Typical use of alter statements in mysql

ADD a field in the classic usage of the alter statement in mysql: alter table table_name ADD field_name field_type; www.2cto.com modify the original field name and type: alter table table_name CHANGE old_field_name new_field_name field_type; Delete the field: alter table table_name DROP field_name example change to auto-increment alter table tb_name modify id int auto_increment primary key modify Field default value alter table tablename alter column drop default; (if the default value exists, delete it first) alter table tablename alter column set default 'T5 '; (if it does not exist, you can directly set it) add the primary key alter table tabelname add new_field_id int (5) unsigned default 0 not null auto_increment, add primary key (new_field_id ); add a new alter table t2 add d timestamp to www.2cto.com; alter table infos add ex tinyint not null default '0'; Delete the alter table t2 drop column c; rename the alter table t1 change a B integer; change the column type alter table t1 change B bigint not null; alter table infos change li St list tinyint not null default '0'; rename alter table t1 rename t2; www.2cto.com add index alter table tablename add index name (field name 1 [, field name 2…]); Alter table tablename add index emp_name (name); add the index alter table tablename add primary key (id) with the primary keyword ); add the index alter table tablename add unique emp_name2 (cardnumber) with the unique restrictions; delete an index 5 alter table tablename drop index emp_name;