例子1，不带returns :

[postgres@cnrd56 bin]$ ./psqlpsql (9.1.2)Type "help" for help.postgres=# CREATE FUNCTION sales_tax(subtotal real, OUT tax real) AS $$postgres$# BEGINpostgres$#     tax := subtotal * 0.06;postgres$# END;postgres$# $$ LANGUAGE plpgsql;CREATE FUNCTIONpostgres=# postgres=# select sales_tax(100); sales_tax -----------         6(1 row)

例子2，带returns：

[postgres@cnrd56 bin]$ ./psqlpsql (9.1.2)Type "help" for help.postgres=# CREATE FUNCTION sales_tax2(subtotal real, OUT tax real) returns real AS $$postgres$# BEGINpostgres$#     tax := subtotal * 0.06;postgres$# END;postgres$# $$ LANGUAGE plpgsql;CREATE FUNCTIONpostgres=# postgres=# select sales_tax2(100); sales_tax2 ------------          6(1 row)postgres=#