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  • Why does DateTime to Unix time use a double instead of an integer?

    - by Earlz
    I'm needing to convert a DateTime to a Unix timestamp. So I googled it looking for some example code In just about all the results I see, they use double as the return for such a function, even when explicitly using floor to convert it to an integer. Unix timestamps are always integers. So what problem is there with using either long or int instead of double? static double ConvertToUnixTimestamp(DateTime date) { DateTime origin = new DateTime(1970, 1, 1, 0, 0, 0, 0); TimeSpan diff = date - origin; return Math.Floor(diff.TotalSeconds); }

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  • Linq to SQL DateTime values are local (Kind=Unspecified) - How do I make it UTC?

    - by ericsson007
    Isn't there a (simple) way to tell Linq To SQL classes that a particular DateTime property should be considered as UTC (i.e. having the Kind property of the DateTime type to be Utc by default), or is there a 'clean' workaround? The time zone on my app-server is not the same as the SQL 2005 Server (cannot change any), and none is UTC. When I persist a property of type DateTime to the dB I use the UTC value (so the value in the db column is UTC), but when I read the values back (using Linq To SQL) I get the .Kind property of the DateTime value to be 'Unspecified'. The problem is that when I 'convert' it to UTC it is 4 hours off. This also means that when it is serialized it it ends up on the client side with a 4 hour wrong offset (since it is serialized using the UTC).

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  • Light-weight, free, database query tool for Windows?

    - by NoCatharsis
    My question is very similar to the one here except pertaining to a Windows tool. I am also referencing this table and what I found here with a Google search. However, I have no idea which tool would best meet my (very basic) purposes. I am currently using Excel with a basic ODBC connection string to query my database at work. However, Excel is pretty memory-heavy and a basic query tends to throw my computer into a 30 second stall-a-thon. Is there a free tool out there that is light-weight and can serve the same purpose when provided an ODBC connection and a SQL query? Also would prefer that it easily copies over to a spreadsheet as needed.

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  • Visual Query Builder

    - by johnnyArt
    If been using "dbForge Query Builder" lately and I'm gotten used to the ease of building and testing a query, specially for those complex ones with inner joins, aliases and multiple conditionals. The expiry date of the trial is about to come, and while wanting to remain on the legal side for this I'd rather not pay the 50USD it costs (although I must say it's pretty cheap for what it does). So my question would be: Are there any free alternatives to replace this visual query builder? I've failed to find any and fear that my only two options are paying for it, or going to the dark side.

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  • Query optimization using composite indexes

