| 列别名 | SELECT price * qty AS amount |
|---|---|
| 表别名 | FROM order_items AS oi |
| 带空格别名 | MySQL 用反引号，PostgreSQL 用双引号 |
示例
示例
SELECT u.id,
u.name AS user_name,
o.amount AS order_amount
FROM users AS u
JOIN orders AS o ON o.user_id = u.id;带空格/特殊字符的别名
带空格/特殊字符的别名
-- MySQL
SELECT 1 AS `total count`;
-- PostgreSQL
SELECT 1 AS "total count";PostgreSQL 中双引号会保留大小写，"total count" 与 total count 不是同一个名字。