PostgreSQL类似Oracle merge into功能的实现

MERGE语句是Oracle9i新增的语法，用来合并UPDATE和INSERT语句。通过MERGE语句，根据一张表或子查询的连接条件对另外一张表进行查询，连接条件匹配上的进行UPDATE，无法匹配的执行INSERT。这个语法仅需要一次全表扫描就完成了全部工作，执行效率要高于INSERT＋UPDATE

WITH upsert AS (
		UPDATE test1
		SET col1 = test2.col1
		FROM test2
		WHERE test1.id = test2.id
		RETURNING test1.*
	)
INSERT INTO test01
SELECT *
FROM test2
WHERE NOT EXISTS (
	SELECT 1
	FROM upsert b
	WHERE test2.id = b.id
);

oracle一张表向另一张表插入不重复数据merge into用法

MERGEINTO TEST A USING TEST B
ON (A.NAME=B.NAME)
WHEN MATCHEDTHEN
UPDATE SET A.SEX='女'WHERE A.NAME='SUNZHENXING'
WHEN NOT MATCHEDTHEN
INSERT VALUES (3,'SUNZHENXING','女')