How to find table names having ID (primary key) of a certain value in a hierarchy of tables? - sql

Question

I use Oracle 11g and have a massive number of tables representing inheritance, where a base parent table has a primary key NUMBER ID. The subsequent tables inherit from it, representing through the shared primary key NUMBER ID. Let's assume there is a multiple layers of such inheritance.
To have a clear picture, let's work with the following simplified structure and assume the hierarchy is quite complex:
- TABLE FOOD
- TABLE FRUIT
- TABLE CYTRUS
- TABLE ORANGE
- TABLE GREPFRUIT
- TABLE VEGETABLE
- TABLE MEAT
- TABLE BEEF
- TABLE SIRLOIN
- TABLE RIB EYE
- TABLE CHICKEN
This is not taxative, regardless of how dumb the example is, assume such a multi-layered hierarchy using Class Table Inheritance (aka Table Per Type Inheritance).
If you want to insert a record to a table ORANGE having a certain generated ID, there must be inserted records to the parent tables (CYTRUS, FRUIT and FOOD) as well. Assume an ORM engine takes care after this as keeping such consistency would be very complex.
Let's also assume each of the tables in the hierarchy ends with a certain word (let's say FOOD: FRUIT_FOOD, CYTRUS_FOOD etc.) - I didn't include it to the chart above for sake of clarity.
Question: I have found a record in FOOD table with ID = 123 based on certain criteria. Thanks to the hierarchical structure, how do I find what tables contain the record with the very same ID using SQL only? I.e. my goal is to find out what * the lowest type in the hierarchy* the certain ID is related to.
Note: If you have also an answer for a newer version of Oracle, don't hesitate to include it as long as others might find it useful.

Answer 1

Assuming all these tables have a column ID but you may adjust based on the example.
Q1. what tables contain the record with the very same ID using SQL only
You could use a series unions to determine this eg.
SELECT
id,
table_type,
heirarchy_level
FROM (
SELECT ID, 'FOOD', 1 FROM FOOD
UNION ALL
SELECT ID,'FRUIT',2 FROM FRUIT
UNION ALL
SELECT ID,'CYTRUS',3 FROM CYTRUS
UNION ALL
SELECT ID,'ORANGE',4 FROM ORANGE
UNION ALL
SELECT ID,'GREPFRUIT',4 FROM GREPFRUIT
UNION ALL
SELECT ID,'VEGETABLE',2 FROM VEGETABLE
UNION ALL
SELECT ID,'MEAT',2 FROM MEAT
UNION ALL
SELECT ID,'BEEF',3 FROM BEEF
UNION ALL
SELECT ID,'SIRLOIN',4 FROM SIRLOIN
UNION ALL
SELECT ID,'RIBEYE',4 FROM RIBEYE
UNION ALL
SELECT ID,'CHICKEN',3 FROM CHICKEN
) t
WHERE
id = 123
This would return a table with the id=123 but more importantly a table listing all tables where the record was present along with the depth/level in the hierarchy. You could then use MAX or order by to determine the deepest level
Q2. what is the lowest type in the hierarchy the certain ID is related to
This would return only one record with the lowest type
SELECT
id,
table_type,
heirarchy_level
FROM (
SELECT ID, 'FOOD', 1 FROM FOOD
UNION ALL
SELECT ID,'FRUIT',2 FROM FRUIT
UNION ALL
SELECT ID,'CYTRUS',3 FROM CYTRUS
UNION ALL
SELECT ID,'ORANGE',4 FROM ORANGE
UNION ALL
SELECT ID,'GREPFRUIT',4 FROM GREPFRUIT
UNION ALL
SELECT ID,'VEGETABLE',2 FROM VEGETABLE
UNION ALL
SELECT ID,'MEAT',2 FROM MEAT
UNION ALL
SELECT ID,'BEEF',3 FROM BEEF
UNION ALL
SELECT ID,'SIRLOIN',4 FROM SIRLOIN
UNION ALL
SELECT ID,'RIBEYE',4 FROM RIBEYE
UNION ALL
SELECT ID,'CHICKEN',3 FROM CHICKEN
) t
WHERE
id = 123
ORDER BY
heirarchy_level desc
LIMIT 1