4.11 运算符的否定形式 ........................................................................................................... 9
五、 order by 子句 ....................................................................................................................... 10
5.1 语法和执行顺序 ............................................................................................................... 10
5.2 升降序 ............................................................................................................................... 10
5.3 null 值在排序中显示 ....................................................................................................... 10
5.4 order by 后面可以跟什么 ................................................................................................ 10
5.5 多列排序 ........................................................................................................................... 10
六、 单行函数的使用.................................................................................................................. 11
6.1 数值类型 ........................................................................................................................... 11
6.2 日期类型 ........................................................................................................................... 11
6.3 字符类型 ........................................................................................................................... 13
6.4 转换函数 ........................................................................................................................... 14
6.5 其他注意事项 ................................................................................................................... 14
七、 SQL 语句中的分支 ............................................................................................................. 15
7.1 分支表达式 ....................................................................................................................... 15
7.2 分支函数 ........................................................................................................................... 15
八、 组函数 ................................................................................................................................. 16
8.1 报表统计常用 ................................................................................................................... 16
8.2 缺省情况组函数处理什么值 ........................................................................................... 16
8.3 当组函数要处理的所有值都为 null 时 ........................................................................... 16
8.4 行级信息和组级信息 ....................................................................................................... 16
九、 group by 子句 ...................................................................................................................... 17
9.1 语法和执行顺序 ............................................................................................................... 17
9.2 分组过程 ........................................................................................................................... 17
9.3 常见错误 ........................................................................................................................... 17
9.4 多列分组 ........................................................................................................................... 17
十、 having 子句 .......................................................................................................................... 18
10.1 语法和执行顺序 ............................................................................................................. 18
10.2 执行过程 ......................................................................................................................... 18
10.3 where 和 having 区别 ..................................................................................................... 18
十一、 非关联子查询 ................................................................................................................. 19
11.1 语法 ................................................................................................................................. 19
11.2 子查询的执行过程 ......................................................................................................... 19
11.3 常见错误 ......................................................................................................................... 19
11.4 子查询与空值 ................................................................................................................. 19
11.5 多列子查询 ..................................................................................................................... 20
十二、 关联子查询 ..................................................................................................................... 21
12.1 语法 ................................................................................................................................. 21
12.2 执行过程 ......................................................................................................................... 21
12.3 exists ............................................................................................................................... 21
12.4 exists 执行过程 ............................................................................................................... 21
12.5 not exists ......................................................................................................................... 22
12.6 not exists 执行过程 ........................................................................................................ 22
12.7 in 和 exists 比较 ............................................................................................................. 22
