Category: PostgreSQL

Add unique key constraint to table How to add unique key constraint to an existing table. Constraint syntax and example. Syntax ALTER TABLE table_name ADD CONSTRAINT key_name UNIQUE (column_name); Example ALTER TABLE users ADD CONSTRAINT uk_mail UNIQUE (usermail);...

Add column to existing table How to add column to existing table. Alter syntax and example Syntax ALTER TABLE table_name ADD COLUMN column_name data_type; Create table CREATE SEQUENCE seq_users INCREMENT 1 MINVALUE 1 MAXVALUE 9999999999999999 START 1 CACHE 1; CREATE TABLE...

To add multiple columns to an existing table in PostgreSQL, you can use the ALTER TABLE statement with the ADD COLUMN clause. Here’s the syntax for adding multiple columns at once: Syntax ALTER TABLE table_name ADD COLUMN column1_name data_type1, ADD COLUMN...

Drop column from existing table How to drop column from existing table. Alter syntax and example. Syntax ALTER TABLE table_name DROP COLUMN column_name RESTRICT; Create table CREATE TABLE users( userid numeric not null default nextval('seq_users'::regclass), username varchar(100), userpass varchar(250), usermail varchar(50),...

To drop multiple columns from a PostgreSQL table using the ALTER TABLE statement, you can follow these steps: Connect to your PostgreSQL database using a client or command-line interface. Syntax Execute the following ALTER TABLE statement: ALTER TABLE table_name DROP COLUMN...