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• Why would using a Temp table be faster than a nested query?

  - by Mongus Pong

  We are trying to optimise some of our queries. One query is doing the following: SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, INTO [#Gadget] FROM task t SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) as Client FROM [#Gadget] order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC DROP TABLE [#Gadget] (I have removed the complex subquery, cos I dont think its relevant other than to explain why this query has been done as a two stage process.) Now I would have thought it would be far more efficient to merge this down into a single query using subqueries as : SELECT TOP 500 TaskID, Task, Tracker, ClientID, dbo.GetClientDisplayName(ClientID) FROM ( SELECT t.TaskID, t.Name as Task, '' as Tracker, t.ClientID, (<complex subquery>) Date, FROM task t ) as sub order by CASE WHEN Date IS NULL THEN 1 ELSE 0 END , Date ASC This would give the optimiser better information to work out what was going on and avoid any temporary tables. It should be faster. But it turns out it is a lot slower. 8 seconds vs under 5 seconds. I cant work out why this would be the case as all my knowledge of databases imply that subqueries would always be faster than using temporary tables. Can anyone explain what could be going on!?!?

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• Postgresql has broken apt-get on Ubuntu

  - by Raphie Palefsky-Smith

  On ubuntu 12.04, whenever I try to install a package using apt-get I'm greeted by: The following packages have unmet dependencies: postgresql-9.1 : Depends: postgresql-client-9.1 but it is not going to be instal led E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a so lution). apt-get install postgresql-client-9.1 generates: The following packages have unmet dependencies: postgresql-client-9.1 : Breaks: postgresql-9.1 (< 9.1.6-0ubuntu12.04.1) but 9.1.3-2 is to be installed apt-get -f install and apt-get remove postgresql-9.1 both give: Removing postgresql-9.1 ... * Stopping PostgreSQL 9.1 database server * Error: /var/lib/postgresql/9.1/main is not accessible or does not exist ...fail! invoke-rc.d: initscript postgresql, action "stop" failed. dpkg: error processing postgresql-9.1 (--remove): subprocess installed pre-removal script returned error exit status 1 Errors were encountered while processing: postgresql-9.1 E: Sub-process /usr/bin/dpkg returned an error code (1) So, apt-get is crippled, and I can't find a way out. Is there any way to resolve this without a re-install? EDIT: apt-cache show postgresql-9.1 returns: Package: postgresql-9.1 Priority: optional Section: database Installed-Size: 11164 Maintainer: Ubuntu Developers <[email protected]> Original-Maintainer: Martin Pitt <[email protected]> Architecture: amd64 Version: 9.1.6-0ubuntu12.04.1 Replaces: postgresql-contrib-9.1 (<< 9.1~beta1-3~), postgresql-plpython-9.1 (<< 9.1.6-0ubuntu12.04.1) Depends: libc6 (>= 2.15), libcomerr2 (>= 1.01), libgssapi-krb5-2 (>= 1.8+dfsg), libkrb5-3 (>= 1.6.dfsg.2), libldap-2.4-2 (>= 2.4.7), libpam0g (>= 0.99.7.1), libpq5 (>= 9.1~), libssl1.0.0 (>= 1.0.0), libxml2 (>= 2.7.4), postgresql-client-9.1, postgresql-common (>= 115~), tzdata, ssl-cert, locales Suggests: oidentd | ident-server, locales-all Conflicts: postgresql (<< 7.5) Breaks: postgresql-plpython-9.1 (<< 9.1.6-0ubuntu12.04.1) Filename: pool/main/p/postgresql-9.1/postgresql-9.1_9.1.6-0ubuntu12.04.1_amd64.deb Size: 4298270 MD5sum: 9ee2ab5f25f949121f736ad80d735d57 SHA1: 5eac1cca8d00c4aec4fb55c46fc2a013bc401642 SHA256: 4e6c24c251a01f1b6a340c96d24fdbb92b5e2f8a2f4a8b6b08a0df0fe4cf62ab Description-en: object-relational SQL database, version 9.1 server PostgreSQL is a fully featured object-relational database management system. It supports a large part of the SQL standard and is designed to be extensible by users in many aspects. Some of the features are: ACID transactions, foreign keys, views, sequences, subqueries, triggers, user-defined types and functions, outer joins, multiversion concurrency control. Graphical user interfaces and bindings for many programming languages are available as well. . This package provides the database server for PostgreSQL 9.1. Servers for other major release versions can be installed simultaneously and