drop table if exists t1, t2;
create table t1 (grp int, a bigint unsigned, c char(10) not null, d char(10) not null);
insert into t1 values (1,1,"a","a");
insert into t1 values (2,2,"b","a");
insert into t1 values (2,3,"c","b");
insert into t1 values (3,4,"E","a");
insert into t1 values (3,5,"C","b");
insert into t1 values (3,6,"D","b");
insert into t1 values (3,7,"d","d");
insert into t1 values (3,8,"d","d");
insert into t1 values (3,9,"D","c");
select grp,group_concat(c) from t1 group by grp;
grp	group_concat(c)
1	a
2	b,c
3	E,C,D,d,d,D
explain extended select grp,group_concat(c) from t1 group by grp;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	9	Using filesort
Warnings:
Note	1003	select high_priority test.t1.grp AS `grp`,group_concat(test.t1.c seperator ',') AS `group_concat(c)` from test.t1 group by test.t1.grp
select grp,group_concat(a,c) from t1 group by grp;
grp	group_concat(a,c)
1	1a
2	2b,3c
3	4E,5C,6D,7d,8d,9D
select grp,group_concat("(",a,":",c,")") from t1 group by grp;
grp	group_concat("(",a,":",c,")")
1	(1:a)
2	(2:b),(3:c)
3	(4:E),(5:C),(6:D),(7:d),(8:d),(9:D)
select grp,group_concat(c separator ",") from t1 group by grp;
grp	group_concat(c separator ",")
1	a
2	b,c
3	E,C,D,d,d,D
select grp,group_concat(c separator "---->") from t1 group by grp;
grp	group_concat(c separator "---->")
1	a
2	b---->c
3	E---->C---->D---->d---->d---->D
select grp,group_concat(c order by c) from t1 group by grp;
grp	group_concat(c order by c)
1	a
2	b,c
3	C,D,d,d,D,E
select grp,group_concat(c order by c desc) from t1 group by grp;
grp	group_concat(c order by c desc)
1	a
2	c,b
3	E,D,d,d,D,C
select grp,group_concat(d order by a) from t1 group by grp;
grp	group_concat(d order by a)
1	a
2	a,b
3	a,b,b,d,d,c
select grp,group_concat(d order by a desc) from t1 group by grp;
grp	group_concat(d order by a desc)
1	a
2	b,a
3	c,d,d,b,b,a
select grp,group_concat(a order by a,d+c) from t1 group by grp;
grp	group_concat(a order by a,d+c)
1	1
2	2,3
3	4,5,6,7,8,9
select grp,group_concat(c order by 1) from t1 group by grp;
grp	group_concat(c order by 1)
1	a
2	b,c
3	C,D,d,d,D,E
select grp,group_concat(c order by "c") from t1 group by grp;
grp	group_concat(c order by "c")
1	a
2	b,c
3	C,D,d,d,D,E
select grp,group_concat(distinct c order by c) from t1 group by grp;
grp	group_concat(distinct c order by c)
1	a
2	b,c
3	C,D,E
select grp,group_concat(distinct c order by c desc) from t1 group by grp;
grp	group_concat(distinct c order by c desc)
1	a
2	c,b
3	E,D,C
explain extended select grp,group_concat(distinct c order by c desc) from t1 group by grp;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	9	Using filesort
Warnings:
Note	1003	select high_priority test.t1.grp AS `grp`,group_concat(distinct test.t1.c order by test.t1.c seperator ',') AS `group_concat(distinct c order by c desc)` from test.t1 group by test.t1.grp
select grp,group_concat(c order by c separator ",") from t1 group by grp;
grp	group_concat(c order by c separator ",")
1	a
2	b,c
3	C,D,d,d,D,E
select grp,group_concat(c order by c desc separator ",") from t1 group by grp;
grp	group_concat(c order by c desc separator ",")
1	a
2	c,b
3	E,D,d,d,D,C
select grp,group_concat(distinct c order by c separator ",") from t1 group by grp;
grp	group_concat(distinct c order by c separator ",")
1	a
2	b,c
3	C,D,E
explain extended select grp,group_concat(distinct c order by c separator ",") from t1 group by grp;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	9	Using filesort
Warnings:
Note	1003	select high_priority test.t1.grp AS `grp`,group_concat(distinct test.t1.c order by test.t1.c seperator ',') AS `group_concat(distinct c order by c separator ",")` from test.t1 group by test.t1.grp
