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• MSSQL in ASP.NET application getting unstable after a certain period

  - by Barslett

  Hello, I have an ASP.NET 2.0 application that I made to keep track of disruption reports about our public transport system. The architecture is pretty straight-forward; an MSSQL Express 2008 database, ADO.NET and a DataSet/DAL with a few methods to access the database. There is a set of .aspx pages for the UI in use by our dispatchers and on our public website, as well as a set of SOAP and REST webservices and an RSS feed. Everything worked just fine for more than a year, until two weeks ago. Now and then, it seems as the database enters an unstable mode, and the application starts responding something right, something wrong. The typical error is that apparently, an empty DataTable is returned to the public disruption overview or to the RSS generator. Thus, the user gets e.g. an empty GridView, but no exception is thrown AFAIK, and nothing is written to the Windows Application log. After a restart of the MSSQL Express service, the situation is back to normal. It has to be said that the situation first time appeared a few days after I made a new minor upgrade of the application. The RSS generator was slightly rewritten, and I added a WCF REST service. But the DAL and the database schema were untouched... Any hints of how we could keep the database stable? It is a bit annoying not to have a clue ;-)

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• Correlate GROUP BY and LEFT JOIN on multiple criteria to show latest record?

  - by Sunbird

  In a simple stock management database, quantity of new stock is added and shipped until quantity reaches zero. Each stock movement is assigned a reference, only the latest reference is used. In the example provided, the latest references are never shown, the stock ID's 1,4 should have references charlie, foxtrot respectively, but instead show alpha, delta. How can a GROUP BY and LEFT JOIN on multiple criteria be correlated to show the latest record? http://sqlfiddle.com/#!2/6bf37/107 CREATE TABLE stock ( id tinyint PRIMARY KEY, quantity int, parent_id tinyint ); CREATE TABLE stock_reference ( id tinyint PRIMARY KEY, stock_id tinyint, stock_reference_type_id tinyint, reference varchar(50) ); CREATE TABLE stock_reference_type ( id tinyint PRIMARY KEY, name varchar(50) ); INSERT INTO stock VALUES (1, 10, 1), (2, -5, 1), (3, -5, 1), (4, 20, 4), (5, -10, 4), (6, -5, 4); INSERT INTO stock_reference VALUES (1, 1, 1, 'Alpha'), (2, 2, 1, 'Beta'), (3, 3, 1, 'Charlie'), (4, 4, 1, 'Delta'), (5, 5, 1, 'Echo'), (6, 6, 1, 'Foxtrot'); INSERT INTO stock_reference_type VALUES (1, 'Customer Reference'); SELECT stock.id, SUM(stock.quantity) as quantity, customer.reference FROM stock LEFT JOIN stock_reference AS customer ON stock.id = customer.stock_id AND stock_reference_type_id = 1 GROUP BY stock.parent_id

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• Select the first row in a join of two tables in one statement

  - by Oscar Cabrero

  hi i need to select only the first row from a query that joins tables A and B, on table B exist multiple records with same name. there are not identifiers in any of the two tables. i cannt change the scheme either because i do not own the DB TABLE A NAME TABLE B NAME DATA1 DATA2 Select Distinct A.NAME,B.DATA1,B.DATA2 From A Inner Join B on A.NAME = B.NAME this gives me NAME DATA1 DATA2 sameName 1 2 sameName 1 3 otherName 5 7 otherName 8 9 but i need to retrieve only one row per name NAME DATA1 DATA2 sameName 1 2 otherName 5 7 i was able to do this by adding the result into a temp table with a identity column and the select the Min Id per name. the problem here is that i require to do this in one single statement. this is a DB2 database thanks

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• Does the optimizer filter subqueries with outer where clauses

  - by Mongus Pong

  Take the following query: select * from ( select a, b from c UNION select a, b from d ) where a = 'mung' Will the optimizer generally work out that I am filtering a on the value 'mung' and consequently filter mung on each of the queries in the subquery. OR will it run each query within the subquery union and return the results to the outer query for filtering (as the query would perhaps suggest) In which case the following query would perform better : select * from ( select a, b from c where a = 'mung' UNION select a, b from d where a = 'mung' ) Obviously query 1 is best for maintenance, but is it sacrificing much performace for this? Which is best?

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• Same query has nested loops when used with INSERT, but Hash Match without.