    - by xmarch
    Many times, during the process of creating a new Coherence application, developers do not pay attention to the way cache queries are constructed; they only check that these queries comply with functional specs. Later, performance testing shows that these perform poorly and it is then when developers start working on improvements until the non-functional performance requirements are met. This post describes the optimization process of a real-life scenario, where using a composite attribute index has brought a radical improvement in query execution times.  The execution times went down from 4 seconds to 2 milliseconds! E-commerce solution based on Oracle ATG – Endeca In the context of a new e-commerce solution based on Oracle ATG – Endeca, Oracle Coherence has been used to calculate and store SKU prices. In this architecture, a Coherence cache stores the final SKU prices used for Endeca baseline indexing. Each SKU price is calculated from a base SKU price and a series of calculations based on information from corporate global discounts. Corporate global discounts information is stored in an auxiliary Coherence cache with over 800.000 entries. In particular, to obtain each price the process needs to execute six queries over the global discount cache. After the implementation was finished, we discovered that the most expensive steps in the price calculation discount process were the global discounts cache query. This query has 10 parameters and is executed 6 times for each SKU price calculation. The steps taken to optimise this query are described below; Starting point Initial query was: String filter = "levelId = :iLevelId AND  salesCompanyId = :iSalesCompanyId AND salesChannelId = :iSalesChannelId "+ "AND departmentId = :iDepartmentId AND familyId = :iFamilyId AND brand = :iBrand AND manufacturer = :iManufacturer "+ "AND areaId = :iAreaId AND endDate >=  :iEndDate AND startDate <= :iStartDate"; Map<String, Object> params = new HashMap<String, Object>(10); // Fill all parameters. params.put("iLevelId", xxxx); // Executing filter. Filter globalDiscountsFilter = QueryHelper.createFilter(filter, params); NamedCache globalDiscountsCache = CacheFactory.getCache(CacheConstants.GLOBAL_DISCOUNTS_CACHE_NAME); Set applicableDiscounts = globalDiscountsCache.entrySet(globalDiscountsFilter); With the small dataset used for development the cache queries performed very well. However, when carrying out performance testing with a real-world sample size of 800,000 entries, each query execution was taking more than 4 seconds. First round of optimizations The first optimisation step was the creation of separate Coherence index for each of the 10 attributes used by the filter. This avoided object deserialization while executing the query. Each index was created as follows: globalDiscountsCache.addIndex(new ReflectionExtractor("getXXX" ) , false, null); After adding these indexes the query execution time was reduced to between 450 ms and 1s. However, these execution times were still not good enough.  Second round of optimizations In this optimisation phase a Coherence query explain plan was used to identify how many entires each index reduced the results set by, along with the cost in ms of executing that part of the query. Though the explain plan showed that all the indexes for the query were being used, it also showed that the ordering of the query parameters was "sub-optimal".  Parameters associated to object attributes with high-cardinality should appear at the beginning of the filter, or more specifically, the attributes that filters out the highest of number records should be placed at the beginning. But examining corporate global discount data we realized that depending on the values of the parameters used in the query the “good” order for the attributes was different. In particular, if the attributes brand and family had specific values it was more optimal to have a different query changing the order of the attributes. Ultimately, we ended up with three different optimal variants of the query that were used in its relevant cases: String filter = "brand = :iBrand AND familyId = :iFamilyId AND departmentId = :iDepartmentId AND levelId = :iLevelId "+ "AND manufacturer = :iManufacturer AND endDate >= :iEndDate AND salesCompanyId = :iSalesCompanyId "+ "AND areaId = :iAreaId AND salesChannelId = :iSalesChannelId AND startDate <= :iStartDate"; String filter = "familyId = :iFamilyId AND departmentId = :iDepartmentId AND levelId = :iLevelId AND brand = :iBrand "+ "AND manufacturer = :iManufacturer AND endDate >=  :iEndDate AND salesCompanyId = :iSalesCompanyId "+ "AND areaId = :iAreaId  AND salesChannelId = :iSalesChannelId AND startDate <= :iStartDate"; String filter = "brand = :iBrand AND departmentId = :iDepartmentId AND familyId = :iFamilyId AND levelId = :iLevelId "+ "AND manufacturer = :iManufacturer AND endDate >= :iEndDate AND salesCompanyId = :iSalesCompanyId "+ "AND areaId = :iAreaId AND salesChannelId = :iSalesChannelId AND startDate <= :iStartDate"; Using the appropriate query depending on the value of brand and family parameters the query execution time dropped to between 100 ms and 150 ms. But these these execution times were still not good enough and the solution was cumbersome. Third and last round of optimizations The third and final optimization was to introduce a composite index. However, this did mean that it was not possible to use the Coherence Query Language (CohQL), as composite indexes are not currently supporte in CohQL. As the original query had 8 parameters using EqualsFilter, 1 using GreaterEqualsFilter and 1 using LessEqualsFilter, the composite index was built for the 8 attributes using EqualsFilter. The final query had an EqualsFilter for the multiple extractor, a GreaterEqualsFilter and a LessEqualsFilter for the 2 remaining attributes.  All individual indexes were dropped except the ones being used for LessEqualsFilter and GreaterEqualsFilter. We were now running in an scenario with an 8-attributes composite filter and 2 single attribute filters. The composite index created was as follows: ValueExtractor[] ve = { new ReflectionExtractor("getSalesChannelId" ), new ReflectionExtractor("getLevelId" ),    new ReflectionExtractor("getAreaId" ), new ReflectionExtractor("getDepartmentId" ),    new ReflectionExtractor("getFamilyId" ), new ReflectionExtractor("getManufacturer" ),    new ReflectionExtractor("getBrand" ), new ReflectionExtractor("getSalesCompanyId" )}; MultiExtractor me = new MultiExtractor(ve); NamedCache globalDiscountsCache = CacheFactory.getCache(CacheConstants.GLOBAL_DISCOUNTS_CACHE_NAME); globalDiscountsCache.addIndex(me, false, null); And the final query was: ValueExtractor[] ve = { new ReflectionExtractor("getSalesChannelId" ), new ReflectionExtractor("getLevelId" ),    new ReflectionExtractor("getAreaId" ), new ReflectionExtractor("getDepartmentId" ),    new ReflectionExtractor("getFamilyId" ), new ReflectionExtractor("getManufacturer" ),    new ReflectionExtractor("getBrand" ), new ReflectionExtractor("getSalesCompanyId" )}; MultiExtractor me = new MultiExtractor(ve); // Fill composite parameters.String SalesCompanyId = xxxx;...AndFilter composite = new AndFilter(new EqualsFilter(me,                   Arrays.asList(iSalesChannelId, iLevelId, iAreaId, iDepartmentId, iFamilyId, iManufacturer, iBrand, SalesCompanyId)),                                     new GreaterEqualsFilter(new ReflectionExtractor("getEndDate" ), iEndDate)); AndFilter finalFilter = new AndFilter(composite, new LessEqualsFilter(new ReflectionExtractor("getStartDate" ), iStartDate)); NamedCache globalDiscountsCache = CacheFactory.getCache(CacheConstants.GLOBAL_DISCOUNTS_CACHE_NAME); Set applicableDiscounts = globalDiscountsCache.entrySet(finalFilter);      Using this composite index the query improved dramatically and the execution time dropped to between 2 ms and  4 ms.  These execution times completely met the non-functional performance requirements . It should be noticed than when using the composite index the order of the attributes inside the ValueExtractor was not relevant.

