SQL Alter table statement
Create Table
The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.
Add Columns
To add a column in a table, we will use the following syntax:
syntax:
ALTER TABLE table_name
ADD column_name datatype
ADD column_name datatype
Example:
ALTER TABLE articles
ADD author varchar(30);
ADD author varchar(30);
Delete Columns
To delete a column in a table, use the following syntax (notice that some database systems don't allow deleting a column):
syntax:
ALTER TABLE table_name
DROP COLUMN column_name
DROP COLUMN column_name
Example:
ALTER TABLE articles
DROP COLUMN author;
DROP COLUMN author;
Modify data type
To change the data type of a column in a table, use the following syntax:
syntax:
ALTER TABLE table_name
ALTER COLUMN column_name datatype
ALTER COLUMN column_name datatype
Example:
ALTER TABLE articles
ALTER COLUMN author varchar(30) ;
ALTER COLUMN author varchar(30) ;