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  • Database table schema design - varchar(n). Suitable choice of N

    - by morpheous
    Coming from a C background, I may be getting too anal about this and worrying unnecessarily about bits and bytes here. Still, I cant help thinking how the data is actually stored and that if I choose an N which is easily factorizable into a power of 2, the database will be more effecient in how it packs data etc. Using this "logic", I have a string field in a table which is a variable length up to 21 chars. I am tempted to use 32 instead of 21, for the reason given above - however now I am thinking that I am wasting disk space because there will be space allocated for 11 extra chars that are guaranteed to be never used. Since I envisage storing several tens of thousands of rows a day, it all adds up. Question: Mindful of all of the above, Should I declare varchar(21) or varchar(32) and why?

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  • Updating counters through Hibernate

    - by at
    This is an extremely common situation, so I'm expecting a good solution. Basically we need to update counters in our tables. As an example a web page visit: Web_Page -------- Id Url Visit_Count So in hibernate, we might have this code: webPage.setVisitCount(webPage.getVisitCount()+1); The problem there is reads in mysql by default don't pay attention to transactions. So a highly trafficked webpage will have inaccurate counts. The way I'm used to doing this type of thing is simply call: update Web_Page set Visit_Count=Visit_Count+1 where Id=12345; I guess my question is, how do I do that in Hibernate? And secondly, how can I do an update like this in Hibernate which is a bit more complex? update Web_Page wp set wp.Visit_Count=(select stats.Visits from Statistics stats where stats.Web_Page_Id=wp.Id) + 1 where Id=12345;

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  • PHP or JS to connect with fingerprint scanner save to database

    - by narong
    I have a project to set profile user and save all data to database include fingerprint also. i don't what i should start, I have USB finger scanner already to test. What i think: i should have a input box to read data from USB finger scanner than i should create a function to upload it database. but with this thinking i meet problem: i don't know data that get from USB finger scanner is image or data? if image, how i can read it to input box to save to database ? Anyone have any idea, please share me to resolve it. I am looking to see your helping soon! thanks

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  • LinqtoSql Pre-compile Query problem with Count() on a group by

    - by Joe Pitz
    Have a LinqtoSql query that I now want to precompile. var unorderedc = from insp in sq.Inspections where insp.TestTimeStamp > dStartTime && insp.TestTimeStamp < dEndTime && insp.Model == "EP" && insp.TestResults != "P" group insp by new { insp.TestResults, insp.FailStep } into grp select new { FailedCount = (grp.Key.TestResults == "F" ? grp.Count() : 0), CancelCount = (grp.Key.TestResults == "C" ? grp.Count() : 0), grp.Key.TestResults, grp.Key.FailStep, PercentFailed = Convert.ToDecimal(1.0 * grp.Count() / tcount * 100) }; I have created this delegate: public static readonly Funct<SQLDataDataContext, int, string, string, DateTime, DateTime, IQueryable<CalcFailedTestResult>> GetInspData = CompiledQuery.Compile((SQLDataDataContext sq, int tcount, string strModel, string strTest, DateTime dStartTime, DateTime dEndTime, IQueryable<CalcFailedTestResult> CalcFailed) => from insp in sq.Inspections where insp.TestTimeStamp > dStartTime && insp.TestTimeStamp < dEndTime && insp.Model == strModel && insp.TestResults != strTest group insp by new { insp.TestResults, insp.FailStep } into grp select new { FailedCount = (grp.Key.TestResults == "F" ? grp.Count() : 0), CancelCount = (grp.Key.TestResults == "C" ? grp.Count() : 0), grp.Key.TestResults, grp.Key.FailStep, PercentFailed = Convert.ToDecimal(1.0 * grp.Count() / tcount * 100) }); The syntax error is on the CompileQuery.Compile() statement It appears to be related to the use of the select new {} syntax. In other pre-compiled queries I have written I have had to just use the select projection by it self. In this case I need to perform the grp.count() and the immediate if logic. I have searched SO and other references but cannot find the answer.

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  • Do partitions allow multiple bulk loads?

    - by ck
    I have a database that contains data for many "clients". Currently, we insert tens of thousands of rows into multiple tables every so often using .Net SqlBulkCopy which causes the entire tables to be locked and inaccessible for the duration of the transaction. As most of our business processes rely upon accessing data for only one client at a time, we would like to be able to load data for one client, while updating data for another client. To make things more fun, all PKs, FKs and clustered indexes are on GUID columns (I am looking at changing this). I'm looking at adding the ClientID into all tables, then partitioning on this. Would this give me the functionality I require?