are coordinated by the postgresql-common package. A package providing ident-server is needed if you want to authenticate remote connections with identd. Homepage: http://www.postgresql.org/ Description-md5: c487fe4e86f0eac09ed9847282436059 Bugs: https://bugs.launchpad.net/ubuntu/+filebug Origin: Ubuntu Supported: 5y Task: postgresql-server Package: postgresql-9.1 Priority: optional Section: database Installed-Size: 11164 Maintainer: Ubuntu Developers <[email protected]> Original-Maintainer: Martin Pitt <[email protected]> Architecture: amd64 Version: 9.1.5-0ubuntu12.04 Replaces: postgresql-contrib-9.1 (<< 9.1~beta1-3~), postgresql-plpython-9.1 (<< 9.1.5-0ubuntu12.04) Depends: libc6 (>= 2.15), libcomerr2 (>= 1.01), libgssapi-krb5-2 (>= 1.8+dfsg), libkrb5-3 (>= 1.6.dfsg.2), libldap-2.4-2 (>= 2.4.7), libpam0g (>= 0.99.7.1), libpq5 (>= 9.1~), libssl1.0.0 (>= 1.0.0), libxml2 (>= 2.7.4), postgresql-client-9.1, postgresql-common (>= 115~), tzdata, ssl-cert, locales Suggests: oidentd | ident-server, locales-all Conflicts: postgresql (<< 7.5) Breaks: postgresql-plpython-9.1 (<< 9.1.5-0ubuntu12.04) Filename: pool/main/p/postgresql-9.1/postgresql-9.1_9.1.5-0ubuntu12.04_amd64.deb Size: 4298028 MD5sum: 3797b030ca8558a67b58e62cc0a22646 SHA1: ad340a9693341621b82b7f91725fda781781c0fb SHA256: 99aa892971976b85bcf6fb2e1bb8bf3e3fb860190679a225e7ceeb8f33f0e84b Description-en: object-relational SQL database, version 9.1 server PostgreSQL is a fully featured object-relational database management system. It supports a large part of the SQL standard and is designed to be extensible by users in many aspects. Some of the features are: ACID transactions, foreign keys, views, sequences, subqueries, triggers, user-defined types and functions, outer joins, multiversion concurrency control. Graphical user interfaces and bindings for many programming languages are available as well. . This package provides the database server for PostgreSQL 9.1. Servers for other major release versions can be installed simultaneously and are coordinated by the postgresql-common package. A package providing ident-server is needed if you want to authenticate remote connections with identd. Homepage: http://www.postgresql.org/ Description-md5: c487fe4e86f0eac09ed9847282436059 Bugs: https://bugs.launchpad.net/ubuntu/+filebug Origin: Ubuntu Supported: 5y Task: postgresql-server Package: postgresql-9.1 Priority: optional Section: database Installed-Size: 11220 Maintainer: Martin Pitt <[email protected]> Original-Maintainer: Martin Pitt <[email protected]> Architecture: amd64 Version: 9.1.3-2 Replaces: postgresql-contrib-9.1 (<< 9.1~beta1-3~), postgresql-plpython-9.1 (<< 9.1.3-2) Depends: libc6 (>= 2.15), libcomerr2 (>= 1.01), libgssapi-krb5-2 (>= 1.8+dfsg), libkrb5-3 (>= 1.6.dfsg.2), libldap-2.4-2 (>= 2.4.7), libpam0g (>= 0.99.7.1), libpq5 (>= 9.1~), libssl1.0.0 (>= 1.0.0), libxml2 (>= 2.7.4), postgresql-client-9.1, postgresql-common (>= 115~), tzdata, ssl-cert, locales Suggests: oidentd | ident-server, locales-all Conflicts: postgresql (<< 7.5) Breaks: postgresql-plpython-9.1 (<< 9.1.3-2) Filename: pool/main/p/postgresql-9.1/postgresql-9.1_9.1.3-2_amd64.deb Size: 4284744 MD5sum: bad9aac349051fe86fd1c1f628797122 SHA1: a3f5d6583cc6e2372a077d7c2fc7adfcfa0d504d SHA256: e885c32950f09db7498c90e12c4d1df0525038d6feb2f83e2e50f563fdde404a Description-en: object-relational SQL database, version 9.1 server PostgreSQL is a fully featured object-relational database management system. It supports a large part of the SQL standard and is designed to be extensible by users in many aspects. Some of the features are: ACID transactions, foreign keys, views, sequences, subqueries, triggers, user-defined types and functions, outer joins, multiversion concurrency control. Graphical user interfaces and bindings for many programming languages are available as well. . This package provides the database server for PostgreSQL 9.1. Servers for other major release versions can be installed simultaneously and are coordinated by the postgresql-common package. A package providing ident-server is needed if you want to authenticate remote connections with identd. Homepage: http://www.postgresql.org/ Description-md5: c487fe4e86f0eac09ed9847282436059 Bugs: https://bugs.launchpad.net/ubuntu/+filebug Origin: Ubuntu Supported: 5y Task: postgresql-server

