RENAME column_name TO new_column_name Code language: SQL (Structured Query Language) ( sql )įor some reason, if you try to rename a column that does not exist, PostgreSQL will issue an error. The COLUMN keyword in the statement is optional therefore you can omit it like this: ALTER TABLE table_name Third, specify the new name for the column after the TO keyword.Second, provide name of the column that you want to rename after the RENAME COLUMN keywords.First, specify the name of the table that contains the column which you want to rename after the ALTER TABLE clause.RENAME COLUMN column_name TO new_column_name Code language: SQL (Structured Query Language) ( sql ) To rename a column of a table, you use the ALTER TABLE statement with RENAME COLUMN clause as follows: ALTER TABLE table_name Introduction to PostgreSQL RENAME COLUMN clause If we are working with a large or busy database, or we just want to have some extra assurances that we will not lose data, I prefer simply adding a new column rather than changing the type of an existing one.Summary: in this tutorial, you will learn how to use the PostgreSQL RENAME COLUMN clause in the ALTER TABLE statement to rename one or more columns of a table.

An Alternative to Changing Column Type in PostgreSQL - Adding a New Column InsteadĬhanging a column type is fairly simple, but for a large database with millions of records and a lot of concurrent queries it is also very expensive because of the ACCESS EXCLUSIVE table lock. Honestly it’s hard to know for certain if a table lock will be required by just looking through documentation.įear not, there is an alternative. These commits for not locking when increasing or removing type lengths (eg going from VARCHAR(100) to VARCHAR(255)).This commit for not locking for VARCHAR -> TEXT conversions, and any other conversions that are binary compatible.There are a few hints at exceptions in the PostgreSQL mailing lists, for example: There are some type changes that do not require a lock, but there’s no single place where these are documented (they’re not documented on the ALTER TABLE docs for example), so it’s kind of hard to tell what sort of pain your change will cause. This is crazy slow and expensive, we do not want this to happen to a production database in the middle of the day! When changing the type of a column to a type that has a different internal representation, PostgreSQL will lock the table with an ACCESS EXCLUSIVE lock in order to rewrite the whole table on disk. WARNING: PostgreSQL Column Type Changes Will Lock The Table If you do not use the USING clause, castings can fail and throw errors, like we saw above. When we use the USING clause, we provide an explicit way to transform the values. PostgreSQL will implicitly cast the common values and the constraints to the new data type if you do not use the USING clause, but this doesn’t work for all column type changes.

USING Is Not Always Required For Column Type Changes For example we could create a custom function that performs a complex operation and use this instead. While this example is fabricated, this is a foundation for much more complex and useful transformations. In this simple example we’re converting the value of the title column to be a character count for the original title using a built in PostgreSQL function.

Yum.Įxpand your database knowledge with our technical blog.ĪLTER TABLE book ALTER COLUMN title TYPE INTEGER USING ( char_length ( title )) Learn how to use Beekeeper Studio with bite-sized articles. See a list of everything Beekeeper Studio has to offer Work across multiple devices, or share your connections and queries with others. Quickly iterate on a SQL query, view and visualize results, and share with a colleague.Ī spreadsheet like interface to view, navigate, search, and edit your data.Īn easy to use no-code interface to create and alter tables, indexes, foreign keys, and more. PostgreSQL - Change The Type Of A Column, A Walkthrough With Examples | Beekeeper Studio Beekeeper Studio menuĮxperience a truly modern SQL editor that really sweats the details.

Postgresql modify column type