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  • Speeding up a group by date query on a big table in postgres

    - by zaius
    I've got a table with around 20 million rows. For arguments sake, lets say there are two columns in the table - an id and a timestamp. I'm trying to get a count of the number of items per day. Here's what I have at the moment. SELECT DATE(timestamp) AS day, COUNT(*) FROM actions WHERE DATE(timestamp) >= '20100101' AND DATE(timestamp) < '20110101' GROUP BY day; Without any indices, this takes about a 30s to run on my machine. Here's the explain analyze output: GroupAggregate (cost=675462.78..676813.42 rows=46532 width=8) (actual time=24467.404..32417.643 rows=346 loops=1) -> Sort (cost=675462.78..675680.34 rows=87021 width=8) (actual time=24466.730..29071.438 rows=17321121 loops=1) Sort Key: (date("timestamp")) Sort Method: external merge Disk: 372496kB -> Seq Scan on actions (cost=0.00..667133.11 rows=87021 width=8) (actual time=1.981..12368.186 rows=17321121 loops=1) Filter: ((date("timestamp") >= '2010-01-01'::date) AND (date("timestamp") < '2011-01-01'::date)) Total runtime: 32447.762 ms Since I'm seeing a sequential scan, I tried to index on the date aggregate CREATE INDEX ON actions (DATE(timestamp)); Which cuts the speed by about 50%. HashAggregate (cost=796710.64..796716.19 rows=370 width=8) (actual time=17038.503..17038.590 rows=346 loops=1) -> Seq Scan on actions (cost=0.00..710202.27 rows=17301674 width=8) (actual time=1.745..12080.877 rows=17321121 loops=1) Filter: ((date("timestamp") >= '2010-01-01'::date) AND (date("timestamp") < '2011-01-01'::date)) Total runtime: 17038.663 ms I'm new to this whole query-optimization business, and I have no idea what to do next. Any clues how I could get this query running faster?

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  • What is the difference between check and foreign key?

    - by GigaPr
    Hi, i am quite confused about the difference between a FOREIGN KEY and CHECK constraint. they appear to me to achieve the same result. I mean I could create a table and enforce a Foreign key on another table, but i could create a CHECK to ensure the value in in another table. What is the difference and when to use the one or the other? thanks

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  • How do I get the earlist DateTime of a set, where there is a few conditions

    - by radbyx
    Create script for Product SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO SET ANSI_PADDING ON GO CREATE TABLE [dbo].[Product]( [ProductID] [int] IDENTITY(1,1) NOT NULL, [ProductName] [varchar](50) NOT NULL, CONSTRAINT [PK_Products] PRIMARY KEY CLUSTERED ( [ProductID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO SET ANSI_PADDING OFF GO Create script for StateLog SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[StateLog]( [StateLogID] [int] IDENTITY(1,1) NOT NULL, [ProductID] [int] NOT NULL, [Status] [bit] NOT NULL, [TimeStamp] [datetime] NOT NULL, CONSTRAINT [PK_Uptime] PRIMARY KEY CLUSTERED ( [StateLogID] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[StateLog] WITH CHECK ADD CONSTRAINT [FK_Uptime_Products] FOREIGN KEY([ProductID]) REFERENCES [dbo].[Product] ([ProductID]) GO ALTER TABLE [dbo].[StateLog] CHECK CONSTRAINT [FK_Uptime_Products] GO I have this and it's not enough: select top 5 [ProductName], [TimeStamp] from [Product] inner join StateLog on [Product].ProductID = [StateLog].ProductID where [Status] = 0 order by TimeStamp desc; (My query givess the 5 lastest TimeStamp's where Status is 0(false).) But I need a thing more: Where there is a set of lastest TimeStamps for a product where Status is 0, i only want the earlist of them (not the lastet). Example: Let's say for Product X i have: TimeStamp1(status = 0) TimeStamp2(status = 1) TimeStamp3(status = 0) TimeStamp4(status = 0) TimeStamp5(status = 1) TimeStamp6(status = 0) TimeStamp7(status = 0) TimeStamp8(status = 0) Correct answer would then be:: TimeStamp6, because it's the first of the lastest timestamps.

