SQL Alter Table
In an earlier lesson, we created a table with the CREATE TABLE command. In this lesson, we will modify the table using the ALTER TABLE command.
Add a Column
SQL syntax
Here's the syntax for adding a column.
ALTER TABLE table_name
ADD column_name datatype;
Example SQL Statement
And here's a SQL statement that adds a column called age to the Individual table.
ALTER TABLE Individual
ADD age int;
Change the Datatype
SQL syntax
To change the data type, use ALTER COLUMN instead of ADD.
ALTER TABLE table_name
ALTER COLUMN column_name datatype;
Example SQL Statement
Here, we change the datatype of the age column to numeric.
ALTER TABLE Individual
ALTER COLUMN age numeric;
Drop a Column
"Dropping" a column means removing or deleting that column.
SQL syntax
Use DROP COLUMN followed by the name of the column you want to drop.
ALTER TABLE table_name
DROP COLUMN column_name;
Example SQL Statement
Here, we drop the age column that we added above.