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• Generate dynamic UPDATE command from Expression<Func<T, T>>

  - by Rui Jarimba

  I'm trying to generate an UPDATE command based on Expression trees (for a batch update). Assuming the following UPDATE command: UPDATE Product SET ProductTypeId = 123, ProcessAttempts = ProcessAttempts + 1 For an expression like this: Expression<Func<Product, Product>> updateExpression = entity => new Product() { ProductTypeId = 123, ProcessAttempts = entity.ProcessAttempts + 1 }; How can I generate the SET part of the command? SET ProductTypeId = 123, ProcessAttempts = ProcessAttempts + 1

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• How to return a record from function executed by INSERT/UPDATE rule?

  - by seas

  Do the following scheme for my database: create sequence data_sequence; create table data_table { id integer primary key; field varchar(100); }; create view data_view as select id, field from data_table; create function data_insert(_new data_view) returns data_view as $$declare _id integer; _result data_view%rowtype; begin _id := nextval('data_sequence'); insert into data_table(id, field) values(_id, _new.field); select * into _result from data_view where id = _id; return _result; end; $$ language plpgsql; create rule insert as on insert to data_view do instead select data_insert(new); Then type in psql: insert into data_view(field) values('abc'); Would like to see something like: id | field ----+--------- 1 | abc Instead see: data_insert ------------- (1, "abc") Is it possible to fix this somehow? Thanks for any ideas. Ultimate idea is to use this in other functions, so that I could obtain id of just inserted record without selecting for it from scratch. Something like: insert into data_view(field) values('abc') returning id into my_variable would be nice but doesn't work with error: ERROR: cannot perform INSERT RETURNING on relation "data_view" HINT: You need an unconditional ON INSERT DO INSTEAD rule with a RETURNING clause. I don't really understand that HINT. I use PostgreSQL 8.4.

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• MySQL break out group clause from subquery

  - by Anton Gildebrand

  Here is my query SELECT COALESCE(js.name,'Lead saknas'), count(j.id) FROM jobs j LEFT JOIN job_sources js ON j.job_source=js.id LEFT JOIN (SELECT * FROM quotes GROUP BY job_id) q ON j.id=q.job_id GROUP BY j.job_source The problem is that it's allowed for each job to have more than one quote. Because of that i group the quotes by job_id. Now sure, this works. But i don't like the solution with a subquery. How can i break out the group clause from the subquery to the main query? I have tried to add q.job_id to the main group clause, both before and after the existing one but don't get the same results.

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• Why isn't the Cache invalidated after table update using the SqlCacheDependency?

  - by Jason

  I have been trying to get SqlCacheDependency working. I think I have everything set up correctly, but when I update the table, the item in the Cache isn't invalidated. Can you look at my code and see if I am missing anything? I enabled the Service Broker for the Sandbox database. I have placed the following code in the Global.asax file. I also restart IIS to make sure it is called. void Application_Start(object sender, EventArgs e) { SqlDependency.Start(ConfigurationManager.ConnectionStrings["SandboxConnectionString"].ConnectionString); } I have placed this entry in the web.config file: <system.web> <caching> <sqlCacheDependency enabled="true" pollTime="10000"> <databases> <add name="Sandbox" connectionStringName="SandboxConnectionString"/> </databases> </sqlCacheDependency> </caching> </system.web> I call this code to put the item into the cache: protected void CacheDataSetButton_Click(object sender, EventArgs e) { using (SqlConnection sqlConnection = new SqlConnection(ConfigurationManager.ConnectionStrings["SandboxConnectionString"].ConnectionString)) { using (SqlCommand sqlCommand = new SqlCommand("SELECT PetID, Name, Breed, Age, Sex, Fixed, Microchipped FROM dbo.Pets", sqlConnection)) { using (SqlDataAdapter sqlDataAdapter = new SqlDataAdapter(sqlCommand)) { DataSet petsDataSet = new DataSet(); sqlDataAdapter.Fill(petsDataSet, "Pets"); SqlCacheDependency petsSqlCacheDependency = new SqlCacheDependency(sqlCommand); Cache.Insert("Pets", petsDataSet, petsSqlCacheDependency, DateTime.Now.AddSeconds(10), Cache.NoSlidingExpiration); } } } } Then I bind the GridView with this code: protected void BindGridViewButton_Click(object sender, EventArgs e) { if (Cache["Pets"] != null) { GridView1.DataSource = Cache["Pets"] as DataSet; GridView1.DataBind(); } } Between attempts to DataBind the GridView, I change the table's values expecting it to invalidate the Cache["Pets"] item, but it seems to stay in the Cache indefinitely.

