条款,因为您只对表演感兴趣INSERTs,而不是UPDATEs