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  • Problem in HQL query

    - by Rupeshit
    I written a query in my sql like this: "select * from table_name order by col_name = 101 desc " Which is working perfectly fine in mysql but when I tried to convert this query into HQl query then it is throwing an exception.So can anyone suggest me that how to write HQL query for the above SQL query.

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  • SQLAlchemy custom query column

    - by thrillerator
    I have a declarative table defined like this: class Transaction(Base): __tablename__ = "transactions" id = Column(Integer, primary_key=True) account_id = Column(Integer) transfer_account_id = Column(Integer) amount = Column(Numeric(12, 2)) ... The query should be: SELECT id, (CASE WHEN transfer_account_id=1 THEN -amount ELSE amount) AS amount FROM transactions WHERE account_id = 1 OR transfer_account_id = 1 My code is: query = Transaction.query.filter_by(account_id=1, transfer_account_id=1) query = query.add_column(func.case(...).label("amount") But it doesn't replace the amount column. Been trying to do this with for hours and I don't want to use raw SQL.

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  • Getting age in years in a SQL query

    - by Earlz
    Hello I've been tasked with doing a few queries on a large SQL Server 2000 database. The query I'm having trouble with is "find the number of people between ages 20 and 40" How would I do this? My previous query to get a count of everyone looks like this: select count(rid) from people where ... (with the ... being irrelevant conditions). I've googled some but the only thing I've found for calculating age is so large that I don't see how to embed it into a query, or it is a stored procedure which I do not have the permissions to create. Can someone help me with this?

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  • SQL SERVER – Identify Most Resource Intensive Queries – SQL in Sixty Seconds #028 – Video

    - by pinaldave
    During performance tuning conversation the very first question people often ask is what are the queries offending the server or in another word let us identify the queries which are the most resource intensive. The resources are often described as either Memory, CPU or IO. When we talk about the queries the same is applicable for them as well. The query which is doing lots of reads or writes are for sure resource intensive as well query which are taking maximum CPU time. Performance tuning is a very deep subject and we all have our own preference regarding what should be the first step to tuning and what should be looked with the salt of grain. Though there is no denying that a query which uses more resources than what it should be using for sure require tuning. There are many ways to do identify query using intense resources (e.g. Extended events etc) but in this one we will go by simple DMV. There is a small gotcha we all have to remember about usage of DMV is that it only brings back results from existing cache. So if you have a query which is very resource intensive but is not cached or if you have explicitly removed the query from the cache it will be not part of the result returned by this DMV. It is quite possible that a query is aged and removed from the cache if your cache is not huge. If your cache is large you may want to be careful in running this query during business hours as this query itself can be resource intensive. Get Script to identify resource intensive query from Here Related Tips in SQL in Sixty Seconds: SQL SERVER – Find Most Expensive Queries Using DMV Simple Example to Configure Resource Governor – Introduction to Resource Governor SQL SERVER – DMV – sys.dm_exec_query_optimizer_info – Statistics of Optimizer SQL SERVER – Wait Stats – Wait Types – Wait Queues – Day 0 of 28 Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL in Sixty Seconds, SQL Query, SQL Scripts, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Excel

