Add and delete fields in MySQL

How can I add fields to MySQL? This is a problem that many new users have just mentioned. The following describes how to add and delete fields in MySQL.

Add a MySQL field:

 
 

  
  
Alter table 'user _ movement_log'
  
  
Add column GatewayId int not null default 0 AFTER 'regionid' (AFTER which field is added)
  
  
 
 
 

Delete field:

 
 

  
  
alter table `user_movement_log` drop column Gatewayid  
  
  
 
 
 

Adjust the field order:

 
 

  
  
Alter table 'user _ movement_log 'CHANGE 'gatewayid' int not null default 0 AFTER RegionID
  
  
 
  
  
// 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 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 bigint not null;
  
  
Alter table infos change list tinyint not null default '0 ';
  
  
// Rename the table
  
  
 
  
  
Alter table t1 rename t2; add an 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); add the index with the primary keyword
  
  
 
  
  
Mysql> alter table tablename add primary key (id); add an index with unique restrictions
  
  
 
  
  
Mysql> alter table tablename add unique emp_name2 (cardnumber); delete an index
  
  
 
  
  
Mysql> alter table tablename drop index emp_name; modify the 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 a field:
  
  
 
  
  
Mysql> alter table table_name DROP field_name;
 
 

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