inner-join

I have three tables: COLLECTION PERSON PERSON_COLLECTION where PERSON_COLLECTION is a mapping table id|person_id|collection_id I now want to select all entries in collection and order them by person.name . Do I have to join the separate tables with the mapping table first and then do a join again on the results? SELECT c.*, p.Name FROM Collection c JOIN Person_Collection pc ON pc.collection_id = c.id JOIN Person p ON p.id = pc.person_id ORDER BY p.Name The order you join won't break it but depending on which sql product you're using may effect performance. You need to decide if you want ALL

I have a table of metals MetalID integer MetalName text MetalCode text Item table ItemID integer ItemName text ... Metal1 int Ref.-> metals.metalID Metal2 int Ref.-> metals.metalID Metal3 int Ref.-> metals.metalID I am trying to select three MetalCodes SELECT m.MetalCode as 'Metal1', m.MetalCode as 'Metal2',m.MetalCode as 'Metal3' FROM Item as k INNER JOIN Metals AS m ON m.metalID=k.metal1 INNER JOIN Metals AS m ON m.metalID=k.metal2 INNER JOIN Metals AS m ON m.metalID=k.metal3 WHERE k.ItemID=? Looks like I am doing it completely wrong. Please, help. You should specify different aliases for

So... which one is faster (NULl value is not an issue), and are indexed. SELECT * FROM A JOIN B b ON b.id = a.id JOIN C c ON c.id = b.id WHERE A.id = '12345' Using Left Joins: SELECT * FROM A LEFT JOIN B ON B.id=A.bid LEFT JOIN C ON C.id=B.cid WHERE A.id = '12345' Here is the actual query Here it is.. both return the same result Query (0.2693sec) : EXPLAIN EXTENDED SELECT * FROM friend_events, zcms_users, user_events, EVENTS WHERE friend_events.userid = '13006' AND friend_events.state =0 AND UNIX_TIMESTAMP( friend_events.t ) >=1258923485 AND friend_events.xid = user_events.id AND user_events

I have two tables : tableA (idA, titleA) and tableB (idB, idA, textB) with a one to many relationship between them. For each row in tableA, I want to retrieve the last 5 rows corresponding in tableB (ordered by idB). I've tried SELECT * FROM tableA INNER JOIN tableB ON tableA.idA = tableB.idA LIMIT 5 but it's just limiting the global result of INNER JOIN whereas I want to limit the result for each different tableA.id How can I do that ? Thanks Karol I think this is what you need: SELECT tableA.idA, tableA.titleA, temp.idB, temp.textB FROM tableA INNER JOIN ( SELECT tB1.idB, tB2.idA, ( SELECT

Which of the following query is better... This is just an example, there are numerous situations, where I want the user name to be displayed instead of UserID Select EmailDate, B.EmployeeName as [UserName], EmailSubject from Trn_Misc_Email as A inner join Mst_Users as B on A.CreatedUserID = B.EmployeeLoginName or Select EmailDate, GetUserName(CreatedUserID) as [UserName], EmailSubject from Trn_Misc_Email If there is no performance benefit in using the First, I would prefer using the second... I would be having around 2000 records in User Table and 100k records in email table... Thanks A good

I seem to be having some difficulty with a query in hibernate. I am performing an inner join on two tables. SELECT * FROM product p INNER JOIN warehouse w ON p.wid = w.id Product Table: id | name | wid | price | stock ..... Warehouse Table: id | name | city | lat | long ..... The join result: id | name | wid | price | stock | id | name | city | lat | long ..... When I run the query.. Session.createSQLQuery(this.query) .addEntity("p", Product.class) .addEntity("w", Warehouse.class).list(); So for every result I get an object containing a Product object and a Warehouse object . This is expected.

Graphical Explaination Table 1's columns: |a|b|c|d|e| Table 2's columns: |a|x|y|z| I want only a, b, c, d, e, x. I only want column a from table 1, not column a from table 2. Wordy Explaination I have two tables with one column sharing a common name. If I use a Select * and use an inner join, I get all the columns returned including two columns with the same name. I want to select everything from the first table, and only one column from the second table. Right now I am specifing every single column I need, which is a drag. Is there an easier way to grab everything from the first table and

Today I learned about a thing in SQL Server called INNER LOOP JOIN . What does this mean? (Google is not helping .. or should I say ... the blog posts about it are a bit .. technical and are blowing my mind). Also, what are some common scenarios that would be a good idea to use an INNER LOOP JOIN over a standard INNER JOIN ? Ash LOOP | HASH | MERGE are Join hints, specifying that the join in the query should use looping, hashing, or merging. Using LOOP |HASH | MERGE JOIN enforces a particular join between two tables. LOOP cannot be specified together with RIGHT or FULL as a join type. You