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• How do I grok NHibernate's QueryOver API?

  - by Brant Bobby

  I've run into the limits of what NHibernate 3.0's LINQ provider is capable of and decided it's time to learn about one of the more powerful (or at least feature-complete) options: the QueryOver API. The problem is, I have zero experience with ICriteria, and all of the tutorials I've been able to find online either: Assume I'm an ICriteria expert and simply show me how to convert ICriteria code to the new fluent interface, or Are trivial "here's how you do an inner join" examples that don't really help me understand more complex concepts like projections, subqueries, requirements, or whatever other magic the API is capable of. What should I read to really learn about QueryOver, and how to make full use of it?

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• Derby 10.9.1.0 released

  - by kah

  Earlier today, the release of Apache Derby 10.9.1.0 was announced. In addition to the usual chunk of bug fixes, this release includes the following new features: NATIVE authentication, a new authentication mechanism with better support for managing credentials. See this section of the developer's guide for an introduction. JDBC 4.1 escape syntax completes Derby's support for JDBC 4.1. Allow multi-column subqueries in EXISTS predicates (SQL:2003 Feature T501, Enhanced EXISTS predicate) to support auto-generated SQL from some persistence frameworks. Download it now and try it out!

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• How do I avoid a repetitive subquery JOIN in SQL?

  - by Karl

  Hi In SQL Server 2008: I have one table, and I want to do something along the following lines: SELECT T1.stuff, T2.morestuff from ( SELECT code, date1, date2 from Table ) as T1 INNER JOIN ( SELECT code, date1, date2 from Table ) as T2 ON T1.code = T2.code and T1.date1 = T2.date2 The two subqueries are exactly identical. Is there any way I can do this without repeating the subquery script? Thanks Karl

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• Optimize the sql query

  - by joseph

  UPDATE employees SET job_id = (SELECT job_id FROM employees WHERE employee_id = 205), salary = (SELECT salary FROM employees WHERE employee_id = 205) WHERE employee_id = 114; This is the query i have been using. Here i use 2 subqueries but they have the same where condition.. The seek time is doubled.. Is there a way to optimize the whole query to a single subquery? Thanks in advance

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• Limiting selected rows count with a stored procedure parameter in MySQL

  - by ssobczak

  I have a procedure SelectProc wich contains SELECT statement. I want to add a procedure param LimitRowsCount and use it as following: CREATE PROCEDURE SelectProc (IN LimitRowsCount INTEGER UNSIGNED) BEGIN SELECT (...) LIMIT LimitRowsCount; END but this approach doesn't work. The SELECT itself contains nested subqueries so I can't create view from it. Is there a way more propper then dynamic SQL (prepared statements) ?

