Using SQL Case in a UNION SELECT to combine two tables with no like fields

Question

I have two SQL tables (that cannot be modified, this is a question of how to get it without like columns), and I need to find out the table type when using an inner join to list the city and states:

CREATE TABLE authors 
  ( 
  au_id    CHAR(3)     NOT NULL, 
  au_fname VARCHAR(15) NOT NULL, 
  au_lname VARCHAR(15) NOT NULL, 
  phone    VARCHAR(12)         , 
  address  VARCHAR(20)         , 
  city     VARCHAR(15)         , 
  state    CHAR(2)             , 
  zip      CHAR(5)             , 
  CONSTRAINT pk_authors PRIMARY KEY (au_id) 
  ); 

CREATE TABLE publishers 
  ( 
  pub_id   CHAR(3)     NOT NULL, 
  pub_name VARCHAR(20) NOT NULL, 
  city     VARCHAR(15) NOT NULL, 
  state    CHAR(2)             , 
  country  VARCHAR(15) NOT NULL, 
  CONSTRAINT pk_publishers PRIMARY KEY (pub_id) 
  ); 

I am attempting to use a CASE for the select to output correctly:

SELECT CASE
    WHEN LCASE(SUBSTR(/*suppose id*/, 0, 1)) == 'a'
    THEN 'author'
    ELSE 'publisher'
    END
AS type, city, state
FROM authors
INNER JOIN publishers

The tables are in a format such that the id's are different, but also hold different names:

INSERT INTO authors VALUES('A01','Sarah','Buchman','718-496-7223', 
      '75 West 205 St','Bronx','NY','10468'); 
INSERT INTO publishers VALUES('P01','Abatis Publishers','New York','NY','USA'); 

And I'm attempting to reach an output like so:

type        |   city        |   state
--------------------------------------------------
author      |   Rochester   |   NY
author      |   Syracuse    |   NY
publisher   |   New York    |   NY

How can I effectively make a comparison between the two tables when they do not have like columns? Can I call a field value on a table to check if it is null without throwing an SQL Exception?

Answer 1

As there is no column to make a comparison between the two tables ie, nothing which can filter out the rows after Cartesian product, inner join won't server the purpose. It's more of like selecting records from two multi-sets and combining them. In T-SQL this can be achieved using Union as:

select 'authors' as [type]
       , city,state
       from authors
union 
select 'publishers' as [type]
       , city,state
       from publishers