drop table if exists t1,t2;
CREATE TABLE t1 (a INT, INDEX(a)) engine=innodb;
ALTER TABLE t1 RENAME TO t2, DISABLE KEYS;
Warnings:
Note	1031	Storage engine InnoDB of the table `test`.`t1` doesn't have this option
DROP TABLE t2;
CREATE TABLE t1 (
col4 text NOT NULL,
col2 int(11) NOT NULL DEFAULT '0',
col3 int(11) DEFAULT NULL,
extra int(11) DEFAULT NULL,
KEY idx (col4(10))
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
insert t1 values (repeat('1', 8193),3,1,1);
insert t1 values (repeat('3', 8193),3,1,1);
ALTER TABLE t1 ADD PRIMARY KEY (col4(10)) , ADD UNIQUE KEY uidx (col3);
ERROR 23000: Duplicate entry '1' for key 'uidx'
DROP TABLE t1;
CREATE TABLE t1 (a INT) ENGINE = InnoDB;
INSERT INTO t1 VALUES (2);
ALTER TABLE t1 ADD PRIMARY KEY (a);
ALTER TABLE t1 DROP PRIMARY KEY;
INSERT INTO t1 VALUES (2);
ALTER TABLE t1 ADD PRIMARY KEY (a);
ERROR 23000: Duplicate entry '2' for key 'PRIMARY'
DROP TABLE t1;