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DROP TABLE IF EXISTS t1;
SET NAMES cp932;
CREATE TABLE t1 (c1 INTEGER COMMENT '', c12 INTEGER, c13 DATETIME, c14 CHAR(10), PRIMARY KEY(c1), INDEX(c12,c13)) COMMENT='ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR';
SELECT table_comment,char_length(table_comment) FROM information_schema.tables WHERE table_name='t1';
table_comment char_length(table_comment)
ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR 60
SELECT column_comment,char_length(column_comment) FROM information_schema.columns WHERE table_name='t1';
column_comment char_length(column_comment)
60
0
0
0
SHOW CREATE TABLE t1;
Table Create Table
t1 CREATE TABLE `t1` (
`c1` int(11) NOT NULL DEFAULT '0' COMMENT '',
`c12` int(11) DEFAULT NULL,
`c13` datetime DEFAULT NULL,
`c14` char(10) DEFAULT NULL,
PRIMARY KEY (`c1`),
KEY `c12` (`c12`,`c13`)
) ENGINE=ENGINE DEFAULT CHARSET=latin1 COMMENT='ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR'
ALTER TABLE t1 ADD COLUMN c2 INTEGER COMMENT 'A';
ALTER TABLE t1 ADD COLUMN c3 INTEGER COMMENT 'C';
ALTER TABLE t1 ADD COLUMN c4 INTEGER COMMENT 'E';
ALTER TABLE t1 ADD COLUMN c5 INTEGER COMMENT 'G';
SELECT table_comment,char_length(table_comment) FROM information_schema.tables WHERE table_name='t1';
table_comment char_length(table_comment)
ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR 60
SELECT column_comment,char_length(column_comment) FROM information_schema.columns WHERE table_name='t1';
column_comment char_length(column_comment)
60
0
0
0
A 60
C 60
E 60
G 60
SHOW CREATE TABLE t1;
Table Create Table
t1 CREATE TABLE `t1` (
`c1` int(11) NOT NULL DEFAULT '0' COMMENT '',
`c12` int(11) DEFAULT NULL,
`c13` datetime DEFAULT NULL,
`c14` char(10) DEFAULT NULL,
`c2` int(11) DEFAULT NULL COMMENT 'A',
`c3` int(11) DEFAULT NULL COMMENT 'C',
`c4` int(11) DEFAULT NULL COMMENT 'E',
`c5` int(11) DEFAULT NULL COMMENT 'G',
PRIMARY KEY (`c1`),
KEY `c12` (`c12`,`c13`)
) ENGINE=ENGINE DEFAULT CHARSET=latin1 COMMENT='ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR'
ALTER TABLE t1 MODIFY COLUMN c3 CHAR(10);
SELECT table_comment,char_length(table_comment) FROM information_schema.tables WHERE table_name='t1';
table_comment char_length(table_comment)
ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR 60
SELECT column_comment,char_length(column_comment) FROM information_schema.columns WHERE table_name='t1';
column_comment char_length(column_comment)
60
0
0
0
A 60
0
E 60
G 60
SHOW CREATE TABLE t1;
Table Create Table
t1 CREATE TABLE `t1` (
`c1` int(11) NOT NULL DEFAULT '0' COMMENT '',
`c12` int(11) DEFAULT NULL,
`c13` datetime DEFAULT NULL,
`c14` char(10) DEFAULT NULL,
`c2` int(11) DEFAULT NULL COMMENT 'A',
`c3` char(10) DEFAULT NULL,
`c4` int(11) DEFAULT NULL COMMENT 'E',
`c5` int(11) DEFAULT NULL COMMENT 'G',
PRIMARY KEY (`c1`),
KEY `c12` (`c12`,`c13`)
) ENGINE=ENGINE DEFAULT CHARSET=latin1 COMMENT='ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR'
ALTER TABLE t1 CHANGE COLUMN c4 c4_1 INTEGER COMMENT 'Ă';
SELECT table_comment,char_length(table_comment) FROM information_schema.tables WHERE table_name='t1';
table_comment char_length(table_comment)
ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR 60
SELECT column_comment,char_length(column_comment) FROM information_schema.columns WHERE table_name='t1';
column_comment char_length(column_comment)
60
0
0
0
A 60
0
Ă 10
G 60
SHOW CREATE TABLE t1;
Table Create Table
t1 CREATE TABLE `t1` (
`c1` int(11) NOT NULL DEFAULT '0' COMMENT '',
`c12` int(11) DEFAULT NULL,
`c13` datetime DEFAULT NULL,
`c14` char(10) DEFAULT NULL,
`c2` int(11) DEFAULT NULL COMMENT 'A',
`c3` char(10) DEFAULT NULL,
`c4_1` int(11) DEFAULT NULL COMMENT 'Ă',
`c5` int(11) DEFAULT NULL COMMENT 'G',
PRIMARY KEY (`c1`),
KEY `c12` (`c12`,`c13`)
) ENGINE=ENGINE DEFAULT CHARSET=latin1 COMMENT='ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR'
ALTER TABLE t1 DROP COLUMN c2;
SELECT table_comment,char_length(table_comment) FROM information_schema.tables WHERE table_name='t1';
table_comment char_length(table_comment)
ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR 60
SELECT column_comment,char_length(column_comment) FROM information_schema.columns WHERE table_name='t1';
column_comment char_length(column_comment)
60
0
0
0
0
Ă 10
G 60
SHOW CREATE TABLE t1;
Table Create Table
t1 CREATE TABLE `t1` (
`c1` int(11) NOT NULL DEFAULT '0' COMMENT '',
`c12` int(11) DEFAULT NULL,
`c13` datetime DEFAULT NULL,
`c14` char(10) DEFAULT NULL,
`c3` char(10) DEFAULT NULL,
`c4_1` int(11) DEFAULT NULL COMMENT 'Ă',
`c5` int(11) DEFAULT NULL COMMENT 'G',
PRIMARY KEY (`c1`),
KEY `c12` (`c12`,`c13`)
) ENGINE=ENGINE DEFAULT CHARSET=latin1 COMMENT='ACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPRACEGIJLNPR'
DROP TABLE t1;
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