pgsql 分组查询方法

• group by

  group by 查询的字段 必须出现在分组中。因此这里用 max 函数，来查其他字段

SELECT
	 "max"("name") as "name",
	 "max"("organization_id") as "organizationId",
	 account
FROM
	system_users 
GROUP BY account

• PARTITION BY

Partition By是分组但不聚合

是按 account 进行分组且组内按 create_time 进行升序，返回组内行编号

rownum = 1 可以实现去重的效果

WITH res AS (
SELECT
	 organization_id,
	 "name",
	 account,
	 ROW_NUMBER() OVER(PARTITION BY "account" ORDER BY "create_time" ASC nulls last) AS rownum
FROM
	system_users 
)
SELECT * FROM res WHERE rownum = 1