MySQL 查询表达式，别名

查询记录

SELECT select_expr [, select_expr ...]

[

FROM table_reference

[WHERE 条件]

[GROUP BY {col_name|position} [ASC|DESC], ...分组]

[HAVING 条件 对分组结果进行二次筛选]

[ORDER BY  {col_name|position} [ASC|DESC], ...排序]

[LIMIT 限制显示条数]

]

查询表达式

*表示所有列，  tablename.* 表示表的所有列

别名

name [AS] alias_name

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例子

SELECT id, emails FROM sss;

SELECT s.id, s.username FROM sss AS s;

SELECT s.id AS ID, s.username AS User FROM sss AS s;

SELECT id,emails FROM KAKA1.SSS; #不打开库的情况下，用其表