Function for generating password MD5 on PostgreSQL

fn_password_md5.sql

/**
 * Returns the password MD5.
 * 
 * @param p_password the password string
 * @param p_salt     the salt string
 * @param p_encode   the output encoding: 'base64', 'hex', 'escape'.
 */
CREATE FUNCTION fn_password_md5(p_password VARCHAR, p_salt VARCHAR, p_encode VARCHAR) RETURNS VARCHAR AS $$
DECLARE
	v_salt_hash BYTEA := NULL;
	v_password_hash BYTEA := NULL;
	v_password_encoded VARCHAR := NULL;
BEGIN
	
	-- Generate salt hash
	SELECT DECODE(MD5(p_salt), 'hex') INTO v_salt_hash;

	-- Generate password hash using the salt hash
	SELECT DECODE(MD5(v_salt_hash || p_password::BYTEA), 'hex') INTO v_password_hash;
	
	-- Convert the password hash to hexadecimal
	SELECT ENCODE(v_password_hash, p_encode) INTO v_password_encoded;
	
	RETURN v_password_encoded;

END;
$$ LANGUAGE plpgsql;

-- EXAMPLE: 
-- select fn_password_md5('my_password', 'my_salt', 'hex');

-- EXAMPLE OUTPUT:
-- 7d3aa9f3390108c2066a2a12ef5a9b17