  - by AaronLS

  I have two tables, one has about 1500 records and the other has about 300000 child records. About a 1:200 ratio. I stage the parent table to a staging table, SomeParentTable_Staging, and then I stage all of it's child records, but I only want the ones that are related to the records I staged in the parent table. So I use the below query to perform this staging by joining with the parent tables staged data. --Stage child records INSERT INTO [dbo].[SomeChildTable_Staging] ([SomeChildTableId] ,[SomeParentTableId] ,SomeData1 ,SomeData2 ,SomeData3 ,SomeData4 ) SELECT [SomeChildTableId] ,D.[SomeParentTableId] ,SomeData1 ,SomeData2 ,SomeData3 ,SomeData4 FROM [dbo].[SomeChildTable] D INNER JOIN dbo.SomeParentTable_Staging I ON D.SomeParentTableID = I.SomeParentTableID; The execution plan indicates that the tables are being joined with a Nested Loop. When I run just the select portion of the query without the insert, the join is performed with Hash Match. So the select statement is the same, but in the context of an insert it uses the slower nested loop. I have added non-clustered index on the D.SomeParentTableID so that there is an index on both sides of the join. I.SomeParentTableID is a primary key with clustered index. Why does it use a nested loop for inserts that use a join? Is there a way to improve the performance of the join for the insert?

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• MySQL - are FK's useful / viable in a web app?

  - by yoda

  Hi all, I've encountered this discussion related to FK's and web applications. Basically some people say that FK's in web applications doesn't represent a real improvement and can even make the application slower in some cases. What do you guys think, what's your experience? -- A quote from Heikki Tuuri, creator of InnoDB engine, founder and CEO of Innobase: InnoDB checks foreign keys as soon as a row is updated, no batching is performed or checks delayed till transaction commit Foreign keys are often serious performance overhead, but help maintain data consistency Foreign Keys increase amount of row level locking done and can make it spread to a lot of tables besides the ones directly updated

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• C# Select clause returns system exception instead of relevant object

  - by Kashif

  I am trying to use the select clause to pick out an object which matches a specified name field from a database query as follows: objectQuery = from obj in objectList where obj.Equals(objectName) select obj; In the results view of my query, I get: base {System.SystemException} = {"Boolean Equals(System.Object)"} Where I should be expecting something like a Car, Make, or Model Would someone please explain what I am doing wrong here? The method in question can be seen here: // this function searches the database's table for a single object that matches the 'Name' property with 'objectName' public static T Read<T>(string objectName) where T : IEquatable<T> { using (ISession session = NHibernateHelper.OpenSession()) { IQueryable<T> objectList = session.Query<T>(); // pull (query) all the objects from the table in the database int count = objectList.Count(); // return the number of objects in the table // alternative: int count = makeList.Count<T>(); IQueryable<T> objectQuery = null; // create a reference for our queryable list of objects T foundObject = default(T); // create an object reference for our found object if (count > 0) { // give me all objects that have a name that matches 'objectName' and store them in 'objectQuery' objectQuery = from obj in objectList where obj.Equals(objectName) select obj; // make sure that 'objectQuery' has only one object in it try { foundObject = (T)objectQuery.Single(); } catch { return default(T); } // output some information to the console (output screen) Console.WriteLine("Read Make: " + foundObject.ToString()); } // pass the reference of the found object on to whoever asked for it return foundObject; } } Note that I am using the interface "IQuatable<T>" in my method descriptor. An example of the classes I am trying to pull from the database is: public class Make: IEquatable<Make> { public virtual int Id { get; set; } public virtual string Name { get; set; } public virtual IList<Model> Models { get; set; } public Make() { // this public no-argument constructor is required for NHibernate } public Make(string makeName) { this.Name = makeName; } public override string ToString() { return Name; } // Implementation of IEquatable<T> interface public virtual bool Equals(Make make) { if (this.Id == make.Id) { return true; } else { return false; } } // Implementation of IEquatable<T> interface public virtual bool Equals(String name) { if (this.Name.Equals(name)) { return true; } else { return false; } } } And the interface is described simply as: public interface IEquatable<T> { bool Equals(T obj); }

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• Computed column should result to string

  - by strakastroukas

  Here is a snap of my database. Both col1 and col2 are declared as int. My ComputedColumn currently adds the Columns 1 and 2, as follows... col1 col2 ComputedColumn 1 2 3 4 1 5 Instead of this, my ComputedColumn should join the columns 1 and 2 (includimg the '-' character in the middle) as follows... col1 col2 ComputedColumn 1 2 1-2 4 1 4-1 So, what is the correct syntax?