select grp,group_concat(distinct c order by c desc separator ",") from t1 group by grp;
grp	group_concat(distinct c order by c desc separator ",")
1	a
2	c,b
3	E,D,C
select grp,group_concat(c order by grp desc) from t1 group by grp order by grp;
grp	group_concat(c order by grp desc)
1	a
2	c,b
3	D,d,d,D,C,E
select grp, group_concat(a separator "")+0 from t1 group by grp;
grp	group_concat(a separator "")+0
1	1
2	23
3	456789
select grp, group_concat(a separator "")+0.0 from t1 group by grp;
grp	group_concat(a separator "")+0.0
1	1.0
2	23.0
3	456789.0
select grp, ROUND(group_concat(a separator "")) from t1 group by grp;
grp	ROUND(group_concat(a separator ""))
1	1
2	23
3	456789
drop table t1;
create table t1 (grp int, c char(10));
insert into t1 values (1,NULL);
insert into t1 values (2,"b");
insert into t1 values (2,NULL);
insert into t1 values (3,"E");
insert into t1 values (3,NULL);
insert into t1 values (3,"D");
insert into t1 values (3,NULL);
insert into t1 values (3,NULL);
insert into t1 values (3,"D");
insert into t1 values (4,"");
insert into t1 values (5,NULL);
select grp,group_concat(c order by c) from t1 group by grp;
grp	group_concat(c order by c)
1	NULL
2	b
3	D,D,E
4	
5	NULL
set group_concat_max_len = 5;
select grp,group_concat(c) from t1 group by grp;
grp	group_concat(c)
1	NULL
2	b
3	D,D,E
4	
5	NULL
Warnings:
Warning	1259	1 line(s) was(were) cut by group_concat()
show warnings;
Level	Code	Message
Warning	1259	1 line(s) was(were) cut by group_concat()
set group_concat_max_len = 1024;
select group_concat(sum(a)) from t1 group by grp;
ERROR HY000: Invalid use of group function
select grp,group_concat(c order by 2) from t1 group by grp;
ERROR 42S22: Unknown column '2' in 'group statement'
drop table t1;
create table t1 ( URL_ID int(11), URL varchar(80));
create table t2 ( REQ_ID int(11), URL_ID int(11));
insert into t1 values (4,'www.host.com'), (5,'www.google.com'),(5,'www.help.com');
insert into t2 values (1,4), (5,4), (5,5);
select REQ_ID, Group_Concat(URL) as URL from t1, t2 where 
t2.URL_ID = t1.URL_ID group by REQ_ID;
REQ_ID	URL
1	X
5	X,X,X
select REQ_ID, Group_Concat(URL) as URL, Min(t1.URL_ID) urll,
Max(t1.URL_ID) urlg from t1, t2 where t2.URL_ID = t1.URL_ID group by REQ_ID;
REQ_ID	URL	urll	urlg
1	X	4	4
5	X,X,X	4	5
drop table t1;
drop table t2;
create table t1 (id int, name varchar(16));
insert into t1 values (1,'longername'),(1,'evenlongername');
select ifnull(group_concat(concat(t1.id, ':', t1.name)), 'shortname') as 'without distinct: how it should be' from t1;
without distinct: how it should be
1:longername,1:evenlongername
select distinct ifnull(group_concat(concat(t1.id, ':', t1.name)), 'shortname') as 'with distinct: cutoff at length of shortname' from t1;
with distinct: cutoff at length of shortname
1:longername,1:evenlongername
drop table t1;
create table t1(id int);
create table t2(id int);
insert into t1 values(0),(1);
select group_concat(t1.id) FROM t1,t2;
group_concat(t1.id)
NULL
drop table t1;
drop table t2;
create table t1 (bar varchar(32));
insert into t1 values('test'),('test2');
select * from t1 having group_concat(bar)='';
bar
drop table t1;
create table t1 (a int, a1 varchar(10));
create table t2 (a0 int);
insert into t1 values (0,"a"),(0,"b"),(1,"c");
insert into t2 values (1),(2),(3);
select  group_concat(a1 order by (t1.a IN (select a0 from t2))) from t1;
group_concat(a1 order by (t1.a IN (select a0 from t2)))
b,a,c
select  group_concat(a1 order by (t1.a)) from t1;
group_concat(a1 order by (t1.a))
b,a,c
drop table t1, t2;