where子句、group by子句、having子句在select语句中的顺序是()
A. having子句、group by子句、where子句
B. group by子句、having子句、where子句
C. group by子句、where子句、having子句
D. where子句、group by子句、having子句
分组查询中,去掉不需要的组用( )关键字。
A. having
B. where
C. group by
D. from
为用户表添加姓名字段的语句是()
A. alter table user add name varchar(40);
B. alter table user drop name;
C. alter table user rename oldname to newname;
D. alter table user alter name varchar(50);
为用户表删除姓名字段的语句是()
A. alter table user add name varchar(40);
B. alter table user drop name;
C. alter table user rename oldname to newname;
D. alter table user alter name varchar(50);