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  • Join with table and sub query in oracle

    - by Amandeep
    I dont understand what is wrong with this query it is giving me compile time error of command not ended properly.The inner query is giving me 4 records can any body help me out. select WGN3EVENTPARTICIPANT.EVENTUID from (Select WGN_V_ADDRESS_1.ADDRESSUID1 as add1, WGN_V_ADDRESS_1.ADDRESSUID2 as add2 from WGN3USER inner join WGN_V_ADDRESS_1 on WGN_V_ADDRESS_1.USERID=wgn3user.USERID where WGN3USER.USERNAME='FIRMWIDE\khuraj' ) as ta ,WGN3EVENTPARTICIPANT where (ta.ADDRESSUID1=WGN3EVENTPARTICIPANT.ADDRESSUID1) AND (ta.ADDRESSUID2=WGN3EVENTPARTICIPANT.ADDRESSUID2) I am running it in oracle. Thanks Amandeep

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  • WHERE condition accross multiple rows

    - by Chris G
    I have this table... -------------------------------------- | user_id | status | status_date | -------------------------------------- | 1 | Current | 2012-08-01 | | 1 | Referral | 2012-03-14 | | 2 | Referral | 2012-04-23 | | | | | -------------------------------------- How would I query to find a distinct user_id who has a referral date before 2012-06-30 AND either a current date of after 2012-06-30 or no current status record at all? Database is MySQL.

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  • Help with query in Microsoft Access

    - by Gold
    I have 2 tables: Table A: code | name Table B: barcode | name Table B has full barcode and name, Table A has only code. I need to run update query that fill name in Table A. I tried something like: update A set name = (select top 1 Name from B where B.Code = mid(A.Barcode,1,8)) but it doesn't work.

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  • what does select @@identity do?

    - by every_answer_gets_a_point
    i am connecting to a mysql database through excel using odbc what does this line do? Set rs = oConn.Execute("SELECT @@identity", , adCmdText) i am having trouble updating the database: With rs .AddNew ' create a new record ' add values to each field in the record .Fields("datapath") = dpath .Fields("analysistime") = atime .Fields("reporttime") = rtime .Fields("lastcalib") = lcalib .Fields("analystname") = aname .Fields("reportname") = rname .Fields("batchstate") = "bstate" .Fields("instrument") = "NA" .Update ' stores the new record End With it is ONLY updating .Fields("instrument") = "NA", but for all other fields it is putting NULL values

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  • SQL query construction - separate data in a column into two columns

    - by Tommy
    I have a column that contains links. The problem is that the titles of the links are in the same column, so it looks like this: linktitle|-|linkurl I want link title and linkurl in separate columns. I've created a new column for the urls, so I'm looking for a way to extract them and update the linkurl column with them. Is there any clever way to construct a query that does this?

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  • SQLite: Simple DELETE statement did not work

    - by user186446
    I have a table MRU, that has 3 columns. (VALUE varchar(255); TYPE varchar(20); DT_ADD datetime) This is a table simply storing an entry and recording the date time it was recorded. What I wanted to do is: delete the oldest entry whenever I add a new entry that exceeds a certain number. here is my query: delete from MRU where type = 'FILENAME' ORDER BY DT_ADD limit 1; The query returns an error. Thanks

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  • An attempt to attach an auto-named database for file failed in Vb.Net

    - by user2454135
    I am Trying to connect database for first time , and I am getting this error : An attempt to attach an auto-named database for file VBTestDB.mdf failed. A database with the same name exists, or specified file cannot be opened, or it is located on UNC share. and getting error on myconnect.Open() Heres my code : Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim myconnect As New SqlClient.SqlConnection myconnect.ConnectionString = "Data Source=.\SQLEXPRESS;AttachDbFilename=VBTestDB.mdf;Integrated Security=True;User Instance=True;" Dim mycommand As SqlClient.SqlCommand = New SqlClient.SqlCommand() mycommand.Connection = myconnect mycommand.CommandText = "INSERT INTO Card (CardNo,Name) VALUES (@cardno,@name)" myconnect.Open() Try mycommand.Parameters.Add("@cardno", SqlDbType.Int).Value = TextBox1.Text mycommand.Parameters.Add("@name", SqlDbType.NVarChar).Value = TextBox2.Text mycommand.ExecuteNonQuery() MsgBox("Success") Catch ex As System.Data.SqlClient.SqlException MsgBox(ex.Message) End Try myconnect.Close() End Sub

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  • Insert into select and update in single query

