How to create a "hard-coded" small SQL join table in code? - sql

Question

Context: I do not have the ability to create/update/edit the tables in question.
I have two tables that I am trying to join via a manual SQL query in Tableau. There exists a column in each table I can use to link the tables together, but I need a third table (that does not exist) to link them.
There are only 6 values I'd like to link, I was hoping there is some way to declare an "in-memory" table or similar in SQL to join these tables.
For example - I'd like to join these two tables together:
Table 1
name
value
place 1
14
place 2
10
place 3
100
Table 2
identifier
property
superstore
awesome
hospital
bad
port
great
Can I somehow hard-code the following "table" into SQL code to join them?
hard coded table
name
identifier
place 1
hospital
place 2
port
place 3
superstore
Should yield the following:
name
identifier
value
property
place 1
hospital
14
bad
place 2
port
10
great
place 3
superstore
100
awesome
If I could create a new table with the linkage above I would, but I can't.
If it's relevant - this is using an Oracle database.
Thank you for your help!

Answer 1

You can use SELECT ... FROM DUAL and UNION ALL to create the data.
It can go in a sub-query factoring (WITH) clause:
WITH hard_coded_table ( name, identifier ) AS (
SELECT 'place 1', 'hospital' FROM DUAL UNION ALL
SELECT 'place 2', 'port' FROM DUAL UNION ALL
SELECT 'place 3', 'superstore' FROM DUAL
)
SELECT t1.*,
t2.*
FROM Table1 t1
INNER JOIN hard_coded_table h
ON ( t1.name = h.name )
INNER JOIN table2 t2
ON ( t2.identifier = h.identifier );
Or just as a sub-query:
SELECT t1.*,
t2.*
FROM Table1 t1
INNER JOIN (
SELECT 'place 1' AS name, 'hospital' AS identifier FROM DUAL UNION ALL
SELECT 'place 2', 'port' FROM DUAL UNION ALL
SELECT 'place 3', 'superstore' FROM DUAL
) h
ON ( t1.name = h.name )
INNER JOIN table2 t2
ON ( t2.identifier = h.identifier );
Which, for your sample data:
CREATE TABLE Table1 ( name, value ) AS
SELECT 'place 1', 14 FROM DUAL UNION ALL
SELECT 'place 2', 10 FROM DUAL UNION ALL
SELECT 'place 3', 100 FROM DUAL;
CREATE TABLE Table2 ( identifier, property ) AS
SELECT 'superstore', 'awesome' FROM DUAL UNION ALL
SELECT 'hospital', 'bad' FROM DUAL UNION ALL
SELECT 'port', 'great' FROM DUAL;
Both output:
NAME | VALUE | IDENTIFIER | PROPERTY
:------ | ----: | :--------- | :-------
place 3 | 100 | superstore | awesome
place 1 | 14 | hospital | bad
place 2 | 10 | port | great
db<>fiddle here