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  • A Better Way To Extract Date From DateTime Columns [SQL Server]

    - by Gopinath
    Quite a long ago I wrote about a SQL Server programming tip on how to extract date part from a DATETIME column. The post discusses about using of T SQL function convert() to get date part. One of the readers of the post, tipped me about a better way of extracting date part and here is the SQL query he sent to us SELECT DateAdd(day, DateDiff(day, 0, getdate()), 0); In clean way this query trims off time part from the DATETIME value. I rate this solution better than the one I wrote long ago as this one does not depend on any string operations. According the commenter, this method is faster compared to the other. What do you say? Thanks Yamo This article titled,A Better Way To Extract Date From DateTime Columns [SQL Server], was originally published at Tech Dreams. Grab our rss feed or fan us on Facebook to get updates from us.

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  • Oracle get previous day records

    - by Phill Pafford
    Ok I think I'm getting the previous year instead of the previous day, but I need to previous day. SELECT TO_DATE(TO_CHAR(CURRENT_DATE, 'YYYY-MM-DD'),'YYYY-MM-DD') - 1 FROM Dual I'm comparing it to a datetime stamp in this format and wish to get all the rows from the previous day. YYYY-MM-DD HH:MM:SS So I'm trying something like this SELECT field,datetime_field FROM database WHERE datetime_field > TO_DATE(TO_CHAR(CURRENT_DATE, 'YYYY-MM-DD'),'YYYY-MM-DD') - 1

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  • How do i pass arbitary date format from C# to sql backend

    - by Jims
    I have a datetime field for the transaction date in the back end. So I am passing that date from front C#.net, in the below format: 2011-01-01 12:17:51.967 to do this I have written: presentation layer: string date = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff", CultureInfo.InvariantCulture); PropertyClass prp=new PropertyClass(); Prp.TransDate=Convert.ToDateTime(date); PropertyClass structure: Public class property { private DateTime transdate; public DateTime TransDate { get { return transdate; } set { transdate = value; } } } From DAL layer passing the TransactionDate like this: Cmd.Parameters.AddWithValue("@TranSactionDate”, SqlDbType.DateTime).value=propertyobj.TransDate; While debugging from presntation layer: string date = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff", CultureInfo.InvariantCulture); in this I am getting correct expected date format, but when debugs goes to this line Prp.TransDate=Convert.ToDateTime(date); again date format changing to 1/1/2011. But my backend sql datefield wants the date paramter 2011-01-01 12:17:51.967 in this format otherwise throwing exception invalid date format. Note: While passing date as string without converting to datetime getting exceptions like: System.Data.SqlTypes.SqlTypeException: SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM. at System.Data.SqlTypes.SqlDateTime.FromTimeSpan(TimeSpan value) at System.Data.SqlTypes.SqlDateTime.FromDateTime(DateTime value) at System.Data.SqlTypes.SqlDateTime..ctor(DateTime value) at System.Data.SqlClient.MetaType.FromDateTime(DateTime dateTime, Byte cb) at System.Data.SqlClient.TdsParser.WriteValue(Object value, MetaType type, Byte scale, Int32 actualLength, Int32 encodingByteSize, Int32 offset, TdsParserStateObject stateObj) at System.Data.SqlClient.TdsParser.TdsExecuteRPC(_SqlRPC[] rpcArray, Int32 timeout, Boolean inSchema, SqlNotificationRequest notificationRequest, TdsParserStateObject stateObj, Boolean isCommandProc)