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• Primary key/foreign Key naming convention

  - by Jeremy

  In our dev group we have a raging debate regarding the naming convention for Primary and Foreign Keys. There's basically two schools of thought in our group: 1) Primary Table (Employee) Primary Key is called ID Foreign table (Event) Foreign key is called EmployeeID 2) Primary Table (Employee) Primary Key is called EmployeeID Foreign table (Event) Foreign key is called EmployeeID I prefer not to duplicate the name of the table in any of the columns (So I prefer option 1 above). Conceptually, it is consisted with a lot of the recommended practices in other languages, where you don't use the name of the object in its property names. I think that naming the foreign key EmployeeID (or Employee_ID might be better) tells the reader that it is the ID column of the Employee Table. Some others prefer option 2 where you name the primary key prefixed with the table name so that the column name is the same throughout the database. I see that point, but you now can not visually distinguish a primary key from a foreign key. Also, I think it's redundant to have the table name in the column name, because if you think of the table as an entity and a column as a property or attribute of that entity, you think of it as the ID attribute of the Employee, not the EmployeeID attribute of an employee. I don't go an ask my coworker what his PersonAge or PersonGender is. I ask him what his Age is. So like I said, it's a raging debate and we go on and on and on about it. I'm interested to get some new perspective.

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• mysql whats wrong with this query?

  - by Hailwood

  I'm trying to write a query that selects from four tables campaignSentParent csp campaignSentEmail cse campaignSentFax csf campaignSentSms css Each of the cse, csf, and css tables are linked to the csp table by csp.id = (cse/csf/css).parentId The csp table has a column called campaignId, What I want to do is end up with rows that look like: | id | dateSent | emailsSent | faxsSent | smssSent | | 1 | 2011-02-04 | 139 | 129 | 140 | But instead I end up with a row that looks like: | 1 | 2011-02-03 | 2510340 | 2510340 | 2510340 | Here is the query I am trying SELECT csp.id id, csp.dateSent dateSent, COUNT(cse.parentId) emailsSent, COUNT(csf.parentId) faxsSent, COUNT(css.parentId) smsSent FROM campaignSentParent csp, campaignSentEmail cse, campaignSentFax csf, campaignSentSms css WHERE csp.campaignId = 1 AND csf.parentId = csp.id AND cse.parentId = csp.id AND css.parentId = csp.id; Adding GROUP BY did not help, so I am posting the create statements. csp CREATE TABLE `campaignsentparent` ( `id` int(11) NOT NULL AUTO_INCREMENT, `campaignId` int(11) NOT NULL, `dateSent` datetime NOT NULL, `account` int(11) NOT NULL, `status` varchar(15) NOT NULL DEFAULT 'Creating', PRIMARY KEY (`id`) ) ENGINE=MyISAM AUTO_INCREMENT=2 DEFAULT CHARSET=latin1 cse/csf (same structure, different names) CREATE TABLE `campaignsentemail` ( `id` int(11) NOT NULL AUTO_INCREMENT, `parentId` int(11) NOT NULL, `contactId` int(11) NOT NULL, `content` text, `subject` text, `status` varchar(15) DEFAULT 'Pending', PRIMARY KEY (`id`) ) ENGINE=MyISAM AUTO_INCREMENT=140 DEFAULT CHARSET=latin1 css CREATE TABLE `campaignsentsms` ( `id` int(11) NOT NULL AUTO_INCREMENT, `parentId` int(11) NOT NULL, `contactId` int(11) NOT NULL, `content` text, `status` varchar(15) DEFAULT 'Pending', PRIMARY KEY (`id`) ) ENGINE=MyISAM AUTO_INCREMENT=141 DEFAULT CHARSET=latin1

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• Analysis Services with excel as front end - is it possible to get the nicer UI that powerpivot provi

  - by AJM

  I have been looking into PowerPivot and concluded that for "self service BI" and ahoc buidling of cubes it has its uses. In particular I like the enhanced UI that you get from using PowerPivot rather than just using a PivotTable hooked up to an analysis services datasource. However it seems that hooking up PowerPivot to an existing analysis services cube is not a solution for "organisational BI". It is not always desireable to suck millions of rows into excel at once and the interface between PowerPivot and analysis services is very poor in my book. Hence the question is can an existing analysis services solution get the enhanced ui features that power pivot brings, withoout using powerpivot as the design tool? If powerpivot is aimed ad self service/personal BI then it seems bizare that the UI for this is better than for bigger/more costly analysis services solutions.

