PS：SQL进行复杂条件运算，连表，内连，交集，并集等。

SQL 实例

初始化表结构

create table student(  
sno varchar2(10) primary key,  
sname varchar2(20),  
sage number(2),  
ssex varchar2(5)  
);  
create table teacher(  
tno varchar2(10) primary key,  
tname varchar2(20)  
);  
create table course(  
cno varchar2(10),  
cname varchar2(20),  
tno varchar2(20),  
constraint pk_course primary key (cno,tno)  
);  
create table sc(  
sno varchar2(10),  
cno varchar2(10),  
score number(4,2),  
constraint pk_sc primary key (sno,cno)  
);  
#/*******初始化学生表的数据******/  
insert into student values ('s001','张三',23,'男');  
insert into student values ('s002','李四',23,'男');  
insert into student values ('s003','吴鹏',25,'男');  
insert into student values ('s004','琴沁',20,'女');  
insert into student values ('s005','王丽',20,'女');  
insert into student values ('s006','李波',21,'男');  
insert into student values ('s007','刘玉',21,'男');  
insert into student values ('s008','萧蓉',21,'女');  
insert into student values ('s009','陈萧晓',23,'女');  
insert into student values ('s010','陈美',22,'女');  
commit;  
#/******************初始化教师表***********************/  
insert into teacher values ('t001', '刘阳');  
insert into teacher values ('t002', '谌燕');  
insert into teacher values ('t003', '胡明星');  
commit;  
#/***************初始化课程表****************************/  
insert into course values ('c001','J2SE','t002');  
insert into course values ('c002','Java Web','t002');  
insert into course values ('c003','SSH','t001');  
insert into course values ('c004','Oracle','t001');  
insert into course values ('c005','SQL SERVER 2005','t003');  
insert into course values ('c006','C#','t003');  
insert into course values ('c007','JavaScript','t002');  
insert into course values ('c008','DIV+CSS','t001');  
insert into course values ('c009','PHP','t003');  
insert into course values ('c010','EJB3.0','t002');  
commit;  
#/***************初始化成绩表***********************/  
insert into sc values ('s001','c001',78.9);  
insert into sc values ('s002','c001',80.9);  
insert into sc values ('s003','c001',81.9);  
insert into sc values ('s004','c001',60.9);  
insert into sc values ('s001','c002',82.9);  
insert into sc values ('s002','c002',72.9);  
insert into sc values ('s003','c002',81.9);  
insert into sc values ('s001','c003',59);

