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SET @save = @@global.group_concat_max_len;
DROP TABLE IF EXISTS t1;
## Creating new table t1 ##
CREATE TABLE t1
(
id INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY (id),
rollno INT NOT NULL,
name VARCHAR(30)
);
'#--------------------FN_DYNVARS_034_01-------------------------#'
## Setting initial value of variable to 4 ##
SET @@global.group_concat_max_len = 4;
## Inserting some rows in table ##
INSERT INTO t1(rollno, name) VALUES(1, 'Record_1');
INSERT INTO t1(rollno, name) VALUES(2, 'Record_2');
INSERT INTO t1(rollno, name) VALUES(1, 'Record_3');
INSERT INTO t1(rollno, name) VALUES(3, 'Record_4');
INSERT INTO t1(rollno, name) VALUES(1, 'Record_5');
INSERT INTO t1(rollno, name) VALUES(3, 'Record_6');
INSERT INTO t1(rollno, name) VALUES(4, 'Record_7');
INSERT INTO t1(rollno, name) VALUES(4, 'Record_8');
SELECT * FROM t1 ORDER BY id;
id rollno name
1 1 Record_1
2 2 Record_2
3 1 Record_3
4 3 Record_4
5 1 Record_5
6 3 Record_6
7 4 Record_7
8 4 Record_8
connect test_con1,localhost,root,,;
connect test_con2,localhost,root,,;
'#--------------------FN_DYNVARS_034_02-------------------------#'
connection test_con1;
## Accessing data and using group_concat on column whose value is greater than 4 ##
SELECT id, rollno, GROUP_CONCAT(name) FROM t1 GROUP BY rollno;
id rollno GROUP_CONCAT(name)
1 1 Reco
2 2 Reco
4 3 Reco
7 4 Reco
Warnings:
Warning 1260 Row 1 was cut by group_concat()
Warning 1260 Row 2 was cut by group_concat()
Warning 1260 Row 3 was cut by group_concat()
Warning 1260 Row 4 was cut by group_concat()
## Changing session value of variable and verifying its behavior, ##
## warning should come here ##
SET @@session.group_concat_max_len = 10;
SELECT id, rollno, GROUP_CONCAT(name) FROM t1 GROUP BY rollno;
id rollno GROUP_CONCAT(name)
1 1 Record_1,R
2 2 Record_2
4 3 Record_4,R
7 4 Record_7,R
Warnings:
Warning 1260 Row 2 was cut by group_concat()
Warning 1260 Row 5 was cut by group_concat()
Warning 1260 Row 7 was cut by group_concat()
'#--------------------FN_DYNVARS_034_03-------------------------#'
connection test_con2;
## Verifying initial value of variable. It should be 4 ##
SELECT @@session.group_concat_max_len = 4;
@@session.group_concat_max_len = 4
1
## Setting session value of variable to 20 and verifying variable is concating ##
## column's value to 20 or not ##
SET @@session.group_concat_max_len = 20;
## Verifying value of name column, it should not me more than 20 characters ##
## Warning should come here ##
SELECT id, rollno, GROUP_CONCAT(name) FROM t1 GROUP BY rollno;
id rollno GROUP_CONCAT(name)
1 1 Record_1,Record_3,Re
2 2 Record_2
4 3 Record_4,Record_6
7 4 Record_7,Record_8
Warnings:
Warning 1260 Row 3 was cut by group_concat()
'#--------------------FN_DYNVARS_034_04-------------------------#'
## Setting session value of variable to 26. No warning should appear here ##
## because the value after concatination is less than 30 ##
SET @@session.group_concat_max_len = 26;
## Verifying value of name column, it should not give warning now ##
SELECT id, rollno, GROUP_CONCAT(name) FROM t1 GROUP BY rollno;
id rollno GROUP_CONCAT(name)
1 1 Record_1,Record_3,Record_5
2 2 Record_2
4 3 Record_4,Record_6
7 4 Record_7,Record_8
## Dropping table t1 ##
DROP TABLE t1;
disconnect test_con2;
disconnect test_con1;
connection default;
CREATE TABLE t1(val VARCHAR(100) PRIMARY KEY) CHARACTER SET utf8mb4 COLLATE utf8mb4_danish_ci;
INSERT INTO t1 VALUES('bar');
INSERT INTO t1 VALUES('foo');
SET group_concat_max_len = 1073741823;
SHOW VARIABLES LIKE 'group_concat_max_len';
Variable_name Value
group_concat_max_len 1073741823
SELECT GROUP_CONCAT(val) AS simple FROM t1;
simple
bar,foo
SELECT * FROM ( SELECT GROUP_CONCAT(val) AS nested FROM t1) As tmp;
nested
bar,foo
SET group_concat_max_len = 1073741824;
SHOW VARIABLES LIKE 'group_concat_max_len';
Variable_name Value
group_concat_max_len 1073741824
SELECT GROUP_CONCAT(val) AS simple FROM t1;
simple
bar,foo
SELECT * FROM ( SELECT GROUP_CONCAT(val) AS nested FROM t1) As tmp;
nested
bar,foo
SET group_concat_max_len = 1073741825;
SHOW VARIABLES LIKE 'group_concat_max_len';
Variable_name Value
group_concat_max_len 1073741825
SELECT GROUP_CONCAT(val) AS simple FROM t1;
simple
bar,foo
SELECT * FROM ( SELECT GROUP_CONCAT(val) AS nested FROM t1) As tmp;
nested
bar,foo
SET group_concat_max_len = 1073741826;
SHOW VARIABLES LIKE 'group_concat_max_len';
Variable_name Value
group_concat_max_len 1073741826
SELECT GROUP_CONCAT(val) AS simple FROM t1;
simple
bar,foo
SELECT * FROM ( SELECT GROUP_CONCAT(val) AS nested FROM t1) As tmp;
nested
bar,foo
SET group_concat_max_len = 2147483649;
SHOW VARIABLES LIKE 'group_concat_max_len';
Variable_name Value
group_concat_max_len 2147483649
SELECT GROUP_CONCAT(val) AS simple FROM t1;
simple
bar,foo
SELECT * FROM ( SELECT GROUP_CONCAT(val) AS nested FROM t1) As tmp;
nested
bar,foo
DROP TABLE t1;
SET @@global.group_concat_max_len = @save;
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