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SQL学习--单表查询
source link: https://fann.im/blog/2008/04/14/sql-study-select-1/
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SQL学习--单表查询
Apr 14, 2008
指定列：select Sno,Sname from Student;
查询经过计算的值：select Sname, 'year of birth:', 2008-Sage, Sdept from student;
去除取值重复的行：select distinct Sno from student;
足条件的元组：select Sname,Sage from Student where Sdept ='CS' AND Sage<=19;
确定范围，集合 select Sname from Student where Sage BETWEEN 18 AND 20;
匹配查询 select * from Student where Sno LIKE '100%';
Order By子句 select Sno,Grade from SC where Cno ='2' ORDER BY Grade DESC; //DESC是降序，缺省为升序
聚集函数：select COUNT(Sno) from Student;
Group By子句：select Cno,COUNT(Cno) from SC GROUP BY Cno;
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