mysql常用命令详解大全(二)之mysql查询语句select

1、查询语句（mysql更能最强的语句）

mysql> select author_id from authors;+-----------+| author_id |+-----------+|         1 |+-----------+1 row in set (0.00 sec)mysql> select author_last from authors;+-------------+| author_last |+-------------+| Greene      |+-------------+1 row in set (0.00 sec)mysql> select * from authors;+-----------+-------------+--------------+----------------+| author_id | author_last | author_first | country        |+-----------+-------------+--------------+----------------+|         1 | Greene      | Graham       | United Kingdom ||         2 | summer      | andy         | chine          |+-----------+-------------+--------------+----------------+2 rows in set (0.00 sec)

*是通配符，表示选择了所用的列，你也可以选择指定的列，在select 后面列出你写选择的列，并用逗号隔开。

使用where 可以选择指定的行。

更复杂的双表查询语句

mysql> select book_id,title,pub_year,    -> concat(author_first,' ',author_last) as  author    -> from books    -> join authors using (author_id)    -> where author_last='Greene';+---------+-----------------------+----------+---------------+| book_id | title                 | pub_year | author        |+---------+-----------------------+----------+---------------+|       1 | The End of the Affair | 1951     | Graham Greene |+---------+-----------------------+----------+---------------+

concat字符串连接函数，将concat所有的字符串连接起来作为一个字符串

as 根据我们指定的名称创建列标题，我们称这个列标题为别名。