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• Conditionally Summing the same Column multiple times in a single select statement?

  - by btollett

  I have a single table that shows employee deployments, for various types of deployment, in a given location for each month: ID | Location_ID | Date | NumEmployees | DeploymentType_ID As an example, a few records might be: 1 | L1 | 12/2010 | 7 | 1 (=Permanent) 2 | L1 | 12/2010 | 2 | 2 (=Temp) 3 | L1 | 12/2010 | 1 | 3 (=Support) 4 | L1 | 01/2011 | 4 | 1 5 | L1 | 01/2011 | 2 | 2 6 | L1 | 01/2011 | 1 | 3 7 | L2 | 12/2010 | 6 | 1 8 | L2 | 01/2011 | 6 | 1 9 | L2 | 12/2010 | 3 | 2 What I need to do is sum the various types of people by date, such that the results look something like this: Date | Total Perm | Total Temp | Total Supp 12/2010 | 13 | 5 | 1 01/2011 | 10 | 2 | 1 Currently, I've created a separate query for each deployment type that looks like this: SELECT Date, SUM(NumEmployees) AS "Total Permanent" FROM tblDeployment WHERE DeploymentType_ID=1 GROUP BY Date; We'll call that query qSumPermDeployments. Then, I'm using a couple of joins to combine the queries: SELECT qSumPermDeployments.Date, qSumPermDeployments.["Total Permanent"] AS "Permanent" qSumTempDeployments.["Total Temp"] AS "Temp" qSumSupportDeployments.["Total Support"] AS Support FROM (qSumPermDeployments LEFT JOIN qSumTempDeployments ON qSumPermDeployments.Date = qSumTempDeployments.Date) LEFT JOIN qSumSupportDeployments ON qSumPermDeployments.Date = qSumSupportDeployments.Date; Note that I'm currently constructing that final query under the assumption that a location will only have temp or support employees if they also have permanent employees. Thus, I can create the joins using the permanent employee results as the base table. Given all of the data I currently have, that assumption holds up, but ideally I'd like to move away from that assumption. So finally, my question. Is there a way to simplify this down to a single query or is it best to separate it out into multiple queries - if for no other reason that readability.

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• Select proper columns from JOIN statement

  - by Alexander Stalt

  I have two tables: table1, table2. Table1 has 10 columns, table2 has 2 columns. SELECT * FROM table1 AS T1 INNER JOIN table2 AS T2 ON T1.ID = T2.ID I want to select all columns from table1 and only 1 column from table2. Is it possible to do that without enumerating all columns from table1 ?

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• need help in c# for loops

  - by hala

  sory for that arabic part but i dont now englich much ?? ???? ?? ???? ???????? foreach(int i in array1) { Console.Writeln(i); } what is console ?? ???

