sql - MySQL 到 PostgreSQL : How to modify this SQL query?

Question

我有一个使用 MONTH() 和 YEAR() 的 MySQL 查询:

SELECT 
  MONTH(created_at) AS month, 
  YEAR(created_at) AS year 
FROM users 
GROUP BY MONTH(created_at), YEAR(created_at) 
ORDER BY YEAR(created_at), MONTH(created_at)

如何修改该查询以与 PostgreSQL 配合使用？

Answer 1

SELECT 
  extract(MONTH from created_at) AS month, 
  extract(YEAR from created_at) AS year 
FROM users 
GROUP BY extract(MONTH from created_at), extract(YEAR from created_at) 
ORDER BY extract(MONTH from created_at), extract(YEAR from created_at) 

这是最新的手册
http://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-EXTRACT

顺便说一句:这是标准 (ANSI) SQL，也适用于 MySQL。