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  • Query Months help

    - by StealthRT
    Hey all i am in need of some helpful tips/advice on how to go about my problem. I have a database that houses a "signup" table. The date for this table is formated as such: 2010-04-03 00:00:00 Now suppose i have 10 records in this database: 2010-04-03 00:00:00 2010-01-01 00:00:00 2010-06-22 00:00:00 2010-02-08 00:00:00 2010-02-05 00:00:00 2010-03-08 00:00:00 2010-09-29 00:00:00 2010-11-16 00:00:00 2010-04-09 00:00:00 2010-05-21 00:00:00 And i wanted to get each months total registers... so following the example above: Jan = 1 Feb = 2 Mar = 1 Apr = 2 May = 1 Jun = 1 Jul = 0 Aug = 0 Sep = 1 Oct = 0 Nov = 1 Dec = 0 Now how can i use a query to do that but not have to use a query like: WHERE left(date, 7) = '2010-01' and keep doing that 12 times? I would like it to be a single query call and just have it place the months visits into a array like so: do until EOF theMonthArray[0] = "total for jan" theMonthArray[1] = "total for feb" theMonthArray[2] = "total for mar" theMonthArray[3] = "total for apr" ...etc loop I just can not think of a way to do that other than the example i posted with the 12 query called-one for each month. This is my query as of right now. Again, this only populates for one month where i am trying to populate all 12 months all at once. SELECT count(idNumber) as numVisits, theAccount, signUpDate, theActive from userinfo WHERE theActive = 'YES' AND idNumber = '0203' AND theAccount = 'SUB' AND left(signUpDate, 7) = '2010-04' GROUP BY idNumber ORDER BY numVisits; The example query above outputs this: numVisits | theAccount | signUpDate | theActive 2 SUB 2010-04-16 00:00:00 YES Which is correct because i have 2 records within the month of April. But again, i am trying to do all 12 months at one time (in a single query) so i do not tax the database server as much when compared to doing 12 different query's... UPDATE I'm looking to do something like along these lines: if NOT rst.EOF if left(rst("signUpDate"), 7) = "2010-01" then theMonthArray[0] = rst("numVisits") end if if left(rst("signUpDate"), 7) = "2010-02" then theMonthArray[1] = rst("numVisits") end if etc etc.... end if Any help would be great! :) David

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  • I need to calculate the date / time difference between one date time column

    - by Stringz
    Details. I have the notes table having the following columns. ID - INT(3) Date - DateTime Note - VARCHAR(100) Tile - Varchar(100) UserName - Varchar(100) Now this table will be having NOTES along with the Titles entered by UserName on the specified date / time. I need to calculate the DateTimeDifference between the TWO ROWS in the SAME COLUMN For example the above table has this peice of information in the table. 64, '2010-03-26 18:16:13', 'Action History', 'sending to Level 2.', 'Salman Khwaja' 65, '2010-03-26 18:19:48', 'Assigned By', 'This is note one for the assignment of RF.', 'Salman Khwaja' 66, '2010-03-27 19:19:48', 'Assigned By', 'This is note one for the assignment of CRF.', 'Salman Khwaja' Now I need to have the following resultset in query reports using MYSQL. TASK - TIME Taken ACTION History - 2010-03-26 18:16:13 Assigned By - 00:03:35 Assigned By - 25:00:00 More smarter approach would be TASK - TIME Taken ACTION History - 2010-03-26 18:16:13 Assigned By - 3 minutes 35 seconds Assigned By - 1 day, 1 hour. I would appreciate if one could give me the PLAIN QUERY along with PHP code to embed it too.

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  • Is there a way to optimize this mysql query...?

