Question

我在Netezza中使用if not exists语句时遇到问题。我试图检查记录是否不存在然后插入其他更新记录。我在Netezza找不到更好的办法。这是我有的但不起作用：

IF NOT EXISTS(SELECT ID FROM OLD_TABLE WHERE ID NOT IN (SELECT ID FROM NEW TABLE ) )
INSERT INTO NEW_TABLE (NAME, LOCATION)
ELSE 
UPDATE NEW_TABLE
SET NAME = X.NAME
FROM (SELECT NAME, LOCATION FROM OLD_TABLE)AS X
WHERE X.NAME = NEW_TABLE.NAME

Answer 1

假设您提供了一个ID，并希望在new_table中使用来自old_table的值替换一行。我使用的是data-modifying CTE，需要Postgres 9.1或更高版本：

WITH input AS (SELECT 123 AS id)
, upd AS (
   UPDATE new_table n
   SET    name = o.name
        , location = o.location
   FROM   old_table o, input i
   WHERE  n.id = o.id
   AND    n.id = i.id
   RETURNING id
   )
INSERT INTO new_table (id, name, location)
SELECT o.id, o.name, o.location
FROM   old_table o, input i 
WHERE  NOT EXISTS (SELECT 1 FROM upd)
AND    o.id = i.id;

这是一个密切相关的答案，有更多解释：
Problems with a PostgreSQL upsert query

竞争条件很小。如果您计划在繁重的并发负载下使用此功能，请考虑此相关问题以及更多链接：
Upsert with a transaction

整张桌子

要整张整个表格：

WITH upd AS (
   UPDATE new_table n
   SET    name = o.name
        , location = o.location
   FROM   old_table o
   WHERE  n.id = o.id
   RETURNING id
   )
INSERT INTO new_table (id, name, location)
SELECT o.id, o.name, o.location
FROM   old_table o
LEFT   JOIN upd u USING (id)
WHERE  u.id IS NULL;

插入如果不存在，则在Netezza中更新它

1 个答案:

整张桌子