复杂SQL案例

#1、查询“c001”课程比“c002”课程成绩高的所有学生的学号；  
select *  from sc a, sc b where a.sno=b.sno and a.cno='c001' and b.cno='c002' and a.score>b.score;  
#2、查询平均成绩大于60 分的同学的学号和平均成绩；  
select st.sname,ss.sco from student st,(select sno,avg(score)sco from sc group by sno)ss where st.sno=ss.sno and sco>=60;  
#3、查询所有同学的学号、姓名、选课数、总成绩；  
select st.sname,ss.* from student st,(select sno,count(score)sco,sum(score) from sc group by sno)ss where st.sno=ss.sno;  
#4、查询姓“刘”的老师的个数；  
select count(*) from teacher where tname like '%刘%';  
#5、查询没学过“谌燕”老师课的同学的学号、姓名；  
select sc.sno,acno.* from sc sc,(select co.cno from course co,(select tno from teacher where tname='谌燕')tn where co.tno<>tn.tno)acno where acno.cno=sc.cno;  
#6、查询学过“c001”并且也学过编号“c002”课程的同学的学号、姓名；  
select sa.sname,sc.sno from sc sc,(select st.sname,s.* from student st,(select sno,cno from sc where cno in('c001'))s where st.sno=s.sno)sa where sc.sno=sa.sno and sc.cno='c002';  
#7、查询学过“谌燕”老师所教的所有课的同学的学号、姓名；  
select distinct st.sname from student st,sc sc join (select cno from teacher te join course co on(te.tno=co.tno) where te.tname='谌燕')aca on(sc.cno=aca.cno) where st.sno=sc.sno;   
#9、查询所有课程成绩小于60 分的同学的学号、姓名；  
select st.sname,sc.sno from student st join sc sc on(st.sno=sc.sno)where sc.score<60;  
#10、查询没有学全所有课的同学的学号、姓名；  
select sname,st.sno,scn.cn from student st join (select distinct sno,count(*)cn from sc group by sc.sno)scn on(st.sno=scn.sno) where scn.cn=(select distinct count(cno) from course);  
select st.sname,st.sno from student st join (select sc.sno sn,count(sc.cno) cou from sc group by sc.sno) scs on st.sno=scs.sn where scs.cou <(select count(cno) from course);  
#11、查询至少有一门课与学号为“s001”的同学所学相同的同学的学号和姓名；  
select distinct st.sno, sname  
from student st  
join sc sc on (st.sno = sc.sno)  
where sc.cno in (select cno from sc where sno = 's001') and sc.sno<>'s001'; 
#13、把“SC”表中“谌燕”老师教的课的成绩都更改为此课程的平均成绩；  
#update sc sc set sc.score=update sc sc set sc.score=(select tc.cno,round(avg(sc.score),2)av from (select * from teacher te join course co on(te.tno=co.tno) where te.tname='谌燕')tc join sc sc on(tc.cno=sc.cno) group by tc.cno)cnn.score where sc.cno=cnn.av;  
select tc.cno,round(avg(sc.score),2) from (select * from teacher te join course co on(te.tno=co.tno) where te.tname='谌燕')tc join sc sc on(tc.cno=sc.cno) group by tc.cno;  
#14、查询和“s001”号的同学学习的课程完全相同的其他同学学号和姓名；  
select cno from sc where sno='s001';  
#15、删除学习“谌燕”老师课的SC 表记录；  
delete from sc where sc.cno in(select cno from teacher te join course co on(te.tno=co.tno) where te.tname='谌燕')  
#17、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分  
select cno,max(score),min(score) from sc group by cno;  
#18、按各科 平均成绩 从 低到高 和 及格率的百分数 从高到低顺序  
#select count(score) from sc where score>=60 group by cno ;  
select cno,avg(score)acs,savg.cnu,(count(score)-savg.cnu)/count(score)*100 from sc,  
(select count(score)cnu,avg(score)acs2 from sc where score<60 order by acs2 desc)savg   
group by savg.cnu,cno order by acs desc;  
#21、查询各科成绩前三名的记录:(不考虑成绩并列情况)  
select * from (select S.*,rownum rn from (select * from sc order by score desc)S where rownum<=3)where rn>=1;  
#22、查询每门课程被选修的学生数  
select cno,count(cno) from sc group by cno;  
#23、查询出只选修了一门课程的全部学生的学号和姓名  
select st.sname,st.sno from student st join   
(select distinct sc.* from sc sc join (select sno,count(cno)cnum from sc group by sno)ss on(sc.sno=ss.sno) where ss.cnum=1)ssb   
on(st.sno=ssb.sno);  
#24、查询男生、女生人数  
select ssex,count(ssex) from student st group by ssex;  
#25、查询姓“张”的学生名单  
select sname from student where sname like '%张%';  
#26、查询同名同性学生名单，并统计同名人数  
select st.* from student st join (select sname,count(sname)cnum from student group by sname)scomm on(st.sname=scomm.sname) where scomm.cnum>1;  
#27、1981 年出生的学生名单(注：Student 表中Sage 列的类型是number)  
select * from student where to_char(sysdate,'yyyy')-sage ='1981';  
#28、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列  