    - by SpikETidE
    Hi Everyone... Say, I got these two tables.... Table 1 : Hotels hotel_id hotel_name 1 abc 2 xyz 3 efg Table 2 : Payments payment_id payment_date hotel_id total_amt comission p1 23-03-2010 1 100 10 p2 23-03-2010 2 50 5 p3 23-03-2010 2 200 25 p4 23-03-2010 1 40 2 Now, I need to get the following details from the two tables Given a particular date (say, 23-03-2010), the sum of the total_amt for each of the hotel for which a payment has been made on that particular date. All the rows that has the date 23-03-2010 ordered according to the hotel name A sample output is as follows... +------------+------------+------------+---------------+ | hotel_name | date | total_amt | commission | +------------+------------+------------+---------------+ | * abc | 23-03-2010 | 140 | 12 | +------------+------------+------------+---------------+ |+-----------+------------+------------+--------------+| || paymt_id | date | total_amt | commission || |+-----------+------------+------------+--------------+| || p1 | 23-03-2010 | 100 | 10 || |+-----------+------------+------------+--------------+| || p4 | 23-03-2010 | 40 | 2 || |+-----------+------------+------------+--------------+| +------------+------------+------------+---------------+ | * xyz | 23-03-2010 | 250 | 30 | +------------+------------+------------+---------------+ |+-----------+------------+------------+--------------+| || paymt_id | date | total_amt | commission || |+-----------+------------+------------+--------------+| || p2 | 23-03-2010 | 50 | 5 || |+-----------+------------+------------+--------------+| || p3 | 23-03-2010 | 200 | 25 || |+-----------+------------+------------+--------------+| +------------------------------------------------------+ Above the sample of the table that has to be printed... The idea is first to show the consolidated detail of each hotel, and when the '*' next to the hotel name is clicked the breakdown of the payment details will become visible... But that can be done by some jquery..!!! The table itself can be generated with php... Right now i am using two separate queries : One to get the sum of the amount and commission grouped by the hotel name. The next is to get the individual row for each entry having that date in the table. This is, of course, because grouping the records for calculating sum() returns only one row for each of the hotel with the sum of the amounts... Is there a way to combine these two queries into a single one and do the operation in a more optimized way...?? Hope i am being clear.. Thanks for your time and replies...

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  • MS Query returns data inside itself but does not export it to Excel

    - by kappa
    Hi, I'm having a strange problem with Excel and MS Query: I'm using MS Query to run a T-SQL query against a Microsoft SQL Server 2000 and return the results to Excel. To do this, I open Excel, go to Data - Import external data - New database query, select my data source, paste the SQL script in MS Query and click File - Return data to Microsoft Office Excel, leaving all the query options to their defaults. This works fine for many other Excel files, but this time although MS Query shows the correct data when I paste the SQL script, after returning to Excel all I get is the query name in the upper left cell, with no data returned. I fear the cause could be the SQL script, as it contains some advanced functions like union all, UDFs and variables. Here's the script: declare @date smalldatetime set @date = dateadd(day, datediff(day, 0, getdate()), 0) select [date], sum([hours]) as [hours] from ( select [date], [hours] from [server].[dbo].[udf] (84, '2010-01-01', @date) union all select [date], [hours] from [server].[dbo].[udf] (89, '2010-01-01', @date) union all select [date], [hours] from [server].[dbo].[udf] (93, '2010-01-01', @date) ) as [a] group by [date] order by [date] asc I can't get rid of the UDF as inside them are done advanced groupings involving cursors and temporary tables, nor I can remove the variable as the UDF won't accept dateadd(day, datediff(day, 0, getdate()), 0) as parameter. Any ideas? Thanks in advance, Andrea.

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  • Is there a word or description for this type of query?

    - by Nick
    We have the requirement to find a result in a collection of records based on a prioritised set of search criteria against a relational db (I'm talking indexed field matching here rather than text search). The way we are thinking about designing the query is to begin with a highly refined and specific set of criteria. If there are no results for this initial query we want to progressively reduce the criteria one by one in order of reducing priority, querying each time such a less specific set of criteria until we find a result we can accept. Alternatively, we have considered starting with a smaller set of criteria and increasing until we have reduced number of results down to the last set. What I would like to know is if an existing term to describe this type of query exists? So that we can look to model our own on existing patterns and use best practice.

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  • SQL SERVER – SQL in Sixty Seconds – 5 Videos from Joes 2 Pros Series – SQL Exam Prep Series 70-433