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• Intermittent "Specified cast is invalid" with StructureMap injected data context

  - by FreshCode

  I am intermittently getting an System.InvalidCastException: Specified cast is not valid. error in my repository layer when performing an abstracted SELECT query mapped with LINQ. The error can't be caused by a mismatched database schema since it works intermittently and it's on my local dev machine. Could it be because StructureMap is caching the data context between page requests? If so, how do I tell StructureMap v2.6.1 to inject a new data context argument into my repository for each request? Update: I found this question which correlates my hunch that something was being re-used. Looks like I need to call Dispose on my injected data context. Not sure how I'm going to do this to all my repositories without copypasting a lot of code. Edit: These errors are popping up all over the place whenever I refresh my local machine too quickly. Doesn't look like it's happening on my remote deployment box, but I can't be sure. I changed all my repositories' StructureMap life cycles to HttpContextScoped() and the error persists. Code: public ActionResult Index() { // error happens here, which queries my page repository var page = _branchService.GetPage("welcome"); if (page != null) ViewData["Welcome"] = page.Body; ... } Repository: GetPage boils down to a filtered query mapping in my page repository. public IQueryable<Page> GetPages() { var pages = from p in _db.Pages let categories = GetPageCategories(p.PageId) let revisions = GetRevisions(p.PageId) select new Page { ID = p.PageId, UserID = p.UserId, Slug = p.Slug, Title = p.Title, Description = p.Description, Body = p.Text, Date = p.Date, IsPublished = p.IsPublished, Categories = new LazyList<Category>(categories), Revisions = new LazyList<PageRevision>(revisions) }; return pages; } where _db is an injected data context as an argument, stored in a private variable which I reuse for SELECT queries. Error: Specified cast is not valid. Exception Details: System.InvalidCastException: Specified cast is not valid. Stack Trace: [InvalidCastException: Specified cast is not valid.] System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) +4539 System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) +207 System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) +500 System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute(Expression expression) +50 System.Linq.Queryable.FirstOrDefault(IQueryable`1 source) +383 Manager.Controllers.SiteController.Index() in C:\Projects\Manager\Manager\Controllers\SiteController.cs:68 lambda_method(Closure , ControllerBase , Object[] ) +79 System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +258 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +39 System.Web.Mvc.<>c__DisplayClassd.<InvokeActionMethodWithFilters>b__a() +125 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodFilter(IActionFilter filter, ActionExecutingContext preContext, Func`1 continuation) +640 System.Web.Mvc.ControllerActionInvoker.InvokeActionMethodWithFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +312 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +709 System.Web.Mvc.Controller.ExecuteCore() +162 System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__4() +58 System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +20 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +453 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +371

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• SQL optimization: deletes taking a long time

  - by Will

  I have an Oracle SQL query as part of a stored proc: DELETE FROM item i WHERE NOT EXISTS (SELECT 1 FROM item_queue q WHERE q.n=i.n) AND NOT EXISTS (SELECT 1 FROM tool_queue t WHERE t.n=i.n); A bit about the tables: item contains about 10k rows with an index on the n column item_queue contains about 1mil rows also with index on n column tool_queue contains about 5mil rows indexed as well I am wondering if the query/subqueries can be optimized somehow to make them run faster, I thought that deletes were generally fairly fast

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• SQL Error with Order By in Subquery

  - by cagin

  Hi all. i m working sql server 2005. My query is: SELECT ( SELECT COUNT(1) FROM Seanslar WHERE MONTH(tarihi) = 4 GROUP BY refKlinik_id ORDER BY refKlinik_id) as dorduncuay And the error: The ORDER BY clause is invalid in views, inline functions, derived tables, subqueries, and common table expressions, unless TOP or FOR XML is also specified. How can i use order by in a sub query?

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• MySQL Query For Copying Contents Into Another Field, Same Row

  - by Rob Adler

  Is there a single query (subqueries in it are allowed) where I can copy the content of one field into another field, per row. Example: price, and priceBackup Records: 45.55 47.77 45.55 copies into priceBackup for that specific row, 47.77 copies into priceBackup for that specific row. I do have a primary key, auto increment on it under 'id'. Thanks guys!

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• Alternatives to LIMIT and OFFSET for paging in Oracle

  - by depr001

  Hello, I'm developing a web application and need to page ordered results. I normaly use LIMIT/OFFSET for this purpose. Which is the best way to page ordered results in Oracle? I've seen some samples using rownum and subqueries. Is that the way? Could you give me a sample for translating this SQL to Oracle: SELECT fieldA,fieldB FROM table ORDER BY fieldA OFFSET 5 LIMIT 14 (I'm using Oracle 10g, for what it's worth) Thanks!

