Postgres function return table with extra column

Question

Newbie to Postgres here..

I have a Postgres / plpgsql function that will return a table. I want to return everything from a query plus a logical value that I create and return along with it.

However, after searching around I can't seem to figure out how I can return this data along with a logical value that I generate on the fly within the query?

CREATE OR REPLACE FUNCTION public.sp_user_get_credentials_by_email(email_address character varying)
RETURNS TABLE(credential_id integer, user_id integer, password_hash character varying, password_salt character varying, created_at timestamp without time zone, last_updated_at timestamp without time zone, logical_value_return SMALLINT)
 LANGUAGE plpgsql
AS $function$

DECLARE
sproc_logical_value_return SMALLINT;

BEGIN

-- also want to return logical_value_return along with the query below
-- ex: sproc_logical_value_return = (2)::INT2; how do I add this as a column logical_value_return along with the query below?

  RETURN QUERY
    SELECT
      myapp_users_credentials.credential_id,
      myapp_users_credentials.user_id,
      myapp_users_credentials.password_hash,
      myapp_users_credentials.password_salt,
      myapp_users_credentials.created_at,
      myapp_users_credentials.last_updated_at
    FROM
      myapp_users_credentials
    JOIN myapp_contacts_assoc ON
      myapp_contacts_assoc.user_id = myapp_users_credentials.user_id AND
      myapp_users_credentials.expired_at IS NULL
    JOIN myapp_contacts ON
      myapp_contacts.contact_id = myapp_contacts_assoc.contact_id AND
      myapp_users_credentials.expired_at IS NULL
    WHERE
      myapp_contacts.value = $1 AND
      myapp_contacts.type = 1 AND
      myapp_contacts.is_primary = 1
    LIMIT 1;

  IF NOT FOUND THEN
    RAISE EXCEPTION 'Credentials not found';
  END IF;

END
$function$

Answer 1

Just add the variable to the SELECT list:

CREATE OR REPLACE FUNCTION public.sp_user_get_credentials_by_email(email_address varchar)
  RETURNS TABLE (credential_id integer
               , user_id integer
               , password_hash varchar
               , password_salt varchar
               , created_at timestamp
               , last_updated_at timestamp
               , logical_value_return smallint)
  LANGUAGE plpgsql ROWS 1 AS
$func$
DECLARE
   sproc_logical_value_return SMALLINT := 2;  -- you can assign at declaration time
BEGIN
   RETURN QUERY
      SELECT uc.credential_id,
             uc.user_id,
             uc.password_hash,
             uc.password_salt,
             uc.created_at,
             uc.last_updated_at
             sproc_logical_value_return  -- just put it in the SELECT list
      FROM   myapp_users_credentials uc
      JOIN   myapp_contacts_assoc    ca ON ca.user_id = uc.user_id      AND uc.expired_at IS NULL
      JOIN   myapp_contacts          c  ON c.contact_id = ca.contact_id AND uc.expired_at IS NULL
      WHERE  c.value = $1
      AND    c.type  = 1
      AND    c.is_primary = 1
      LIMIT  1;

   IF NOT FOUND THEN
      RAISE EXCEPTION 'Credentials not found';
   END IF;
END
$func$;

I simplified with table aliases.

Since your function returns a single row by definition, the value is also returned only once.

I would use RETURNS RECORD combined with OUT parameters instead of RETURNS TABLE since you return exactly 1 row anyway.

CREATE OR REPLACE FUNCTION public.sp_user_get_credentials_by_email(
                 IN  email_address varchar
               , OUT credential_id integer
               , OUT user_id integer
               , OUT password_hash varchar
               , OUT password_salt varchar
               , OUT created_at timestamp
               , OUT last_updated_at timestamp
               , OUT logical_value_return smallint)
  LANGUAGE plpgsql AS
$func$
BEGIN
   logical_value_return := 2;  -- assign separately or with SELECT list

   SELECT uc.credential_id, uc.user_id, uc.password_hash, uc.password_salt, uc.created_at, uc.last_updated_at
   INTO      credential_id,    user_id,    password_hash,    password_salt,    created_at,    last_updated_at
   FROM   myapp_users_credentials uc
   JOIN   myapp_contacts_assoc    ca ON ca.user_id = uc.user_id      AND uc.expired_at IS NULL
   JOIN   myapp_contacts          c  ON c.contact_id = ca.contact_id AND uc.expired_at IS NULL
   WHERE  c.value = $1
   AND    c.type = 1
   AND    c.is_primary = 1
   LIMIT  1;

   IF NOT FOUND THEN
      RAISE EXCEPTION 'Credentials not found';
   END IF;
END
$func$;

RETURNS RECORD is redundant noise which can be omitted in this case.

The subtle difference: You can still return the logical constant, even when no row is found. Other columns would be NULL in this case. Details:

• Return multiple fields as a record in PostgreSQL with PL/pgSQL
• Declaring the tuple structure of a record in PL/pgSQL