PostgreSQL Tutorial PostgreSQL Advanced PostgreSQL Database Account Management PostgreSQL References
PostgreSQL Tutorial PostgreSQL Advanced PostgreSQL Database Account Management PostgreSQL References

PostgreSQL COLUMN Keyword



ALTER COLUMN

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:

EmpIDNameCityAge
1JohnLondon25
2MarryNew York24
3JoParis27
4KimAmsterdam30

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.



DROP COLUMN

The PostgreSQL DROP COLUMN keyword is used to a delete columns from an existing table.



Syntax

The syntax for using DROP COLUMN keyword to drop columns in PostgreSQL is given below:

ALTER TABLE table_name
DROP COLUMN column_name;

Example:

Consider a database table called Employee with the following records:

EmpIDNameCityAge
1JohnLondon25
2MarryNew York24
3JoParis27
4KimAmsterdam30

To drop the Salary column from the Employee table, the following statement can be used:

ALTER TABLE Employee
DROP COLUMN Age;

This will produce the below mentioned result:

EmpIDNameCity
1JohnLondon
2MarryNew York
3JoParis
4KimAmsterdam

❮ PostgreSQL Keywords