PostgreSQL ALTER COLUMN Keyword
The PostgreSQL ALTER COLUMN keyword is used to change the data type of a column in an existing table.
Syntax
The syntax for using ALTER COLUMN statement to modify datatype of a column in PostgreSQL is given below:
ALTER TABLE table_name ALTER COLUMN column_name TYPE datatype;
Example:
Consider a database table called Employee with the following records:
| EmpID | Name | City | Age |
|---|---|---|---|
| 1 | John | London | 25 |
| 2 | Marry | New York | 24 |
| 3 | Jo | Paris | 27 |
| 4 | Kim | Amsterdam | 30 |
In this table, the datatype of City column is VARCHAR(100). To change the datatype of the column to VARCHAR(255), the statement is given below:
ALTER TABLE Employee ALTER COLUMN City TYPE VARCHAR(255);
This will change the datatype of City column from VARCHAR(100) to VARCHAR(255). For a complete reference of all the data types available in PostgreSQL, see Data Types reference.
❮ PostgreSQL Keywords
