Basic MySQL commands

++ ++ Basic MySQL Operations <br/> // primary key 549830479 <br/> alter table tabelname add new_field_id int (5) unsigned default 0 not null auto_increment, add primary key (new_field_id); <br/> // Add a new column 549830479 <br/> alter table T2 add D timestamp; <br/> alter table Infos add ex tinyint not null default '0'; <br/> // delete column 549830479 <br/> alter table T2 drop column C; <br/> // Rename column 549830479 <br/> alter table T1 change a B integer; <br/> // change column type 549830479 <br/> alter table T1 change B bigint not null; <br/> alter table Infos change list tinyint not null default '0'; <br/> // rename table 549830479 <br/> alter table T1 rename T2; <br/> Add an index 549830479 <br/> mysql> alter table tablename change depno int (5) not null; <br/> mysql> alter table tablename add Index name (field name 1 [, field name 2... ]); <Br/> mysql> alter table tablename add index emp_name (name ); <br/> index 549830479 with primary keywords <br/> mysql> alter table tablename add primary key (ID ); <br/> Add the index with the unique condition 549830479 <br/> mysql> alter table tablename add unique emp_name2 (cardNumber ); <br/> delete an index 549830479 <br/> mysql> alter table tablename drop index emp_name; <br/> Modify Table 549830479 <br/> Add a field: 549830479 <br/> mysql> alter table table_name add field_name field_type; <br/> modify the original field name and type: 549830479 <br/> mysql> alter table table_name change old_field_name new_field_name field_type; <br/> Delete field: 549830479 <br/> mysql> alter table table_name drop field_name; </P> <p> ++ +++ ++ MySQL constraints <br/> -------- Add a primary key constraint (bookid as the primary key) <br/> alter table bookmessage <br/> Add constraint pk_bookid primary key (bookid) <br/> -------- Add a unique constraint <br/> alter table bookmessage <br/> Add constraint uq_bookid unique (bookid) <br/> --------- add default constraint <br/> alter table bookmessage <br/> Add constraint df_address defauit ('address unknown ') for address <br/> -------- add check constraint. The age must be between 15---40. <br/> alter table readermessage <br/> Add constraint ck_age check (age between 15 and 40) <br/> ------- Add a foreign key constraint <br/> alter table bookmessage <br/> Add constraint fk_bookid <br/> foreign key (bookid) <foreign key> references readermessage <Table> (readerid) <primary key in the table> <br/> ------- Delete constraint <br/> alter table table name <br/> drop constraint name <br/> ++ ++ ++ <br/>