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• computed column calculate a value based on different table

  - by adnan

  i've a table c_const code | nvalue -------------- 1 | 10000 2 | 20000 and i've another table t_anytable rec_id | s_id | n_code --------------------- 2 | x | 1 now i want to calculate the x value with computed column, based on rec_id*(select nvalue from c_const where code=ncode) but i get error "Subqueries are not allowed in this context. Only scalar expressions are allowed." how can i calculate the value in this computed column ? thanks.

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• T-SQL Subquery Question

  - by Nick

  Hi, i have two queries. For each tuple of query1 i want to run query2. i dont want to use cursors. i tried several approaches using subqueries. query1: select distinct category, Count(category) as CategoryCount from mytable group by category query2: select top 3 Text, Title, Category from mytable where Category = '1' Category = '1' is a sample. the value should come from query1

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• MySql mutliple tables

  - by Chris Harrison

  I've been looking into JOIN, subqueries and other ways of doing this, but I can't work out the best way to do this is... I have a table (ps_category_product): id_product, id_category I want to perform a query on it like: SELECT id_product FROM ps_category_product WHERE id_category='$this_cat' BUT, I only want to perform this query where the ID's are returned by a query on another table (ps_product): id_product, active SELECT id_product FROM ps_product WHERE active='1' Can anyone help me with getting these two queries working together?

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• How do MySQL views work?

  - by Hello you all men

  When I create a view I am basically like making a new table that will automatically be transacted upon when data in one of the tables it joins changes? Also why can't I use subqueries in my view????

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• Listing common SQL Code Smells.

