MySQL ALTER statement usage instance _mysql

Primary key
ALTER TABLE tablename Add new_field_id Int (5) UNSIGNED DEFAULT 0 not NULL anto_increment,add PRIMARY KEY (new_field_id);

Add a new column
Mysql>alter TABLE tablename ADD fieldname FieldType
Such as:
ALTER TABLE T2 ADD D TIMESTAMP;
ALTER TABLE infos ADD ex TINYINT not NULL DEFAULT ' 0 ';

Delete Column
Mysql>alter TABLE table_name DROP field_name
Such as:
ALTER TABLE T2 DROP COLUMN C;

Modify the original field name and type
Mysql>alter TABLE tablename Change old_field_name new_field_name field_type;
Such as:

renaming columns
ALTER TABLE T1 change a b INTEGER;

Change the type of a column
ALTER TABLE T1 change b b BIGINT not NULL;
ALTER TABLE infos change list TINYINT not NULL DEFAULT ' 0 ';

Renaming tables
ALTER TABLE T1 RENAME T2;

Add index
Mysql>alter TABLE tablename Change depno depno int (5) is not NULL;
Mysql>alter TABLE tablename ADD index index name (field name 1[, field Name 2 ...]);
Mysql>alter TABLE tablename ADD INDEX emp_name (name);

Add a search to the main keyword
Mysql>alter TABLE tablename ADD PRIMARY KEY (ID);

Index with unique restriction criteria
Mysql>alter TABLE tablename ADD UNIQUE emp_name2 (cardnumber);

Delete an index
Mysql>alter TABLE tablename DROP INDEX emp_name;