CHANGE COLUMN IF EXISTS does not change the existing column and throws a warning that the column does not exist:
MariaDB [test]> create table t1 (a int);
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Query OK, 0 rows affected (0.20 sec)
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MariaDB [test]> alter table t1 change column a b bigint;
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Query OK, 0 rows affected (0.45 sec)
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Records: 0 Duplicates: 0 Warnings: 0
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MariaDB [test]> drop table t1;
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Query OK, 0 rows affected (0.10 sec)
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MariaDB [test]> create table t1 (a int);
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Query OK, 0 rows affected (0.24 sec)
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MariaDB [test]> alter table t1 change column if exists a b bigint;
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Query OK, 0 rows affected, 1 warning (0.00 sec)
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Records: 0 Duplicates: 0 Warnings: 1
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MariaDB [test]> show warnings;
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+-------+------+----------------------------+
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| Level | Code | Message |
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+-------+------+----------------------------+
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| Note | 1054 | Unknown column 'a' in 't1' |
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+-------+------+----------------------------+
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1 row in set (0.01 sec)
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MariaDB [test]> show create table t1;
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+-------+---------------------------------------------------------------------------------------+
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| Table | Create Table |
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+-------+---------------------------------------------------------------------------------------+
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| t1 | CREATE TABLE `t1` (
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`a` int(11) DEFAULT NULL
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) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
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+-------+---------------------------------------------------------------------------------------+
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1 row in set (0.00 sec)
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Without IF EXISTS clause it works all right:
MariaDB [test]> alter table t1 change column a b bigint;
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Query OK, 0 rows affected (0.47 sec)
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Records: 0 Duplicates: 0 Warnings: 0
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MariaDB [test]> show create table t1;
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+-------+------------------------------------------------------------------------------------------+
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| Table | Create Table |
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+-------+------------------------------------------------------------------------------------------+
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| t1 | CREATE TABLE `t1` (
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`b` bigint(20) DEFAULT NULL
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) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
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+-------+------------------------------------------------------------------------------------------+
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1 row in set (0.01 sec)
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Test case:
create table t1 (a int);
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alter table t1 change column if exists a b bigint;
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show warnings;
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show create table t1;
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revision-id: bar@mariadb.org-20130424142022-u4xhikvoqggze9b0
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revno: 3745
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branch-nick: 10.0
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Bug
Major
MDEV-318 IF (NOT) EXIST clauses for ALTER TABLE (MWL #252)