  - by Phil Factor

  Once you’ve done a number of SQL Code-reviews, you’ll know those signs in the code that all might not be well. These ’Code Smells’ are coding styles that don’t directly cause a bug, but are indicators that all is not well with the code. . Kent Beck and Massimo Arnoldi seem to have coined the phrase in the "OnceAndOnlyOnce" page of www.C2.com, where Kent also said that code "wants to be simple". Bad Smells in Code was an essay by Kent Beck and Martin Fowler, published as Chapter 3 of the book ‘Refactoring: Improving the Design of Existing Code’ (ISBN 978-0201485677) Although there are generic code-smells, SQL has its own particular coding habits that will alert the programmer to the need to re-factor what has been written. See Exploring Smelly Code   and Code Deodorants for Code Smells by Nick Harrison for a grounding in Code Smells in C# I’ve always been tempted by the idea of automating a preliminary code-review for SQL. It would be so useful to trawl through code and pick up the various problems, much like the classic ‘Lint’ did for C, and how the Code Metrics plug-in for .NET Reflector by Jonathan 'Peli' de Halleux is used for finding Code Smells in .NET code. The problem is that few of the standard procedural code smells are relevant to SQL, and we need an agreed list of code smells. Merrilll Aldrich made a grand start last year in his blog Top 10 T-SQL Code Smells.However, I'd like to make a start by discovering if there is a general opinion amongst Database developers what the most important SQL Smells are. One can be a bit defensive about code smells. I will cheerfully write very long stored procedures, even though they are frowned on. I’ll use dynamic SQL occasionally. You can only use them as an aid for your own judgment and it is fine to ‘sign them off’ as being appropriate in particular circumstances. Also, whole classes of ‘code smells’ may be irrelevant for a particular database. The use of proprietary SQL, for example, is only a ‘code smell’ if there is a chance that the database will have to be ported to another RDBMS. The use of dynamic SQL is a risk only with certain security models. As the saying goes,  a CodeSmell is a hint of possible bad practice to a pragmatist, but a sure sign of bad practice to a purist. Plamen Ratchev’s wonderful article Ten Common SQL Programming Mistakes lists some of these ‘code smells’ along with out-and-out mistakes, but there are more. The use of nested transactions, for example, isn’t entirely incorrect, even though the database engine ignores all but the outermost: but it does flag up the possibility that the programmer thinks that nested transactions are supported. If anything requires some sort of general agreement, the definition of code smells is one. I’m therefore going to make this Blog ‘dynamic, in that, if anyone twitters a suggestion with a #SQLCodeSmells tag (or sends me a twitter) I’ll update the list here. If you add a comment to the blog with a suggestion of what should be added or removed, I’ll do my best to oblige. In other words, I’ll try to keep this blog up to date. The name against each 'smell' is the name of the person who Twittered me, commented about or who has written about the 'smell'. it does not imply that they were the first ever to think of the smell! Use of deprecated syntax such as *= (Dave Howard) Denormalisation that requires the shredding of the contents of columns. (Merrill Aldrich) Contrived interfaces Use of deprecated datatypes such as TEXT/NTEXT (Dave Howard) Datatype mis-matches in predicates that rely on implicit conversion.(Plamen Ratchev) Using Correlated subqueries instead of a join   (Dave_Levy/ Plamen Ratchev) The use of Hints in queries, especially NOLOCK (Dave Howard /Mike Reigler) Few or No comments. Use of functions in a WHERE clause. (Anil Das) Overuse of scalar UDFs (Dave Howard, Plamen Ratchev) Excessive ‘overloading’ of routines. The use of Exec xp_cmdShell (Merrill Aldrich) Excessive use of brackets. (Dave Levy) Lack of the use of a semicolon to terminate statements Use of non-SARGable functions on indexed columns in predicates (Plamen Ratchev) Duplicated code, or strikingly similar code. Misuse of SELECT * (Plamen Ratchev) Overuse of Cursors (Everyone. Special mention to Dave Levy & Adrian Hills) Overuse of CLR routines when not necessary (Sam Stange) Same column name in different tables with different datatypes. (Ian Stirk) Use of ‘broken’ functions such as ‘ISNUMERIC’ without additional checks. Excessive use of the WHILE loop (Merrill Aldrich) INSERT ... EXEC (Merrill Aldrich) The use of stored procedures where a view is sufficient (Merrill Aldrich) Not using two-part object names (Merrill Aldrich) Using INSERT INTO without specifying the columns and their order (Merrill Aldrich) Full outer joins even when they are not needed. (Plamen Ratchev) Huge stored procedures (hundreds/thousands of lines). Stored procedures that can produce different columns, or order of columns in their results, depending on the inputs. Code that is never used. Complex and nested conditionals WHILE (not done) loops without an error exit. Variable name same as the Datatype Vague identifiers. Storing complex data  or list in a character map, bitmap or XML field User procedures with sp_ prefix (Aaron Bertrand)Views that reference views that reference views that reference views (Aaron Bertrand) Inappropriate use of sql_variant (Neil Hambly) Errors with identity scope using SCOPE_IDENTITY @@IDENTITY or IDENT_CURRENT (Neil Hambly, Aaron Bertrand) Schemas that involve multiple dated copies of the same table instead of partitions (Matt Whitfield-Atlantis UK) Scalar UDFs that do data lookups (poor man's join) (Matt Whitfield-Atlantis UK) Code that allows SQL Injection (Mladen Prajdic) Tables without clustered indexes (Matt Whitfield-Atlantis UK) Use of "SELECT DISTINCT" to mask a join problem (Nick Harrison) Multiple stored procedures with nearly identical implementation. (Nick Harrison) Excessive column aliasing may point to a problem or it could be a mapping implementation. (Nick Harrison) Joining "too many" tables in a query. (Nick Harrison) Stored procedure returning more than one record set. (Nick Harrison) A NOT LIKE condition (Nick Harrison) excessive "OR" conditions. (Nick Harrison) User procedures with sp_ prefix (Aaron Bertrand) Views that reference views that reference views that reference views (Aaron Bertrand) sp_OACreate or anything related to it (Bill Fellows) Prefixing names with tbl_, vw_, fn_, and usp_ ('tibbling') (Jeremiah Peschka) Aliases that go a,b,c,d,e... (Dave Levy/Diane McNurlan) Overweight Queries (e.g. 4 inner joins, 8 left joins, 4 derived tables, 10 subqueries, 8 clustered GUIDs, 2 UDFs, 6 case statements = 1 query) (Robert L Davis) Order by 3,2 (Dave Levy) MultiStatement Table functions which are then filtered 'Sel * from Udf() where Udf.Col = Something' (Dave Ballantyne) running a SQL 2008 system in SQL 2000 compatibility mode(John Stafford)