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• ASP.Net Gridview paging, pageindex always == 0.

  - by David Archer

  Hi all, Having a slight problem with my ASP.Net 3.5 app. I'm trying to get the program to pick up what page number has been clicked. I'm using ASP.Net's built in AllowPaging="True" function. It's never the same without code, so here it is: ASP.Net: <asp:GridView ID="GridView1" runat="server" CellPadding="4" ForeColor="#333333" GridLines="Vertical" Width="960px" AllowSorting="True" EnableSortingAndPagingCallbacks="True" AllowPaging="True" PageSize="25" > <RowStyle BackColor="#F7F6F3" ForeColor="#333333" /> <FooterStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" /> <PagerStyle BackColor="#284775" ForeColor="White" HorizontalAlign="Center" /> <SelectedRowStyle BackColor="#E2DED6" Font-Bold="True" ForeColor="#333333" /> <HeaderStyle BackColor="#5D7B9D" Font-Bold="True" ForeColor="White" /> <EditRowStyle BackColor="#999999" /> <AlternatingRowStyle BackColor="White" ForeColor="#284775" /> </asp:GridView> C#: var fillTable = from ft in db.IncidentDatas where ft.pUserID == Convert.ToInt32(ClientList.SelectedValue.ToString()) select new { Reference = ft.pRef.ToString(), Date = ft.pIncidentDateTime.Value.Date.ToShortDateString(), Time = ft.pIncidentDateTime.Value.TimeOfDay, Premesis = ft.pPremises.ToString(), Latitude = ft.pLat.ToString(), Longitude = ft.pLong.ToString() }; if (fillTable.Count() > 0) { GridView1.DataSource = fillTable; GridView1.DataBind(); var IncidentDetails = fillTable.ToList(); for (int i = 0; i < IncidentDetails.Count(); i++) { int pageno = GridView1.PageIndex; int pagenostart = pageno * 25; if (i >= pagenostart && i < (pagenostart + 25)) { //Processing } } } Any idea why GridView1.PageIndex is always = 0? The thing is, the processing works correctly for the grid view.... it will always go to the correct paging page, but it's always 0 when I try to get the number. Help!

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• How Can I Generate Random Unqiue Numbers in C#

  - by peace

  public int GenPurchaseOrderNum() { Random random = new Random(); _uniqueNum = random.Next(13287, 21439); return UniqueNum; } I removed unique constraint from the PONumber column in the db because an employee should only generate P.O. # when the deal is set. Otherwise, P.O. # would have 0. P.O. Number used to have unique constraint, this forces employee to generate P.O. in all cases so the db doesn't throw unique constraint error. Since i removed the unique constraint, any quote doesn't have P.O. will carry 0 value. Otherwise, a unique value is generated for P.O. #. However, i don't have a unique constraint in db which makes it hard for me to know whether the application generated P.O. # is unique or not. What should i do? I hope my question is clear enough

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• Querying Two Tables At Once

  - by John

  Hello, I am trying to do what I believe is called a join query. First, in a MySQL table called "login," I want to look up what "loginid" is in the record where "username" equals $profile. (This will be just one record / row in the MySQL table). Then, I want to take that "loginid" and look up all rows / records in a different MySQL table called "submission," and pull data that have that "loginid." This could possibly be more than one record / row. How do I do this? The code below doesn't seem to work. Thanks in advance, John $profile = mysql_real_escape_string($_GET['profile']); $sqlStr = "SELECT l.username, l.loginid, s.loginid, s.submissionid, s.title, s.url, s.datesubmitted, s.displayurl FROM submission AS s, login AS l WHERE l.username = '$profile', s.loginid = l.loginid ORDER BY s.datesubmitted DESC";

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• Database layout tagging system

  - by Kurresmack

  I am creating a web site for a customer and they want to be able to create articles. My idea is to tag them so I am going to implement the system. What is the best design, both from an architectural and a perfomance perspective: 1. To have table with all tags and then have a one to many relationship table that links a tag like this: articles table with ID tags table with ID one to many table with columns Article.ID and Tags.ID 2. To have one table with articles and one with tags for articles like this: articles table with ID tags table with Article.ID and tag text Thanks in advance!

