插入,在重复更新在PostgreSQL？

几个月前，我从Stack Overflow的答案学习了如何使用以下语法在MysqL中同时执行多个更新：

INSERT INTO table (id,field,field2) VALUES (1,A,X),(2,B,Y),(3,C,Z)
ON DUPLICATE KEY UPDATE field=VALUES(Col1),field2=VALUES(Col2);

我现在切换到Postgresql，显然这是不正确的。它指的是所有正确的表，所以我认为这是一个问题使用不同的关键字，但我不知道在Postgresql文档中包括这里。

为了澄清，我想插入几个东西，如果他们已经存在更新他们。

Postgresql从9.5版本开始有 UPSERT语法，带有 ON CONFLICT子句。与以下语法(类似于MysqL)

INSERT INTO the_table (id,column_1,column_2) 
VALUES (1,'A','X'),'B','Y'),'C','Z')
ON CONFLICT (id) DO UPDATE 
  SET column_1 = excluded.column_1,column_2 = excluded.column_2;

搜索postgresql的电子邮件组归档“upsert”导致找到an example of doing what you possibly want to do,in the manual：

Example 38-2. Exceptions with UPDATE/INSERT

This example uses exception handling to perform either UPDATE or INSERT,as appropriate:

CREATE TABLE db (a INT PRIMARY KEY,b TEXT);

CREATE FUNCTION merge_db(key INT,data TEXT) RETURNS VOID AS
$$
BEGIN
    LOOP
        -- first try to update the key
        -- note that "a" must be unique
        UPDATE db SET b = data WHERE a = key;
        IF found THEN
            RETURN;
        END IF;
        -- not there,so try to insert the key
        -- if someone else inserts the same key concurrently,-- we could get a unique-key failure
        BEGIN
            INSERT INTO db(a,b) VALUES (key,data);
            RETURN;
        EXCEPTION WHEN unique_violation THEN
            -- do nothing,and loop to try the UPDATE again
        END;
    END LOOP;
END;
$$
LANGUAGE plpgsql;

SELECT merge_db(1,'david');
SELECT merge_db(1,'dennis');

可能有一个例子，如何做到这一点批量，使用CTE在9.1及以上，在hackers mailing list：

WITH foos AS (SELECT (UNNEST(%foo[])).*)
updated as (UPDATE foo SET foo.a = foos.a ... RETURNING foo.id)
INSERT INTO foo SELECT foos.* FROM foos LEFT JOIN updated USING(id)
WHERE updated.id IS NULL;

更清晰的例子见a_horse_with_no_name’s answer。

插入,在重复更新在PostgreSQL？

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