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• Assign values from same table

  - by Reddy S R

  I have a database table with parent child relationships between different rows. 1 parent can have any number of children. Children do not have children. I want to copy 'Message' from 'Parent Category' to child categories. CategoryID Name Value Message ParentID DeptId 1 Books 9 Specials 1 2 Music 7 1 3 Paperback 25 1 1 4 PDFs 26 1 2 5 CDs 35 2 1 If that was sample data, Paperback should have Specials as it's Message after the query is run. I have gotten the child rows (the query runs very slow, don't know why), but how do I get the data and assign it to appropriate child rows? --@DeptId = 1 select * from Categories where ParentID in( select CategoryID from Categories where DeptID = @DeptId ) I would like to see a solution that would not use cursors. Thanks

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• Scalable Database Tagging Schema

  - by Longpoke

  EDIT: To people building tagging systems. Don't read this. It is not what you are looking for. I asked this when I wasn't aware that RDBMS all have their own optimization methods, just use a simple many to many scheme. I have a posting system that has millions of posts. Each post can have an infinite number of tags associated with it. Users can create tags which have notes, date created, owner, etc. A tag is almost like a post itself, because people can post notes about the tag. Each tag association has an owner and date, so we can see who added the tag and when. My question is how can I implement this? It has to be fast searching posts by tag, or tags by post. Also, users can add tags to posts by typing the name into a field, kind of like the google search bar, it has to fill in the rest of the tag name for you. I have 3 solutions at the moment, but not sure which is the best, or if there is a better way. Note that I'm not showing the layout of notes since it will be trivial once I get a proper solution for tags. Method 1. Linked list tagId in post points to a linked list in tag_assoc, the application must traverse the list until flink=0 post: id, content, ownerId, date, tagId, notesId tag_assoc: id, tagId, ownerId, flink tag: id, name, notesId Method 2. Denormalization tags is simply a VARCHAR or TEXT field containing a tab delimited array of tagId:ownerId. It cannot be a fixed size. post: id, content, ownerId, date, tags, notesId tag: id, name, notesId Method 3. Toxi (from: http://www.pui.ch/phred/archives/2005/04/tags-database-schemas.html, also same thing here: http://stackoverflow.com/questions/20856/how-do-you-recommend-implementing-tags-or-tagging) post: id, content, ownerId, date, notesId tag_assoc: ownerId, tagId, postId tag: id, name, notesId Method 3 raises the question, how fast will it be to iterate through every single row in tag_assoc? Methods 1 and 2 should be fast for returning tags by post, but for posts by tag, another lookup table must be made. The last thing I have to worry about is optimizing searching tags by name, I have not worked that out yet. I made an ASCII diagram here: http://pastebin.com/f1c4e0e53

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• Select where and where not

  - by Simon

  I have a table containing lessons that I called "cours" (french) and I have several cours inside and I have linked them to students with a table between them to see if they go to the lessons or not. I would like to return data with the SELECT and the data that are NOT select. So, If one student follow 3 courses of 5, I would like to return the 3 courses that he follow and the 2 courses that he doesn't follow. Is there a way to do it ?

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• Little Employee/Shift timetable HELP!!!

  - by DAVID

  Morning Guys, I have the following tables: operator(ope_id, ope_name) ope_shift(ope_id, shift_id, shift_date) shift(shift_id, shift_start, shift_end) here is a better view of the data http://latinunit.net/emp_shift.txt here is the screenshot of a select statement to the tables http://img256.imageshack.us/img256/4013/opeshift.jpg im using this code SELECT OPE_ID, COUNT(OPE_ID) AS Total_shifts from operator_shift group by ope_id; to view the current total shifts per operator and it works, BUT if there was 500 more rows it would count them all aswell, THE QUESTION is, anyone has a better way of making my database work, or how can i tell the system that those rows are a whole month, i remember i friend said something about count then devide by 30 but im not sure, what if the month isnt finished? and you want to show the emp with highest shifts to date

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• Accessing non-related entities in LinqToSql entity classes

  - by Chris Johnson

  In LinqToSql, if I want to access a non-related entity in an entity partial class, how do I do this without creating a new DataContext? Here's the scenario: I have the tables Client, IssueType and ClientIssueType. A Client may specify a list of IssueTypes if they do not want to use the default IssueTypes. I have the default IssueTypes in the ClientIssueType table with a ClientId of null. In my Client partial I'd like to try to retrieve all IssueTypes, and if none are found, return all default IssueTypes. The only way I can see of accessing the IssueTypes with a null ClientId is by accessing the table through a new DataContext, which is problematic once I want to start assigning them to Issues. Where am I going wrong?

