CODEWITHSUNDEEP
sqloracle-databasehierarchical-datarecursive-query
Seth Duncan
Seth Duncan

Reputation: 1255

Recursive Oracle query

I have three tables:

I need to pass in a query with multiple options and a subscription ID, something along these lines:

SELECT optionid, optionvalue WHERE subscriptionid = x AND options IN (a, b, c, d, e, f)

Only I need to implement the inherits by logic via a recursive call like this:

if subscriptionoption exists for subscription id & optionid
    use subscriptionoption.optionvalue in the row
else
    if inherits is not NULL
        call this function using inherited subscription id
    else
        use options.optiondefaultvalue for that optionid

Upvotes: 1

Views: 1779

Answers (1)

Dave Costa
Dave Costa

Reputation: 48111

To do it in SQL, I think you need to incorporate a hierarchical query. Here's a swing at it, but I haven't been able to test it out.

SELECT optionID, NVL( MAX(optionValue), MAX(optionDefaultValue) ) optionValue
FROM (SELECT optionID, optionDefaultValue, subscriptionID, inherits
        FROM options CROSS JOIN subscriptions
        WHERE optionID IN (a,b,c,d,e,f)
     )
     LEFT JOIN subscriptionOptions USING (optionId, subscriptionID)
START WITH subscriptionID = x
CONNECT BY PRIOR optionValue IS NULL
       AND subscriptionID = PRIOR inherits
       AND optionID = PRIOR optionID
GROUP BY optionID

Another approach would be to write a function that implements the recursive logic for a single subscriptionID and optionID, then call it like this:

SELECT optionID, NVL( getSubscriptionOption( x, optionID), optionDefaultValue )
  FROM options
  WHERE optionID IN (a,b,c,d,e,f)

The function could be something like:

FUNCTION getSubscriptionOption( pSubID NUMBER, pOptID NUMBER )
  RETURN subscriptionOptions.optionValue%TYPE
  IS
    l_optionValue subscriptionOptions.optionValue%TYPE;
    l_inherits    subscriptionOptions.inherits%TYPE;
  BEGIN
    SELECT optionValue
      INTO l_optionValue
      FROM subscriptionOptions
      WHERE subscriptionID = pSubID
        AND optionID = pOptID;
    RETURN l_optionValue;
  EXCEPTION
    WHEN no_data_found THEN
      SELECT inherits
        INTO l_inherits
        FROM subscriptions
        WHERE subscriptionID = pSubID;
      IF inherits IS NULL THEN
        RETURN NULL;
      ELSE
        RETURN getSubscriptionOption( l_inherits, pOptID );
      END IF;
  END;

or could be written to use a loop instead of recursion.

Upvotes: 1

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