MySQL alter statement usage

Some syntaxes add fields: ALTERTABLEtable_nameADDfield_namefield_type; modify the original field name and type: ALTERTABLEtable_nameCHANGE

Some syntaxes ADD fields: alter table table_name ADD field_name field_type; modify the original field name and type: alter table table_name CHANGE

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MySQL alter statement usage

[Date: 2012-09-10] Source: Linux community Author: yucan1001 [Font:]

Some syntaxes

Add field:

Alter table table_name ADD field_name field_type;

Modify the original field name and type:
Alter table table_name CHANGE old_field_name new_field_name field_type;

Delete 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 '; (you can set it directly if it does not exist)

Add 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 column
Alter table t2 add d timestamp;
Alter table infos add ex tinyint not null default '0 ';

Delete column
Alter table t2 drop column c;

Rename a column
Alter table t1 change a B integer;

Change column type
Alter table t1 change B bigint not null;
Alter table infos change list tinyint not null default '0 ';

Rename a table
Alter table t1 rename t2;

Add Index
Alter table tablename add index name (field name 1 [, field name 2…]);
Alter table tablename add index emp_name (name );

Index with primary keywords
Alter table tablename add primary key (id );

Add an index with unique conditions
Alter table tablename add unique emp_name2 (cardnumber );

Delete An index 5
Alter table tablename drop index emp_name;

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