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• MySQL Database Design with Internationalization

  - by Some name

  Hello, I'm going to start work on a medium sized application, and i'm planning it's db design. One thing that I'm not sure about is this. I will have many tables which will need internationalization, such as: "membership_options, gender_options, language_options etc" Each of these tables will share common i18n fields, like: "title, alternative_title, short_description, description" In your opinion which is the best way to do it? Have an i18n table with the same fields for each of the tables that will need them? or do something like: Membership table Gender table ---------------- -------------- id | created_at id | created_at 1 - 22.03.2001 1 - 14.08.2002 2 - 22.03.2001 2 - 14.08.2002 General translation table ------------------------- record_id | table_name | string_name | alternative_title| .... |id_language 1 - membership regular null 1 (english) 1 - membership normale null 2 (italian) 1 - gender man null 1(english) 1 -gender uomo null 2(italian) This would avoid me repeating something like: membership_translation table ----------------------------- membership_id | name | alternative_title | id_lang 1 regular null 1 1 normale null 2 gender_translation table ----------------------------- gender_id | name | alternative_title | id_lang 1 man null 1 1 uomo null 2 and so on, so i would probably reduce the number of db tables, but i'm not sure about performance.I'm not much of a DB designer, so please let me know.

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• MySQL Query: Winning Auction Bid

  - by mabwi

  I have a small Bidding system that I'm using for a fantasy auction draft. I'm trying to use the below query to pull up the max bids on each player. However, it's not actually giving me the max bid, it's just giving me the first one entered in to the database. SELECT Bid.id FROM bids AS Bid WHERE Bid.active =1 GROUP BY player_id HAVING MAX( Bid.amount ) Here's the Bid table layout, in case it helps: CREATE TABLE IF NOT EXISTS `bids` ( `id` int(10) NOT NULL AUTO_INCREMENT, `user_id` int(10) NOT NULL, `player_id` int(10) NOT NULL, `amount` int(6) NOT NULL, `timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, `winning_bid` int(1) NOT NULL DEFAULT '0', `active` int(1) NOT NULL DEFAULT '1', PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 ;

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• Why does Linq to Entities generate Left Outer Joins?

  - by DJCasey

  I was wondering if anyone knew why linq to entities always seems to generate left outer joins. I would understand it on an optional relationship but it doesn't make good sense when the relationship is mandatory. Does anyone have any idea how to make it generate inner joins instead?

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• GridView will not update underlying data source

  - by John Christensen

  So I'm been pounding on this problem all day. I've got a LinqDataSource that points to my model and a GridView that consumes it. When I attempt to do an update on the GridView, it does not update the underlying data source. I thought it might have to do with the LinqDataSource, so I added a SqlDataSource and the same thing happens. The aspx is as follows (the code-behind page is empty): <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="Data Source=devsql32;Initial Catalog=Steam;Persist Security Info=True;" ProviderName="System.Data.SqlClient" SelectCommand="SELECT [LangID], [Code], [Name] FROM [Languages]" UpdateCommand="UPDATE [Languages] SET [Code]=@Code WHERE [LangID]=@LangId"> </asp:SqlDataSource> <asp:GridView ID="_languageGridView" runat="server" AllowPaging="True" AllowSorting="True" AutoGenerateColumns="False" DataKeyNames="LangId" DataSourceID="SqlDataSource1"> <Columns> <asp:CommandField ShowDeleteButton="True" ShowEditButton="True" /> <asp:BoundField DataField="LangId" HeaderText="Id" ReadOnly="True" /> <asp:BoundField DataField="Code" HeaderText="Code" /> <asp:BoundField DataField="Name" HeaderText="Name" /> </Columns> </asp:GridView> <asp:LinqDataSource ID="_languageDataSource" ContextTypeName="GeneseeSurvey.SteamDatabaseDataContext" runat="server" TableName="Languages" EnableInsert="True" EnableUpdate="true" EnableDelete="true"> </asp:LinqDataSource> What in the world am I missing here? This problem is driving me insane.