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• Complex LINQ paging algorithm

  - by sharepointmonkey

  We have a list of projects that may or may not have a collection of subprojects. Our report needs to contain all the projects except those that are the parent project of a subproject. I need to page this into pages of, say, 25 rows. But if subprojects appear on that page then ALL the subprojects of that project must appear on the same page. So more than 25 items may appear if necessary. I've got as far as var pagedProjects = db.Projects.Where(x => !x.SubProjects.Any()).Skip( (pageNo -1) * pageSize).Take(pageSize); Obviously, this fails the second part of the requirements. As a further pain in the arse, I need to have a pager control on the report. So I'll need to be able to calculate the total number of pages. I could loop through the whole table of projects but the performance will suffer. Can anybody come up with a paged solution? EDIT - I should probably mention that SubProjects joins back onto Projects via a selfreferencing foreign key so the whole lot comes back as an IQueryable<Project>.

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• Oracle - Updating one column or another based on a condition

  - by z-dan

  I want to update a record in a table but based on a condition I will either update one column or another but I do not want to have 2 separate statements because the statements are very long and detailed. Here is the basic idea with over simplification to get to the point. PROCEDURE Animal_something(p_updater VARCHAR2) begin if p_updater = 'person' then -- I want to update the modified_by else -- if p_updater = 'a process' I want to update modified_by_process Update table_creatures set animal_type = 'Dog , **modified_by** = 'Bob' **or do this** **modified_by_process =** 'creature_package' where animal_legs = '4' I don't want: if p_updater = 'person' then Update table_creatures set animal_type = 'Dog , modified_by = 'Bob' where animal_legs = '4'; else Update table_creatures set animal_type = 'Dog , modified_by_process = 'creature_package' where animal_legs = '4'; end;

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• WPF/.NET data access models - resource recommendations

  - by jasonk

  We're in the early design/prep phases of transferring/updating a rather large "legacy" 3 tier client-server app to a new version. We’re looking at doing WPF over Winforms as it appears to be the direction Microsoft is pushing development of the future and we’d like the maximize the life cycle/span of the apps. That said during the rewrite we’d like to make as many changes to our data access/presentation model to improve performance as much as possible up front as many. I’ve been doing some research along that vein but the vast majority of the resources I've found that discuss WPF focus only simple data tracking apps or focus on the very basics UI design/controls. The few items that even discuss data presentation are fairly elementary in depth. Are there any books/articles/recommended reading/other resources recommended for development related to large enterprise level business apps? Any “gotchas” that should/could be avoided? General advice to minimize the time underwater

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• IN MSSQL 2008 is there a way to generate a report as to how much space on disk each table takes?

  - by Matt

  IN MSSQL 2008 is there a way to generate a report as to how much space on disk each table takes? I can do it one by one by checking the storage properties, but I was wondering if there was a way, maybe even a query to generate such a report.

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• Copying a subset of data to an empty database with the same schema

  - by user193655

  I would like to export part of a database full of data to an empty database. Both databases has the same schema. I want to maintain referential integrity. To simplify my cases it is like this: MainTable has the following fields: 1) MainID integer PK 2) Description varchar(50) 3) ForeignKey integer FK to MainID of SecondaryTable SecondaryTable has the following fields: 4) MainID integer PK (referenced by (3)) 5) AnotherDescription varchar(50) The goal I'm trying to accomplish is "export all records from MainTable using a WHERE condition", for example all records where MainID < 100. To do it manually I shuold first export all data from SecondaryTable contained in this select: select * from SecondaryTable ST outer join PrimaryTable PT on ST.MainID=PT.MainID then export the needed records from MainTable: select * from MainTable where MainID < 100. This is manual, ok. Of course my case is much much much omre complex, I have 200+ tables, so donig it manually is painful/impossible, I have many cascading FKs. Is there a way to force the copy of main table only "enforcing referntial integrity". so that my query is something like: select * from MainTable where MainID < 100 WITH "COPYING ALL FK sources" In this cases also the field (5) will be copied. ====================================================== Is there a syntax or a tool to do this? Table per table I'd like to insert conditions (like MainID <100 is only for MainTable, but I have also other tables).

