Alter alter the name of the table alter the name of the table structure to increase the column
alter table statement The alter table statement is used to add, modify, or delete columns from an existing table.
sql alter table syntax To add columns to the table, use the following syntax:
alter table table_name add column_name datatype To delete a column in a table, use the following syntax:
alter table table_name drop column column_name Note: Some database tutorial systems do not allow this way of dropping columns in database tables (drop column column_name).
To change the data type of a column in a table, use the following syntax:
alter table table_name alter column column_name datatype
Look at the alert detailed syntax
alter_specification: add [column] create_definition [first | after column_name] or add index [index_name] (index_col_name, ...) or add primary key (index_col_name, ...) or add unique [index_name] (index_col_name, ...) or alter [column] col_name {set default literal | drop default} or change [column] old_col_name create_definition or modify [column] create_definition or drop [column] col_name or drop primary key or drop index index_name or rename [as] new_tbl_name or table_options eg:
Modify the database structure: Increase the field:
alter table dbname add column <field name> <field option>
Modify fields:
alter table dbname change <old field name> <new field name> <option>
Delete field: alter table dbname drop column <field name>
Example operation:
> create database office;
> use office;
mysql> create table personal (
-> member_no char (5) not null,
-> name char (,
-> birthday date,
-> exam_score tinyint,
-> primary key (member_no)
->);
query ok, 0 rows affected (0.01 sec)
Take a look at the examples
mysql> alter table topics change hotico hot_count int (4);
mysql> alter table topics alter hot_count set default 1;
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