CREATE TABLE t1(a INT, b INT);
CREATE INDEX IF NOT EXISTS i1 ON t1(a);
SHOW CREATE TABLE t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` int(11) DEFAULT NULL,
  `b` int(11) DEFAULT NULL,
  KEY `i1` (`a`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
DROP INDEX IF EXISTS i1 ON t1;
SHOW CREATE TABLE t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` int(11) DEFAULT NULL,
  `b` int(11) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
DROP INDEX IF EXISTS i1 ON t1;
Warnings:
Note	1091	Can't DROP INDEX `i1`; check that it exists
SHOW CREATE TABLE t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` int(11) DEFAULT NULL,
  `b` int(11) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
CREATE OR REPLACE INDEX i1 ON t1(a);
SHOW CREATE TABLE t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` int(11) DEFAULT NULL,
  `b` int(11) DEFAULT NULL,
  KEY `i1` (`a`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
CREATE OR REPLACE INDEX i1 ON t1(a,b);
SHOW CREATE TABLE t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` int(11) DEFAULT NULL,
  `b` int(11) DEFAULT NULL,
  KEY `i1` (`a`,`b`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
DROP TABLE t1;
CREATE OR REPLACE INDEX IF NOT EXISTS i1 ON t1(b,a);
ERROR HY000: Incorrect usage of OR REPLACE and IF NOT EXISTS