So here I am and need to see some results from a MYSQL database based not on one but on results from a few tables.
TABLE DESCRIPTION:
Metaexplanation:
Tablename
Row1,Row2,Row3....Row(N)
Tables:
---------------
|table toy |
------------------------------
|toy_id | name | description |
------------------------------
--------------------
|table owned_toy |
----------------------------
| owner | toy_id |
----------------------------
--------------------
|table toy_expansions |
-------------------------------
| expansion | toy_id |
-------------------------------
I created a query to identify toys with no owner assigned
SELECT DISTINCT * from toy WHERE NOT EXISTS (SELECT * FROM ownedtoy WHERE owned_toy.toy_id = toy.id);
That worked and I was able to identify things that had no owner.
Now to make things more interesting I am trying to find out a way to discover how many expansions exist for each of the toys that I have identified in the query above.
I can count the total number of expansions to the toys using:
Select COUNT(expansion) from toy_expansions;
However what I need is to see the total number of expansions for each DISTINCT toy that does not yet have an owner, and it needs to be sorted so that I see the results from the first query c开发者_如何学Combined with a column saying "number of Expansions" that lists the number of expansions for each toy identified to have no owner
I would like to be able to adding the results by combining the original query with a statement like this:
Select COUNT(expansion) as "Number of expansions" from toy_expansions
Also just to make it a little more difficult I would like to be able to execute it in one single query without creating extra tables etc. i.e. without making any changes to the db itself.
Any ideas ?
SELECT t.name, COUNT(te.expansion) AS NumberOfExpansions
FROM toy t
LEFT JOIN toy_expansions te
ON t.id = te.toy_id
LEFT JOIN owned_toy ot
ON t.id = ot.toy_id
WHERE ot.toy_id IS NULL
GROUP BY t.name
精彩评论