DROP TABLE IF EXISTS n_select;
CREATE TABLE n_select(
name varchar(10) NOT NULL default '',
count char(10) NOT NULL default '',
score_one FLOAT(3) NOT NULL default 0,
score_two FLOAT(3) NOT NULL default 0
)TYPE=MyISAM;INSERT INTO n_select values('aaa','3-17','2.7','2.4');
INSERT INTO n_select values('bbb','3-17','1.6','1.8');
INSERT INTO n_select values('ccc','3-17','0.7','0.9');
INSERT INTO n_select values('aaa','3-18','2.1','2.3');
INSERT INTO n_select values('bbb','3-18','1.5','1.4');
INSERT INTO n_select values('ccc','3-18','0.6','0.8');
INSERT INTO n_select values('aaa','3-19','2.5','2.9');
INSERT INTO n_select values('bbb','3-19','1.2','1.1');
INSERT INTO n_select values('ccc','3-19','0.3','0.7');
SQL语句的目的:通过一次查询,将count分别等于'3-17','3-18'和'3-19'的每个用户的两次成绩之和取出来,并按他们的成绩和DESC排序。最后想得到这样的数据结果:name score
aaa 14.9
bbb 8.6
ccc 4.0
from tb
where count in ('3-17','3-18','3-19')
group by name
from n_test
where count in('3-17','3-18','3-19')
group by name;
from n_select
where `count` in ('3-17','3-18','3-19')
group by 2 desc
from n_select
where `count` in ('3-17','3-18','3-19')
group by name
order by 2 desc