select cno,avg(score)lim from sc group by cno order by lim asc;  
#29、查询平均成绩大于85 的所有学生的学号、姓名和平均成绩  
select st.sname,st.sno,savg.lim from student st join (select sno,avg(score)lim from sc group by sno)savg on(st.sno=savg.sno) where savg.lim>85;  
#30、查询课程名称为“数据库”，且分数低于60 的学生姓名和分数  
select distinct st.sname,cs.score from student st join (select * from course co join sc sc on(co.cno=sc.cno))cs on(st.sno=cs.sno)where cs.score<60 and cs.cname='数据库';  
#31、查询所有学生的选课情况；  
select distinct st.sname,cs.cname from student st join (select * from course co join sc sc on(co.cno=sc.cno))cs on(st.sno=cs.sno);  
#32、查询任何一门课程成绩在70 分以上的姓名、课程名称和分数；  
select distinct st.sname,cs.score,cs.cname from student st join (select * from course co join sc sc on(co.cno=sc.cno))cs on(st.sno=cs.sno)where cs.score>70;  
#33、查询不及格的课程，并按课程号从大到小排列  
select * from sc where score<60 order by sno desc;  
#34、查询课程编号为c001 且课程成绩在80 分以上的学生的学号和姓名；  
select st.sname,st.sno from student st join (select * from sc where cno='c001' and score>80)snum on(st.sno=snum.sno);  
#35、求选了课程的学生人数  
select count(ss.sno) from (select distinct sno from sc)ss;  
#36、查询选修“谌燕”老师所授课程的学生中，成绩最高的学生姓名及其成绩  
select st.sname,cnum.score from student st join  
(select distinct * from sc sc where cno in(select distinct cno from course co join   
(select tno from teacher where tname='谌燕')ten on(co.tno=ten.tno)) order by score desc)cnum on(st.sno=cnum.sno) where rownum=1;  
#37、查询各个课程及相应的选修人数  
#(select cno,count(cno) from sc group by cno);  
select co.cname,cns.cnum from course co join (select cno,count(cno)cnum from sc group by cno)cns on(co.cno=cns.cno);  
#39、查询每门功课成绩最好的前两名  
select cno from sc order by score desc group by cno;  
#40、统计每门课程的学生选修人数（超过10 人的课程才统计）。要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列  
#41、检索至少选修两门课程的学生学号  
select sno from (select sno,count(cno)cnum from sc group by sno) where cnum>=2;  
#42、查询全部学生都选修的课程的课程号和课程名  
#select count(*) from (select distinct sno from sc);  
#select cno,count(cno)cns from sc group by cno;  
#select cno from (select count(*)num from (select distinct sno from sc))cs1,(select cno,count(cno)cns from sc group by cno)cs2 where cs2.cns=cs1.num;  
select cname,scs.cno from course co join   
(select cno from (select count(*)num from (select distinct sno from sc))cs1,  
(select cno,count(cno)cns from sc group by cno)cs2 where cs2.cns=cs1.num)scs on(co.cno=scs.cno);  
#43、查询没学过“谌燕”老师讲授的任一门课程的学生姓名  
#select co.cno from course co join (select tno from teacher where tname='谌燕')tn on(co.tno=tn.tno);  
select sname from student where sno not in  
(select distinct sno from sc where cno in(select co.cno from course co join   
(select tno from teacher where tname='谌燕')tn on(co.tno=tn.tno)));  
#44、查询两门以上不及格课程的同学的学号及其平均成绩  
#select sno,count(sno),avg(score) from sc where score < 60 group by sno;  
select * from (select sno,count(sno)cnum,avg(score) from sc where score < 60 group by sno)avs where avs.cnum>1;  
#45、检索“c004”课程分数小于60，按分数降序排列的同学学号  
select sno from sc where cno='c004' and score<60 order by score desc;  
#46、删除“s002”同学的“c001”课程的成绩  
delete from sc where sno='s002' and cno='c001';

业务Demo


        //设置查询区间为一天
$unix_end_time = $unix_start_time+86400;
//查询当天下单并且已购买的用户
$condition1 = "SELECT mobile,total_amount FROM $this->_order_table  WHERE create_time > $unix_start_time AND create_time <=$unix_end_time AND status = 4";
//查询当天下单并且未购买的用户
$condition2 = "SELECT mobile,pid,total_amount FROM $this->_order_table  WHERE create_time > $unix_start_time AND create_time <=$unix_end_time AND status != 4 " ;
//取当天下单并且已购买和当天下单未购买的用户交集,得到同一手机号重复下单用户
$condition3 = "SELECT table2.mobile FROM ($condition1) AS table1 INNER JOIN ($condition2)AS table2 ON table1.mobile = table2.mobile";
//取$condition2 和 $condition3 的差集,得到下单未购买的发券精准用户,并取所下单金额的最大值
$condition = "SELECT table3.mobile,pid,MAX(table3.total_amount) FROM ($condition2) AS table3 WHERE table3.mobile NOT IN ($condition3) GROUP BY table3.mobile";
$result = $this->_db->query($condition);