    - by pinaldave
    Joes 2 Pros SQL Server Learning series is indeed fun. Joes 2 Pros series is written for beginners and who wants to build expertise for SQL Server programming and development from fundamental. In the beginning of the series author Rick Morelan is not shy to explain the simplest concept of how to open SQL Server Management Studio. Honestly the book starts with that much basic but as it progresses further Rick discussing about various advanced concepts from query tuning to Core Architecture. This five part series is written with keeping SQL Server Exam 70-433. Instead of just focusing on what will be there in exam, this series is focusing on learning the important concepts thoroughly. This book no way take short cut to explain any concepts and at times, will go beyond the topic at length. The best part is that all the books has many companion videos explaining the concepts and videos. Every Wednesday I like to post a video which explains something in quick few seconds. Today we will go over five videos which I posted in my earlier posts related to Joes 2 Pros series. Introduction to XML Data Type Methods – SQL in Sixty Seconds #015 The XML data type was first introduced with SQL Server 2005. This data type continues with SQL Server 2008 where expanded XML features are available, most notably is the power of the XQuery language to analyze and query the values contained in your XML instance. There are five XML data type methods available in SQL Server 2008: query() – Used to extract XML fragments from an XML data type. value() – Used to extract a single value from an XML document. exist() – Used to determine if a specified node exists. Returns 1 if yes and 0 if no. modify() – Updates XML data in an XML data type. node() – Shreds XML data into multiple rows (not covered in this blog post). [Detailed Blog Post] | [Quiz with Answer] Introduction to SQL Error Actions – SQL in Sixty Seconds #014 Most people believe that when SQL Server encounters an error severity level 11 or higher the remaining SQL statements will not get executed. In addition, people also believe that if any error severity level of 11 or higher is hit inside an explicit transaction, then the whole statement will fail as a unit. While both of these beliefs are true 99% of the time, they are not true in all cases. It is these outlying cases that frequently cause unexpected results in your SQL code. To understand how to achieve consistent results you need to know the four ways SQL Error Actions can react to error severity levels 11-16: Statement Termination – The statement with the procedure fails but the code keeps on running to the next statement. Transactions are not affected. Scope Abortion – The current procedure, function or batch is aborted and the next calling scope keeps running. That is, if Stored Procedure A calls B and C, and B fails, then nothing in B runs but A continues to call C. @@Error is set but the procedure does not have a return value. Batch Termination – The entire client call is terminated. XACT_ABORT – (ON = The entire client call is terminated.) or (OFF = SQL Server will choose how to handle all errors.) [Detailed Blog Post] | [Quiz with Answer] Introduction to Basics of a Query Hint – SQL in Sixty Seconds #013 Query hints specify that the indicated hints should be used throughout the query. Query hints affect all operators in the statement and are implemented using the OPTION clause. Cautionary Note: Because the SQL Server Query Optimizer typically selects the best execution plan for a query, it is highly recommended that hints be used as a last resort for experienced developers and database administrators to achieve the desired results. [Detailed Blog Post] | [Quiz with Answer] Introduction to Hierarchical Query – SQL in Sixty Seconds #012 A CTE can be thought of as a temporary result set and are similar to a derived table in that it is not stored as an object and lasts only for the duration of the query. A CTE is generally considered to be more readable than a derived table and does not require the extra effort of declaring a Temp Table while providing the same benefits to the user. However; a CTE is more powerful than a derived table as it can also be self-referencing, or even referenced multiple times in the same query. A recursive CTE requires four elements in order to work properly: Anchor query (runs once and the results ‘seed’ the Recursive query) Recursive query (runs multiple times and is the criteria for the remaining results) UNION ALL statement to bind the Anchor and Recursive queries together. INNER JOIN statement to bind the Recursive query to the results of the CTE. [Detailed Blog Post] | [Quiz with Answer] Introduction to SQL Server Security – SQL in Sixty Seconds #011 Let’s get some basic definitions down first. Take the workplace example where “Tom” needs “Read” access to the “Financial Folder”. What are the Securable, Principal, and Permissions from that last sentence? A Securable is a resource that someone might want to access (like the Financial Folder). A Principal is anything that might want to gain access to the securable (like Tom). A Permission is the level of access a principal has to a securable (like Read). [Detailed Blog Post] | [Quiz with Answer] Please leave a comment explain which one was your favorite video as that will help me understand what works and what needs improvement. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology, Video

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  • Using Query Classes With NHibernate

