几个月前，我从一个关于堆栈溢出的回答中学到了如何使用以下语法在MySQL中一次执行多个更新:
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，显然这是不对的.它指的是所有正确的表，所以我认为这是使用不同关键字的问题，但我不确定PostgreSQL文档中在哪里涉及到了这一点.
为了澄清，我想插入一些东西，如果它们已经存在，请更新它们.
自9.5版以来，PostgreSQL有UPSERT种语法，其中101 clause.种语法如下(类似于MySQL)
INSERT INTO the_table (id, column_1, column_2)
VALUES (1, 'A', 'X'), (2, 'B', 'Y'), (3, 'C', 'Z')
ON CONFLICT (id) DO UPDATE
SET column_1 = excluded.column_1,
column_2 = excluded.column_2;
在postgresql的邮箱组存档中搜索"upsert"，可以找到an example of doing what you possibly want to do, in the manual个:
Example 38-2. Exceptions with UPDATE/INSERT
本例使用异常处理来执行更新或插入(视情况而定):
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');
可能有一个例子说明了如何批量执行此操作，使用9.1及以上版本中的CTE，在hackers mailing list中:
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;
请参见a_horse_with_no_name's answer以获得更清晰的示例.