今天在做round()嵌套使用avg()函数的时候,出现一些小错误:即as的用法有些模糊,导致sql出错。下面先来看看round()函数:
数据库对小数进行四舍五入保留:round(字段名,保留小数位)from table b.
我写的查询语句如下:
1.ROUND(avg(name),2)name,
2.ROUND(avg(name),2)
3.ROUND(avg(name) as name,2)name,
4.ROUND(avg(name)as name,2) as name,
5.ROUND(avg(name),2) as name,(正确)
总结:as的用法一般分为两种:给结果集取别名,给列取别名
1.select * from (select * from b ) as a,as可用可不用
2.select name asname1,sex from a
Ucase()、Lcase()分别表示对字母大小写的转换,例如表table1
text
a
b
c
select Ucase(text) from table1;
结果如下:
text
A
B
C
select lcase(Ucase(text)) as text1 from table1;
结果如下:
text1
a
b
c