    - by Liam McLennan
    Even when using an ORM, such as NHibernate, the developer still has to decide how to perform queries. The simplest strategy is to get access to an ISession and directly perform a query whenever you need data. The problem is that doing so spreads query logic throughout the entire application – a clear violation of the Single Responsibility Principle. A more advanced strategy is to use Eric Evan’s Repository pattern, thus isolating all query logic within the repository classes. I prefer to use Query Classes. Every query needed by the application is represented by a query class, aka a specification. To perform a query I: Instantiate a new instance of the required query class, providing any data that it needs Pass the instantiated query class to an extension method on NHibernate’s ISession type. To query my database for all people over the age of sixteen looks like this: [Test] public void QueryBySpecification() { var canDriveSpecification = new PeopleOverAgeSpecification(16); var allPeopleOfDrivingAge = session.QueryBySpecification(canDriveSpecification); } To be able to query for people over a certain age I had to create a suitable query class: public class PeopleOverAgeSpecification : Specification<Person> { private readonly int age; public PeopleOverAgeSpecification(int age) { this.age = age; } public override IQueryable<Person> Reduce(IQueryable<Person> collection) { return collection.Where(person => person.Age > age); } public override IQueryable<Person> Sort(IQueryable<Person> collection) { return collection.OrderBy(person => person.Name); } } Finally, the extension method to add QueryBySpecification to ISession: public static class SessionExtensions { public static IEnumerable<T> QueryBySpecification<T>(this ISession session, Specification<T> specification) { return specification.Fetch( specification.Sort( specification.Reduce(session.Query<T>()) ) ); } } The inspiration for this style of data access came from Ayende’s post Do You Need a Framework?. I am sick of working through multiple layers of abstraction that don’t do anything. Have you ever seen code that required a service layer to call a method on a repository, that delegated to a common repository base class that wrapped and ORMs unit of work? I can achieve the same thing with NHibernate’s ISession and a single extension method. If you’re interested you can get the full Query Classes example source from Github.

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  • bind would not work unless allow-query is "any"

    - by adrianTNT
    I have this in /etc/named.conf, I commented the default values and set my own under it. My domain would not load in browser unless I set allow-query to "any", is this OK, what should I edit? If is localhost or 127.0.0.1; 10.0.1.0/24; domain would not load. I tried the 127.. thing because it mentioned it here: http://wiki.mandriva.com/en/Testing:Bind Bind version is 9.7.0-P2-RedHat-9.7.0-5.P2.el6_0.1 OS is CentOS 6.0. options { // listen-on port 53 { 127.0.0.1; }; listen-on port 53 { any; }; //listen-on-v6 port 53 { ::1; }; listen-on-v6 port 53 { any; }; directory "/var/named"; dump-file "/var/named/data/cache_dump.db"; statistics-file "/var/named/data/named_stats.txt"; memstatistics-file "/var/named/data/named_mem_stats.txt"; //allow-query { localhost; }; allow-query { any; }; recursion yes; dnssec-enable yes; dnssec-validation yes; dnssec-lookaside auto; /* Path to ISC DLV key */ bindkeys-file "/etc/named.iscdlv.key"; };

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  • MySQL query cache and PHP variables

    - by Saif Bechan
    I have seen the following statement made about the query cache: // query cache does NOT work $r = mysql_query("SELECT username FROM user WHERE signup_date >= CURDATE()"); // query cache works! $today = date("Y-m-d"); $r = mysql_query("SELECT username FROM user WHERE signup_date >= '$today'"); So the query cache only works on the second query. I was wondering if the query cache will also work on this: define('__TODAY',date("Y-m-d")); $r = mysql_query("SELECT username FROM user WHERE signup_date >= '".__TODAY."'");

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  • ADO.NET Commands and SQL query plans

    - by ingredient_15939
    I've been reading up on query plans and how to minimise duplicate plans being created by SQL Server for the same basic query. For example, if I understand correctly, sending both these query strings will result in 2 different query plans: "SELECT FirstName FROM Members WHERE LastName = 'Lee'" "SELECT FirstName FROM Members WHERE LastName = 'MacGhilleseatheanaich'" Using a stored procedure avoids this, as the query plan is the same, and "LastName" is passed as a variable, eg: CREATE PROCEDURE sp_myStoredProcedure @LastName varchar(100) AS SELECT FirstName FROM Members WHERE LastName = @LastName Go Now, my question is whether the same applies to the Command object (eg. SQLClient.SQLCommand in ADO.NET). The reason I ask is that string parameters don't have a defined max length, as in the code above. Take the following code: MyCmd.CommandText = "SELECT FirstName FROM Members WHERE LastName = @LastName" MyCmd.Parameters.AddWithValue("@LastName", "Lee") Then later: MyCmd.Parameters.Clear() MyCmd.Parameters.AddWithValue("@LastName", "MacGhilleseatheanaich") Since @LastName hasn't been declared to SQL Server as having a defined maximum length, will SQL Server create a new query plan for every different value when I execute the command this way?

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