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• SQL SERVER – CTRL+SHIFT+] Shortcut to Select Code Between Two Parenthesis

  - by pinaldave

  Every weekend brings creative ideas and accidents brings best unknown secrets in front of us. Just a day while working with complex SQL Server code in SSMS I came across very interesting shortcut which I have never used before and instantly fell in love with it. It is totally possible that you are familiar with this but for me it was the first time and I was surprised that I did know know this short cut so far. Shortcut key is CTRL+SHIFT+]. This key can be very useful when dealing with multiple subqueries, CTE or query with multiple parentheses. When exercised this shortcut key it selects T-SQL code between two parentheses. Let us see the examples to understand the same. In each of the examples I have put the cursor at the position displayed and pressed CTRL+SHIFT+] and it has selected the code between two corresponding parentheses. Cursor position 1 Cursor position 2 Cursor position 3 If you are a developer and have to code with complex queries, you will totally appreciate that this feature can save so much of the time for development. I often remember my experience as a developer when I have lost a lot of hours to just balance parentheses. As I said yesterday I found this shortcut accidently. How many of you were aware of this feature? Is there any other useful feature you would like to share with us? Please leave a comment and if I have not covered it earlier, I will share it due credit on this blog. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology Tagged: SQL Shortcut

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• What relational database system should I learn? [closed]

  - by acidzombie24

  At the moment i know sqlite (my favorite), mysql (its ok, i get annoyed) and i do not want to learn ms/t sql (it only allows one nullable row if the column is unique). I am thinking about learning a new database system. My requirements for it is Must allow multiple connections at once (read and write) All or data i choose must be ACID compliant Performance should be good. I have a 17gb table in one project. It should perform well on read and transactional writes. With mysql it took hours to restore it and there were no foreign keys on that specific table. It only finished in a workday because i found a suggestion to adjust a setting which i think was key-buffer. And it still took hours Unique columns that allow more then one row to be null. I shouldn't have to say it but dammit MS. Allows one to make ongoing backups. Something like 'binary logs'. Some relatively small amounts of data i can grab and apply it to my local db to have it in sync with the one on the server. Table joins. I rather not write a bunch of queries to simulate a join What I would like but is not required Foreign keys. This may be a requirement later Open sourced Fair tool support. So i can measure queries, easily backup/restore, etc .NET and C (or C++) interface. (I seen one that uses raw tcp with JSON which was okish) Good subquery support. Once i was working with an older version of mysql (i believe <5.1 but it could have been 5.1) and i had to write many queries to do one query because it couldn't do subqueries. Or maybe it couldnt do it efficiently and died bc of memory limitations with a huge dataset. What db system should i learn?

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• Django ORM: Ordering w/ aggregate functions — None special treatment

  - by deno

  Hi, I'm doing query like that: SomeObject.objects.annotate(something=Avg('something')).order_by(something).all() Now, I normally have an aggregate field in my model that I use with Django signals to keep in sync, however in this case perfomance isn't an issue so I thought I'd keep it simple and just use subqueries. This approach, however, presented an unexpected issue: It all works grate if aggregate function results are like this: [5.0, 4.0, 6.0 … (etc, just numbers)] However if you mix in some Nones than it's being ordered like this: [None, 5.0, 4.0 …] The issue is that None has higher value than any number, while it should have value at most of 0. I'm using PostgreSQL and haven't tested w/ other DBs. I haven't actually checked what query is generated etc. I worked it around by just sorting in memory: sorted(…, key=lambda _:_.avg_rating if _.avg_rating is not None else 0) So I'm just curious if you know a way to do it w/ just Django ORM. Perhaps .where? or something… Kind regards

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• Devart Oracle Cross Apply Exception

