drop table if exists t1;
Warnings:
Note	1051	Unknown table 't1'
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
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
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
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	1258	1 line(s) was(were) cut by group_concat()
show warnings;
Level	Code	Message
Warning	1258	1 line(s) was(were) cut by group_concat()
set group_concat_max_len = 1024;
drop table if exists T_URL;
Warnings:
Note	1051	Unknown table 'T_URL'
create table T_URL ( URL_ID int(11), URL varchar(80));
drop table if exists T_REQUEST;
Warnings:
Note	1051	Unknown table 'T_REQUEST'
create table T_REQUEST ( REQ_ID int(11), URL_ID int(11));
insert into T_URL values (4,'www.host.com'), (5,'www.google.com'),(5,'www.help.com');
insert into T_REQUEST values (1,4), (5,4), (5,5);
select REQ_ID, Group_Concat(URL) as URL from T_URL, T_REQUEST where 
T_REQUEST.URL_ID = T_URL.URL_ID group by REQ_ID;
REQ_ID	URL
1	www.host.com
5	www.host.com,www.google.com,www.help.com
drop table T_URL;
drop table T_REQUEST;
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;