Vol. I · A Postgres HandbookTwelve chapters · · 756 queries

The Query & the Schema

A reading-room reference for writing PostgreSQL by hand — selects to window functions, with the schema in plain view.

IntermediateBasic SELECT

Change column data type

SQL

ALTER TABLE employees 
ALTER COLUMN contact_number TYPE VARCHAR(50);

Tested against PostgreSQL 16

Note

“Changes the data type. PostgreSQL will try to cast existing data. If implicit cast fails, you must add USING clause.