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• What's faster? select [object] or select new {[object].value1, [object].value2} with linq

  - by Darcy

  I was hoping some of you guru's out there know the answer to this question. Which is faster? A or B A: var item = from d in database select d; B: var item = from d in database select new {d.item1, d.item2}; SEEMINGLY, it seems like selecting part of the table object would be faster than selecting the entire object, but something tells me its not necessarily the case.

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• How to map combinations of things to a relational database?

  - by Space_C0wb0y

  I have a table whose records represent certain objects. For the sake of simplicity I am going to assume that the table only has one row, and that is the unique ObjectId. Now I need a way to store combinations of objects from that table. The combinations have to be unique, but can be of arbitrary length. For example, if I have the ObjectIds 1,2,3,4 I want to store the following combinations: {1,2}, {1,3,4}, {2,4}, {1,2,3,4} The ordering is not necessary. My current implementation is to have a table Combinations that maps ObjectIds to CombinationIds. So every combination receives a unique Id: ObjectId | CombinationId ------------------------ 1 | 1 2 | 1 1 | 2 3 | 2 4 | 2 This is the mapping for the first two combinations of the example above. The problem is, that the query for finding the CombinationId of a specific Combination seems to be very complex. The two main usage scenarios for this table will be to iterate over all combinations, and the retrieve a specific combination. The table will be created once and never be updated. I am using SQLite through JDBC. Is there any simpler way or a best practice to implement such a mapping?

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• Creating a foreign key in MySQL produces error:

  - by SnOrfus

  I'm trying to create a foreign key on a table in MySQL and I'm getting a strange error that there seems to be little info about in any of my searches. I'm creating the key with this (emitted from mysql workbench 5.2): ALTER TABLE `db`.`appointment` ADD CONSTRAINT `FK_appointment_CancellationID` FOREIGN KEY (`CancellationID` ) REFERENCES `db`.`appointment_cancellation` (`ID` ) ON DELETE NO ACTION ON UPDATE NO ACTION , ADD INDEX `FK_appointment_CancellationID` (`CancellationID` ASC) ; at which point I get the error: ERROR 1452: Cannot add or update a child row: a foreign key constraint fails (alarmtekcore., CONSTRAINT FK_lead_appointment_CancellationID FOREIGN KEY (CancellationID) REFERENCES lead_appointment_cancellation (`) I've checked here but there's no data in the table.

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• Writing a query to find MAX number in PL/SQL

  - by user2461116

  I am suppose to Write a query that will display the largest number of movies rented by one member and that member's name. Give the output column a meaningful name such as MAXIMUM NUMBER. This is what I have. select max(maximum_movies) from (select count(*)maximum_movies from mm_member join mm_rental on mm_rental.member_id = mm_member.member_id group by first, last); I got the maximum number but the output should be like this. First Last Maximum_movies John Doe 4 But the output is Maximum_movies 4 Any suggestions?

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• Best performance approach to history mechanism?

  - by Royi Namir

  We are going to create History Mechanism for our changes in DB (DART in pic) via Triggers. we have 600 tables. Each record that will be changed - the trigger will insert the deleted one into XXX. regarding to the XXX : option 1 : clone each table in "Dart" DB and each table now will have a "sister table" e.g. : Table1 will have Table1_History problems : we will have 1200 tables programmer can do mistakes by working on wrong tables... option 2 : make a new DB (DART_2005 in pic) and the history tables will be there option 3 : use linked server which stores the Db which will contain the history tables. question : 1) which option gives the best performance ( I guess 3 is not - but is it 1 or 2 or same ?) 2) Does option 2 is acting like "linked server" ( in queries we will need to select from both DB's...) 3) What is the best practice approach ?

