PostgreSQL enum_first() Function

The PostgreSQL enum_first() function returns the first enum value of the enum type specified by the parameter.

enum_first() Syntax

Here is the syntax of the PostgreSQL enum_first() function:

enum_first(enum_value ANYENUM) -> ANYENUM

Parameters

enum_value

Required. An enumeration value. Typically, a null value is passed in.

Return value

The PostgreSQL enum_first() function returns the first enum value of the enum type specified by the parameter.

enum_first() Examples

First, let’s create an enum type my_number using the CREATE TYPE statement:

CREATE TYPE my_number AS ENUM (
    'one',
    'two',
    'three',
    'four',
    'five',
    'six',
    'seven',
    'eight',
    'nine',
    'ten'
);

Here, we created an enum type my_number, it includes ten numbers from one to ten.

Then, let’s use the PostgreSQL enum_first() function to return the first enum value of my_number:

SELECT enum_first(null::my_number);

 enum_first
------------
 one

Here, we provide a null parameter null::my_number of type my_number for the enum_first() function, and the enum_first() function returns the my_number first enum value one in .

Note that you cannot omit ::my_number in null::my_number, or PostgreSQL will give an error.

Of course, you can also pass in any enumeration value of type my_number, such as:

SELECT
    enum_first('one'::my_number),
    enum_first('two'::my_number),
    enum_first('three'::my_number),
    enum_first('four'::my_number),
    enum_first('five'::my_number),
    enum_first('six'::my_number),
    enum_first('seven'::my_number),
    enum_first('eight'::my_number),
    enum_first('nine'::my_number),
    enum_first('ten'::my_number);

-[ RECORD 1 ]---
enum_first | one
enum_first | one
enum_first | one
enum_first | one
enum_first | one
enum_first | one
enum_first | one
enum_first | one
enum_first | one
enum_first | one

Here, we pass in all enumeration values ​​of my_number type , and the enum_first() function returns the first enumeration value one in my_number.