mySQL简单操作（二）

1、like子句

[where clause like '%com']

• '%'
• '_'

2、正则

3、union操作符

用于连接多个select语句，[distinct]删除重复数据

select col1, ......, coln from tbl_name

[where clause]

union [all(默认) / distinct]

select col1, ......, coln from tbl_name

[where clause]

4、order by 排序

select col1, ......, coln from tbl_name

[where clause]

order by col1,...... [ASC(默认） / DESC]

• gbk(汉字编码字符集）
• utf-8(万国码）:order by convert (col1, ...... using gbk)  [ASC(默认） / DESC]

5、group by 分组语句

select col1, ......, function(coln) from tbl_name

[where clause]

[group by col1]

[having clause]

[order by ......]

6、join 内连接

• left jpin
• join 或 inner join
• right join

以下两句等价：

（1）select tbl1.col1, tbl1.col2, tbl2.col3

from tbl_name1 tbl1 join tbl_name2 tbl2 on tbl1.col3 = tbl2.col3

（2）select tbl1.col1, tbl1.col2, tbl2.col3 from tbl_name1 tbl1, tbl_name2 tbl2

where tbl1.col3 = tbl2.col3