  - by Murilo Amaru Gomes

  I´m running a problem where in one machine the code works and another don´t. Apparently we´re using the same Devart dotConnect for Oracle version (6.80.325.0). The problem is when we have a subquery in the LINQ and we get Cross Apply Not Supported for Oracle. public IQueryable<GE_MENUAPLICACAO> RetornaMenusNegadosParaUsuario2(int seqUsuario, int nroEmpresa) { return from usuarioPerm in entidadesConsinco.GE_USUARIOPERMISSAO from menu in usuarioPerm.GE_ITENSAPP.GE_APLICACAO.GE_MENUAPLICACAOs select menu; } I read a lot about it, and about subqueries, but I really can´t understand why it´s OK in some machines and not OK and another. Did I missed some fix in the installation? Thanks.

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• Complex query in nHibernate using DetachedCriteria

  - by paszczi

  Hello! I'm currently trying to move from hand-crafted hql to queries constructed via DetachedCriteria. I have and HQL: from GenericObject genericObject left join fetch genericObject.Positions positions where (positions.Key.TrackedSourceID, positions.Key.PositionTimestamp) in (select gp.Key.TrackedSourceID, max(gp.Key.PositionTimestamp) from GenericPosition gp group by gp.Key.TrackedSourceID) Now using DetachedCriteria: var subquery = DetachedCriteria .For (typeof (GenericPosition), "gp") .SetProjection (Projections.ProjectionList () .Add (Projections.Property ("gp.Key.TrackedSourceID")) .Add (Projections.Max ("gp.Key.PositionTimestamp")) .Add (Projections.GroupProperty ("gp.Key.TrackedSourceID")) ); var criteriaQuery = DetachedCriteria .For (typeof (GenericObject), "genericObject") .CreateAlias ("genericObject.Positions", "positions") .SetFetchMode ("genericObject.Positions", FetchMode.Eager) .Add (Subqueries.In (??, subquery)) I don't know what to type instead of ?? to create expression like (positions.Key.TrackedSourceID, positions.Key.PositionTimestamp)

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• Nhibernate Criteria Group By clause and select other data that is not grouped

  - by Peter R

  Hi, I have a parent child relationship, let's say class and children. Each child belongs to a class and has a grade. I need to select the children (or the ids of the children) with the lowest grade per class. session.CreateCriteria(typeof(Classs)) .CreateAlias("Children", "children") .SetProjection(Projections.ProjectionList() .Add(Projections.Min("children.Grade")) .Add(Projections.GroupProperty("Id")) ) .List<Object[]>(); This query returns me the lowest grade per class, but I don't know which child got the grade. When I add the children's Id to the group, the group is wrong and every child gets returned. I was hoping we could just select get the id's of those childs without grouping them. If this is not possible, then maybe there is a way to solve this with subqueries?

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• JSINQ (Linq for JavaScript library) sub-queries (how-to)

  - by Tom Tresansky

  I'm using this library: jsinq. I want to create a new object using subqueries. For example, in .NET LINQ, I could do something like this: from a in Attendances where a.SomeProperty = SomeValue select new { .Property1 = a.Property1, .Property2 = a.Property2, .Property3 = (from p in People where p.SomeProperty = a.Property3 select p) } such that I get a list of ALL people where Property3 value matches the attendance's Property3 value in EACH object returned in the list. I didn't see any sample of this in the docs or on the playground. Made a couple tries of it and didn't have any luck. Anybody know if this is possible and how to?

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• How do I insert into a unique key into a table?

  - by Ben McCormack

  I want to insert data into a table where I don't know the next unique key that I need. I'm not sure how to format my INSERT query so that the value of the Key field is 1 greater than the maximum value for the key in the table. I know this is a hack, but I'm just running a quick test against a database and need to make sure I always send over a Unique key. Here's the SQL I have so far: INSERT INTO [CMS2000].[dbo].[aDataTypesTest] ([KeyFld] ,[Int1]) VALUES ((SELECT Max([KeyFld]) FROM [dbo].[aDataTypesTest]) + 1 ,1) which errors out with: Msg 1046, Level 15, State 1, Line 5 Subqueries are not allowed in this context. Only scalar expressions are allowed. I'm not able to modify the underlying database table. What do I need to do to ensure a unique insert in my INSERT SQL code?

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