    - by Ossi
    I have 4 tables: tempTBL, linksTBL and categoryTBL, extra on my tempTBL I have: ID, name, url, cat, isinserted columns on my linksTBL I have: ID, name, alias columns on my categoryTBL I have: cl_id, link_id,cat_id on my extraTBL I have: id, link_id, value How do I do a single query to select from tempTBL all items where isinsrted = 0 then insert them to linksTBL and for each record inserted, pickup ID (which is primary) and then insert that ID to categoryTBL with cat_id = 88. after that insert extraTBL ID for link_id and url for value. I know this is so confusing, put I'll post this anyhow... This is what I have so far: INSERT IGNORE INTO linksTBL (link_id,link_name,alias) VALUES(NULL,'tex2','hello'); # generate ID by inserting NULL INSERT INTO categoryTBL (link_id,cat_id) VALUES(LAST_INSERT_ID(),'88'); # use ID in second table I would like to add here somewhere that it only selects items where isinserted = 0 and iserts those records, and onse inserted, will change isinserted to 1, so when next time it runs, it will not add them again.

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  • joining two tables and getting aggregate data

    - by alex
    how do i write a query that returns aggregate sales data for California in the past x months. ----------------------- ----------------------- | order | | customer | |-----------------------| |-----------------------| | orderId int | | customerId int | | customerId int | | state varchar | | deposit decimal | ----------------------- | orderDate date | ----------------------- ----------------------- | orderItem | |-----------------------| | orderId int | | itemId int | | qty int | | lineTotal decimal | | itemPrice decimal | -----------------------

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  • How to login users that are stored within a Wordpress account

    - by user3716795
    I am developing an iOS app that is password protected and all the users are stored in a wordpress account that, of course, is password protected as well. Does anybody know the format that wordpress uses to store login information for these accounts, I would assume that it is a MySQL that sends a json? I have only been able to find the database code for the initial admin page but nothing that shows the way these accounts (815 to be exact) would be stored within the site.

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  • user_objects oracle

    - by mysticfalls
    I would just like to ask what is the difference between user_constraints and user_objects. I have this two database. I run a script on both DB that resulted a unique constraint error. To solve the problem I delete the constraint on user_constraint table for both DB. After that DB1 run without error.. DB2 however failed, I checked the user_constraint for both db and the constraints was deleted. I was asked to check the user_objects.. and found that DB2 has that same constraint_name as the object_name in user_objects table.. Any info regarding their relationship, use, similarites, etc will be appreciated ... Thanks..

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  • Problem with sending "SetCookie" first in php code

    - by Camran
    According to this manual: http://us2.php.net/setcookie I have to set the cookie before anything else. Here is my cookie code: if (isset($_COOKIE['watched_ads'])){ $expir = time()+1728000; //20 days $ad_arr = unserialize($_COOKIE['watched_ads']); $arr_elem = count($ad_arr); if (in_array($ad_id, $ad_arr) == FALSE){ if ($arr_elem>10){ array_shift($ad_arr); } $ad_arr[]=$ad_id; setcookie('watched_ads', serialize($ad_arr), $expir, '/'); } } else { $expir = time()+1728000; //20 days $ad_arr[] = $ad_id; setcookie('watched_ads', serialize($ad_arr), $expir, '/'); } As you can see I am using variables in setting the cookie. The variables comes from a mysql_query and I have to do the query first. But then, if I do, I will get an error message: Cannot modify header information - headers already sent by ... The error points to the line where I set the cookie above. What should I do?a

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  • comparing rows on a mysql table

    - by user311324
    Ok here's the deal I got one table with a bunch of client information. Each client makes up to one purchase a year which is represented by an individual row. there's a column for the year and there's a column the contains a unique identifier for each client. What I need to do is to construct a query that takes last year and this year and shows me which clients were here made a purchase last year but not make a purchase this year. I also need to build a query that shows me which clients did not make a purchase last year and the year before last but did make a purchase this year.

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  • Multiple LIKE, OR MySql Queries Match

    - by Codex73
    Search for: 'chemist' Problem: query which will match a string like 'onechemist' but not 'chemist'. SELECT id,name FROM `records` WHERE name LIKE '%". mysql_real_escape_string($q) ."%' This alternate try won't work: SELECT id,name FROM `records` WHERE name LIKE '%". mysql_real_escape_string($q) ."%' OR name LIKE '". mysql_real_escape_string($q) ."%' OR name LIKE '%". mysql_real_escape_string($q) ."' How could I compile the above into one single query that will match any field which has the string or optimize the query into a better expression?

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  • how to get an xml in a variable

    - by sam
    I have a stored procedure that will return xml. I have delared a variable of type xml and trying to execute the following code declare @v xml set @v = execute get_xml @id, 33 whereas id is returned by another query. now it keeps compalinng about the following error Incorrect syntax near the keyword 'execute'.

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