DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (a INT PRIMARY KEY,
b CHAR(8)
) ENGINE=xengine;
SHOW KEYS IN t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Visible	Expression
t1	0	PRIMARY	1	a	A	#	NULL	NULL		SE_SPECIFIC			YES	NULL
INSERT INTO t1 (a,b) VALUES (1,'a'),(2,'b');
INSERT INTO t1 (a,b) VALUES (1,'c');
ERROR 23000: Duplicate entry '1' for key 'PRIMARY'
DROP TABLE t1;
CREATE TABLE t1 (a INT PRIMARY KEY,
b CHAR(8) PRIMARY KEY
) ENGINE=xengine;
ERROR 42000: Multiple primary key defined
CREATE TABLE t1 (a INT,
b CHAR(8),
PRIMARY KEY (a,b)
) ENGINE=xengine;
SHOW INDEX IN t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Visible	Expression
t1	0	PRIMARY	1	a	A	#	NULL	NULL		SE_SPECIFIC			YES	NULL
t1	0	PRIMARY	2	b	A	#	NULL	NULL		SE_SPECIFIC			YES	NULL
INSERT INTO t1 (a,b) VALUES (1,'a'),(1,'b'),(2,'a'),(2,'b');
INSERT INTO t1 (a,b) VALUES (1,'b');
ERROR 23000: Duplicate entry '1-b' for key 'PRIMARY'
DROP TABLE t1;
CREATE TABLE t1 (a INT KEY,
b CHAR(8),
KEY (b)
) ENGINE=xengine;
SHOW INDEX IN t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Visible	Expression
t1	0	PRIMARY	1	a	A	#	NULL	NULL		SE_SPECIFIC			YES	NULL
t1	1	b	1	b	A	#	NULL	NULL	YES	SE_SPECIFIC			YES	NULL
DROP TABLE t1;
CREATE TABLE t1 (a INT,
b CHAR(8) PRIMARY KEY
) ENGINE=xengine;
SHOW INDEX IN t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Visible	Expression
t1	0	PRIMARY	1	b	A	#	NULL	NULL		SE_SPECIFIC			YES	NULL
ALTER TABLE t1 ADD CONSTRAINT PRIMARY KEY pk (a);
ERROR 42000: Multiple primary key defined
SHOW KEYS IN t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Visible	Expression
t1	0	PRIMARY	1	b	A	#	NULL	NULL		SE_SPECIFIC			YES	NULL
DROP TABLE t1;