1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
|
drop table if exists t1,t2,t3;
create table t1 (libname varchar(21) not null, city text, primary key (libname));
create table t2 (isbn varchar(21) not null, author text, title text, primary key (isbn));
create table t3 (isbn varchar(21) not null, libname varchar(21) not null, quantity int ,primary key (isbn,libname));
insert into t2 values ('001','Daffy','A duck''s life');
insert into t2 values ('002','Bugs','A rabbit\'s life');
insert into t2 values ('003','Cowboy','Life on the range');
insert into t2 values ('000','Anonymous','Wanna buy this book?');
insert into t2 values ('004','Best Seller','One Heckuva book');
insert into t2 values ('005','EveryoneBuys','This very book');
insert into t2 values ('006','San Fran','It is a san fran lifestyle');
insert into t2 values ('007','BerkAuthor','Cool.Berkley.the.book');
insert into t3 values('000','New York Public Libra','1');
insert into t3 values('001','New York Public Libra','2');
insert into t3 values('002','New York Public Libra','3');
insert into t3 values('003','New York Public Libra','4');
insert into t3 values('004','New York Public Libra','5');
insert into t3 values('005','New York Public Libra','6');
insert into t3 values('006','San Fransisco Public','5');
insert into t3 values('007','Berkeley Public1','3');
insert into t3 values('007','Berkeley Public2','3');
insert into t3 values('001','NYC Lib','8');
insert into t1 values ('New York Public Libra','New York');
insert into t1 values ('San Fransisco Public','San Fran');
insert into t1 values ('Berkeley Public1','Berkeley');
insert into t1 values ('Berkeley Public2','Berkeley');
insert into t1 values ('NYC Lib','New York');
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;
isbn city libname a
007 Berkeley Berkeley Public1 1
007 Berkeley Berkeley Public2 1
000 New York New York Public Libra 6
001 New York NYC Lib 1
006 San Fran San Fransisco Public 1
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;
isbn city libname a
007 Berkeley Berkeley Public1 2
000 New York New York Public Libra 2
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;
isbn city libname a
007 Berkeley Berkeley Public1 2
000 New York New York Public Libra 2
select t2.isbn,city,@bar:=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;
isbn city @bar:=t1.libname a
007 Berkeley Berkeley Public1 2
000 New York New York Public Libra 2
SELECT @bar;
@bar
Berkeley Public2
select t2.isbn,city,concat(@bar:=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;
isbn city concat(@bar:=t1.libname) a
007 Berkeley Berkeley Public1 2
000 New York New York Public Libra 2
SELECT @bar;
@bar
Berkeley Public2
drop table t1, t2, t3;
create table t1 (f1 int);
insert into t1 values (1);
create table t2 (f1 int,f2 int);
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;
f1 count(distinct t2.f2) count(distinct 1,NULL)
1 0 0
drop table t1,t2;
create table t1 (f int);
select count(distinct f) from t1;
count(distinct f)
0
drop table t1;
create table t1 (a char(3), b char(20), primary key (a, b));
insert into t1 values ('ABW', 'Dutch'), ('ABW', 'English');
select count(distinct a) from t1 group by b;
count(distinct a)
1
1
drop table t1;
create table t1 (f1 int, f2 int);
insert into t1 values (0,1),(1,2);
select count(distinct if(f1,3,f2)) from t1;
count(distinct if(f1,3,f2))
2
drop table t1;
create table t1 (i int);
insert into t1 values (0), (1);
create view v1 as select * from t1;
select count(distinct i) from v1;
count(distinct i)
2
drop table t1;
drop view v1;
create table t1 (user_id char(64) character set utf8);
insert t1 values(1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12),(13),(14),(15),(16),(17);
set @@tmp_table_size = 1024;
select count(distinct user_id) from t1;
count(distinct user_id)
17
alter table t1 modify user_id char(128) character set utf8;
select count(distinct user_id) from t1;
count(distinct user_id)
17
drop table t1;
set @@tmp_table_size = default;
|
