1
drop table if exists t1,t2,t3;
2
create table t1 (libname varchar(21) not null, city text, primary key (libname));
3
create table t2 (isbn varchar(21) not null, author text, title text, primary key (isbn));
4
create table t3 (isbn varchar(21) not null, libname varchar(21) not null, quantity int ,primary key (isbn,libname));
5
insert into t2 values ('001','Daffy','A duck''s life');
6
insert into t2 values ('002','Bugs','A rabbit\'s life');
7
insert into t2 values ('003','Cowboy','Life on the range');
8
insert into t2 values ('000','Anonymous','Wanna buy this book?');
9
insert into t2 values ('004','Best Seller','One Heckuva book');
10
insert into t2 values ('005','EveryoneBuys','This very book');
11
insert into t2 values ('006','San Fran','It is a san fran lifestyle');
12
insert into t2 values ('007','BerkAuthor','Cool.Berkley.the.book');
13
insert into t3 values('000','New York Public Libra','1');
14
insert into t3 values('001','New York Public Libra','2');
15
insert into t3 values('002','New York Public Libra','3');
16
insert into t3 values('003','New York Public Libra','4');
17
insert into t3 values('004','New York Public Libra','5');
18
insert into t3 values('005','New York Public Libra','6');
19
insert into t3 values('006','San Fransisco Public','5');
20
insert into t3 values('007','Berkeley Public1','3');
21
insert into t3 values('007','Berkeley Public2','3');
22
insert into t3 values('001','NYC Lib','8');
23
insert into t1 values ('New York Public Libra','New York');
24
insert into t1 values ('San Fransisco Public','San Fran');
25
insert into t1 values ('Berkeley Public1','Berkeley');
26
insert into t1 values ('Berkeley Public2','Berkeley');
27
insert into t1 values ('NYC Lib','New York');
28
select t2.isbn,city,t1.libname,count(t1.libname) as a from t3 left join t1 on t3.libname=t1.libname left join t2 on t3.isbn=t2.isbn group by city,t1.libname;
30
007 Berkeley Berkeley Public1 1
31
007 Berkeley Berkeley Public2 1
32
000 New York New York Public Libra 6
33
001 New York NYC Lib 1
34
006 San Fran San Fransisco Public 1
35
select t2.isbn,city,t1.libname,count(distinct t1.libname) as a from t3 left join t1 on t3.libname=t1.libname left join t2 on t3.isbn=t2.isbn group by city having count(distinct t1.libname) > 1;
37
007 Berkeley Berkeley Public1 2
38
000 New York New York Public Libra 2
39
select t2.isbn,city,t1.libname,count(distinct t1.libname) as a from t3 left join t1 on t3.libname=t1.libname left join t2 on t3.isbn=t2.isbn group by city having count(distinct concat(t1.libname,'a')) > 1;
41
007 Berkeley Berkeley Public1 2
42
000 New York New York Public Libra 2
43
drop table t1, t2, t3;
44
create table t1 (f1 int);
45
insert into t1 values (1);
46
create table t2 (f1 int,f2 int);
47
select t1.f1,count(distinct t2.f2),count(distinct 1,NULL) from t1 left join t2 on t1.f1=t2.f1 group by t1.f1;
48
f1 count(distinct t2.f2) count(distinct 1,NULL)
51
create table t1 (f int);
52
select count(distinct f) from t1;
56
create table t1 (a char(3), b char(20), primary key (a, b));
57
insert into t1 values ('ABW', 'Dutch'), ('ABW', 'English');
58
select count(distinct a) from t1 group by b;
63
create table t1 (f1 int, f2 int);
64
insert into t1 values (0,1),(1,2);
65
select count(distinct if(f1,3,f2)) from t1;
66
count(distinct if(f1,3,f2))