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• MYSQL DELETE from a table [closed]

  - by Hossein

  Possible Duplicate: MySQL DELETE in a single table Hi, I have this table: userurltag(id,user,Url,tag) I want to remove rows that contain urls that are used by only one user, can someone help me? It seems that DELETE...(SELECT...) is not supported in Mysql.

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• Array not showing in Jlist but filled in console

  - by OVERTONE

  Hey there. been a busy debugger today. ill give ths short version. ive made an array list that takes names from a database. then i put the contents of the arraylist into an array of strings. now i want too display the arrays contents in a JList. the weird thing is it was working earlier. and ive two methods. ones just a little practice too make sure i was adding to the Jlist correctly. so heres the key codes. this is the layout of my code. variables constructor methods in my variables i have these 3 defined String[] contactListNames = new String[5]; ArrayList<String> rowNames = new ArrayList<String>(); JList contactList = new JList(contactListNames); simple enough. in my constructor i have them again. contactListNames = new String[5]; contactList = new JList(contactListNames); //i dont have the array list defined though. printSqlDetails(); // the prinSqldetails was too make sure that the connectionw as alright. and its working fine. fillContactList(); // this is the one thats causing me grief. its where all the work happens. // fillContactListTest(); // this was the tester that makes sure its adding to the list alright. heres the code for fillContactListTest() public void fillContactListTest() { for(int i = 0;i<3;i++) { try { String contact; System.out.println(" please fill the list at index "+ i); Scanner in = new Scanner(System.in); contact = in.next(); contactListNames[i] = contact; in.nextLine(); } catch(Exception e) { e.printStackTrace(); } } } heres the main one thats supposed too work. public void fillContactList() { int i =0; createConnection(); ArrayList<String> rowNames = new ArrayList<String>(); try { Statement stmt = conn.createStatement(); ResultSet namesList = stmt.executeQuery("SELECT name FROM Users"); try { while (namesList.next()) { rowNames.add(namesList.getString(1)); contactListNames =(String[])rowNames.toArray(new String[rowNames.size()]); // this used to print out contents of array list // System.out.println("" + rowNames); while(i<contactListNames.length) { System.out.println(" " + contactListNames[i]); i++; } } } catch(SQLException q) { q.printStackTrace(); } conn.commit(); stmt.close(); conn.close(); } catch(SQLException e) { e.printStackTrace(); } } i really need help here. im at my wits end. i just cant see why the first method would add to the JList no problem. but the second one wont. both the contactListNames array and array list can print fine and have the names in them. but i must be transfering them too the jlist wrong. please help p.s im aware this is long. but trust me its the short version.

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• Using sqlalchemy to query using multiple column where in clause

  - by crunkchitis

  I'm looking to execute this query using sqlalchemy. SELECT name, age, favorite_color, favorite_food FROM kindergarten_classroom WHERE (favorite_color, favorite_food) IN (('lavender','lentil soup'),('black','carrot juice')); I only want kids that like (lavender AND lentil soup) OR (black and carrot juice). This is similar, but doesn't get me all of the way there: Sqlalchemy in clause

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• How can I perform this query between related tables without using UNION?

  - by jeremy

  Suppose I have two separate tables that I watch to query. Both of these tables has a relation with a third table. How can I query both tables with a single, non UNION based query? I want the result of the search to rank the results by comparing a field on each table. Here's a theoretical example. I have a User table. That User can have both CDs and books. I want to find all of that user's books and CDs with a single query matching a string ("awesome" in this example). A UNION based query might look like this: SELECT "book" AS model, name, ranking FROM book WHERE name LIKE 'Awesome%' UNION SELECT "cd" AS model, name, ranking FROM cd WHERE name LIKE 'Awesome%' ORDER BY ranking DESC How can I perform a query like this without the UNION? If I do a simple left join from User to Books and CDs, we end up with a total number of results equal to the number of matching cds timse the number of matching books. Is there a GROUP BY or some other way of writing the query to fix this?

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