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PostgreSQL 9 Administration Cookbook - Second Edition by Simon Riggs, Gianni Ciolli, Hannu Krosing, Gabriele Bartolini

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Changing the definition of a data type

PostgreSQL comes with several data types, but users can create custom types to most faithfully represent any value. Data type management is mostly, but not exclusively, a developer's job, and data type design goes beyond the scope of this book. This is a quick recipe that covers only the simpler problem of the need to apply a specific change to an existing data type.

Getting ready

Enumerative data types are defined like this:

CREATE TYPE cookbook_author AS ENUM ('Hannu','Simon');

The other popular case is composite data types, which are created in this way:

CREATE TYPE node AS (
  node_name text,
  connstr text,
  standbys text[]);

How to do it…

Say you are upgrading your database to edition, or version, 2.0 and ...

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