New MySQL field addition field deletion field modification field cascading deletion cascade update and so on

Source: Internet
Author: User

// Primary key

alter table tabelname add new_field_id int(5) unsigned default 0 not null auto_increment ,add primary key (new_field_id);

// Delete a column

alter table t2 drop column c;

// Rename a column

alter table t1 change a b integer;

// Change the column type

alter table t1 change b b bigint not null;alter table infos change list list tinyint not null default '0';

// Rename the table

alter table t1 rename t2;

Add Index

Mysql> alter table tablename change depno int (5) not null; mysql> alter table tablename add Index name (field name 1 [, field name 2…]); Mysql> alter table tablename add index emp_name (name );

Index with primary keywords

mysql> alter table tablename add primary key(id);

Add an index with unique conditions

mysql> alter table tablename add unique emp_name2(cardnumber);

Delete An index

mysql>alter table tablename drop index emp_name;

Modify Table:

Add field:

mysql> ALTER TABLE table_name ADD field_name field_type;

Modify the original field name and type:

mysql> ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;

Delete field:

mysql> ALTER TABLE table_name DROP field_name;
Cascade update and delete (red, Case Insensitive)
DROP TABLE IF EXISTS `mail_model`;
create table mail_model(
id varchar(50) primary key not null ,
mail_filename varchar(200),

content varchar(2000)
)ENGINE=InnoDB DEFAULT CHARSET=gbk;
DROP TABLE IF EXISTS `mail_model_extend`;
create table mail_model_extend(
id int(6) auto_increment not null primary key,
rid varchar(50) not null,
content varchar(2000),
INDEX (RID),
FOREIGN KEY (RID) REFERENCES mail_model(ID) ON DELETE CASCADE ON UPDATE CASCADE
)ENGINE=InnoDB DEFAULT CHARSET=gbk;
Related Article

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.