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The PostgreSQL 9.0 Reference Manual - Volume 2 - Programming Guide
by The PostgreSQL Global Development Group
Paperback (6"x9"), 478 pages
ISBN 9781906966065
RRP £14.95 ($19.95)

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9.1.2 Supported Argument and Result Data Types

Functions written in PL/pgSQL can accept as arguments any scalar or array data type supported by the server, and they can return a result of any of these types. They can also accept or return any composite type (row type) specified by name. It is also possible to declare a PL/pgSQL function as returning record, which means that the result is a row type whose columns are determined by specification in the calling query, as discussed in Volume 1A: Table Functions.

PL/pgSQL functions can be declared to accept a variable number of arguments by using the VARIADIC marker. This works exactly the same way as for SQL functions, as discussed in section 5.4.5 SQL Functions with Variable Numbers of Arguments.

PL/pgSQL functions can also be declared to accept and return the polymorphic types anyelement, anyarray, anynonarray, and anyenum. The actual data types handled by a polymorphic function can vary from call to call, as discussed in section 5.2.5 Polymorphic Types. An example is shown in section 9.3.1 Declaring Function Parameters.

PL/pgSQL functions can also be declared to return a “set” (or table) of any data type that can be returned as a single instance. Such a function generates its output by executing RETURN NEXT for each desired element of the result set, or by using RETURN QUERY to output the result of evaluating a query.

Finally, a PL/pgSQL function can be declared to return void if it has no useful return value.

PL/pgSQL functions can also be declared with output parameters in place of an explicit specification of the return type. This does not add any fundamental capability to the language, but it is often convenient, especially for returning multiple values. The RETURNS TABLE notation can also be used in place of RETURNS SETOF.

Specific examples appear in section 9.3.1 Declaring Function Parameters and section 9.6.1 Returning From a Function.

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