MySQL Learning (MU lesson note 7) Modify data sheet (bottom)

Add a PRIMARY KEY constraint

ALTER TABLE tb1_name ADD [CONSTRAINT [symbol]] PRIMARY KEY [Index_type] (Index_col_name,.......)

ALTER TABLE user2 ADD CONSTRAINT pk_user2_id PRIMARY KEY (ID);

Add a UNIQUE Constraint

ALTER TABLE user2 ADD UNIQUE (username);

Add a DEFAULT constraint add, alter

Alter TABLE User2 ALTER age SET DEFAULT 15;

Delete primary key Drop '

ALTER TABLE user2 DROP PRIMARY KEY;

Remove UNIQUE Constraint

Show UNIQUE constraint show indexes from User2\g; (Rendered in grid form)

Modifying a column definition Modify

ALTER TABLE user2 MODIFY pid VARCHAR (a) first;

Modify column name change can modify name, type, and definition (almighty)

ALTER TABLE user2 Change pid p_id SMALLINT UNSIGNED;

Modify Table name Rename

ALTER TABLE user2 RENAME user3;

Method 2:rename table User3 to User2;

Modify table names, column names as few as possible

MySQL Learning (MU lesson note 7) Modify data sheet (bottom)