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• NHibernate complex order query

  - by manu08

  Here's my simplified domain public class Notification { public Guid ID { get; set; } public string Name { get; set; } public IEnumerable<Location> Locations { get; set; } } public class Location { public Guid Id { get; set; } public string Name { get; set; } public decimal Longitude { get; set; } public decimal Latitude { get; set; } } Notifications and Locations have a many-to-many relationship (defined in table LocationsOnNotification). What I'd like to do is query for the nearest 10 Notifications from a given longitude and latitude. I've been trying to use ICriteria, but I'm not sure how to specify the ordering correctly: return Session.CreateCriteria<Notification>() .SetFirstResult(firstIndex) .SetMaxResults(maxResults) .AddOrder(Order.Asc( WHAT GOES HERE! )) .List<Notification>(); What I've been thinking of so far is adding a formula property to the Location mapping; something like this: <property name='Distance' formula='lots of geometry'/> But I'm not sure if that can take in parameters (since I'd need to pass in the user's location to calculate the distance), plus I'm not sure how to specify it in the Order.Asc clause given that it's a property on a many-to-many association class. Any ideas? Or perhaps I should take a different approach altogether. Thanks in advance!

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• Need help with a conditional SELECT statement

  - by Ethan

  I've got a stored procedure with a select statement, like this: `SELECT author_ID, author_name, author_bio FROM Authors WHERE author_ID in (SELECT author_ID from Books) ` This limits results to authors who have book records. This is the Books table: Books book_ID INT author_ID INT book_title NVARCHAR featured_book BIT What I want to do is conditionally select the ID of the featured book by each author as part of the select statement above, and if none of the books for a given author are featured, select the ID of the first (top 1) book by the author from the books table. How do I approach this?

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• I would like to make a field part of a many to many relationship

  - by jona

  I have the following table called stores id store zip 1 Market 1 01569 2 Market 2 01551 3 Market 3 10468 4 Market 4 10435 Zip code table INSERT INTO `zip_codes` (`restaurants_locations_id`, `zip`, `state`, `latitude`, `longitude`, `city`, `full_state`) VALUES (1, '06001', 'CT', ' 41.789698', ' -72.86431', 'Avon', 'Connecticut'), (2, '06002', 'CT', ' 41.832798', ' -72.72642', 'Bloomfield', 'Connecticut'), (3, '06010', 'CT', ' 41.682249', ' -72.93365', 'Bristol', 'Connecticut'), (4, '06013', 'CT', ' 41.758415', ' -72.94642', 'Burlington', 'Connecticut'), (5, '06016', 'CT', ' 41.909097', ' -72.54393', 'Windsorville', 'Connecticut'), (6, '06018', 'CT', ' 42.023510', ' -73.31103', 'Canaan', 'Connecticut'), (7, '06019', 'CT', ' 41.834247', ' -72.89174', 'Canton', 'Connecticut'), etc.... what I want is to create a table which will connect the zip field in the stores tables where one store will be found in several zicodes... How would that table would look like? Thanks

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• How do I find the top N batters per year?

  - by Drew Stephens

  I'm playing around with the Lahman Baseball Database in a MySQL instance. I want to find the players who topped home runs (HR) for each year. The Batting table has the following (relevant parts) of its schema: +-----------+----------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+----------------------+------+-----+---------+-------+ | playerID | varchar(9) | NO | PRI | | | | yearID | smallint(4) unsigned | NO | PRI | 0 | | | HR | smallint(3) unsigned | YES | | NULL | | +-----------+----------------------+------+-----+---------+-------+ For each year, every player has an entry (between hundreds and 12k per year, going back to 1871). Getting the top N hitters for a single year is easy: SELECT playerID,yearID,HR FROM Batting WHERE yearID=2009 ORDER BY HR DESC LIMIT 3; +-----------+--------+------+ | playerID | yearID | HR | +-----------+--------+------+ | pujolal01 | 2009 | 47 | | fieldpr01 | 2009 | 46 | | howarry01 | 2009 | 45 | +-----------+--------+------+ But I'm interested in finding the top 3 from every year. I've found solutions like this, describing how to select the top from a category and I've tried to apply it to my problem, only to end up with a query that never returns: SELECT b.yearID, b.playerID, b.HR FROM Batting AS b LEFT JOIN Batting b2 ON (b.yearID=b2.yearID AND b.HR <= b2.HR) GROUP BY b.yearID HAVING COUNT(*) <= 3; Where have I gone wrong?

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• Using CASE Statements in LEFT OUTER JOIN in SQL

  - by s khan

  I've got a scenario where I want to switch on two different tables in an outer join. It goes something like this:- select mytable.id, yourtable.id from mytable left outer join (case when mytable.id = 2 then table2 yourtable on table1.id = table2.id else table3 yourtable on table1.id = table3.id end) ...but it doesn't work. Any suggestions?

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