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  • get n records at a time from a temporary table

    - by Claudiu
    I have a temporary table with about 1 million entries. The temporary table stores the result of a larger query. I want to process these records 1000 at a time, for example. What's the best way to set up queries such that I get the first 1000 rows, then the next 1000, etc.? They are not inherently ordered, but the temporary table just has one column with an ID, so I can order it if necessary. I was thinking of creating an extra column with the temporary table to number all the rows, something like: CREATE TEMP TABLE tmptmp AS SELECT ##autonumber somehow##, id FROM .... --complicated query then I can do: SELECT * FROM tmptmp WHERE autonumber>=0 AND autonumber < 1000 etc... how would I actually accomplish this? Or is there a better way? I'm using Python and PostgreSQL.

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  • Logic: Best way to sample & count bytes of a 100MB+ file

    - by Jami
    Let's say I have this 170mb file (roughly 180 million bytes). What I need to do is to create a table that lists: all 4096 byte combinations found [column 'bytes'], and the number of times each byte combination appeared in it [column 'occurrences'] Assume two things: I can save data very fast, but I can update my saved data very slow. How should I sample the file and save the needed information? Here're some suggestions that are (extremely) slow: Go through each 4096 byte combinations in the file, save each data, but search the table first for existing combinations and update it's values. this is unbelievably slow Go through each 4096 byte combinations in the file, save until 1 million rows of data in a temporary table. Go through that table and fix the entries (combine repeating byte combinations), then copy to the big table. Repeat going through another 1 million rows of data and repeat the process. this is faster by a bit, but still unbelievably slow This is kind of like taking the statistics of the file. NOTE: I know that sampling the file can generate tons of data (around 22Gb from experience), and I know that any solution posted would take a bit of time to finish. I need the most efficient saving process

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  • PHP reporting error. DB verify how to?

    - by iamfab
    Error reporting Notice: Undefined variable: random_chars in wamp\www\php_sandbox\idgen.php on line 21 Call Stack: # Time Memory Function Location 1 0.0045 678928 {main}( ) ..\idgen.php:0 GPB7446 How do I fix this error? Using this code like an automatic unique id generator. How do I connect to DB to verify code is truly unique before allowing it to be assigned to a user creating a new account? Thanks <?php $characters = array( "A","B","E","F","G","H","J","K","M","N","P","R","S","T","W","X","Y","Z"); $keys = array(); while(count($keys) < 3) { $x = mt_rand(0, count($characters)-1); if(!in_array($x, $keys)) { $keys[] = $x; } } foreach($keys as $key){ $random_chars .= $characters[$key];} $randNum = rand(2327,9987); $randLet = rand(2327,9987); echo $random_chars . $randNum; ?>

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  • Many tables for many users?

    - by Seagull
    I am new to web programming, so excuse the ignorance... ;-) I have a web application that in many ways can be considered to be a multi-tenant environment. By this I mean that each user of the application gets their own 'custom' environment, with absolutely no interaction between those users. So far I have built the web application as a 'single user' environment. In other words, I haven't actually done anything to support multi-users, but only worked on the functionality I want from the app. Here is my problem... What's the best way to build a multi-user environment: All users point to the same 'core' backend. In other words, I build the logic to separate users via appropriate SQL queries (eg. select * from table where user='123' and attribute='456'). Each user points to a unique tablespace, which is built separately as they join the system. In this case I would simply generate ALL the relevant SQL tables per user, with some sort of suffix for the user. (eg. now a query would look like 'select * from table_ where attribute ='456'). In short, it's a difference between "select * from table where USER=" and "select * from table_USER".

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  • Three-way full outer join in SQLite

    - by Vince
    I have three tables with a common key field, and I need to join them on this key. Given SQLite doesn't have full outer or right joins, I've used the full outer join without right join technique on Wikipedia with much success. But I'm curious, how would one use this technique to join three tables by a common key? What are the efficiency impacts of this (the current query takes about ten minutes)? Thanks!

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  • In a SQL XDL File, how do I read the waitresource attribute on process nodes which are deadlocking?

    - by skimania
    On SQL Server 2005, I'm getting a deadlock when updating two different keys in the same table. note from below that these two waitresources have the same beginning part, but different ending parts. waitresource="KEY: 6:72057594090487808 (d900ed5a6cc6)" and waitresource="KEY: 6:72057594090487808 (d900fb5261bb)" These two keys are locking, and I need to figure out why. The question: If the values in parenthesis are different, why are the first half of the key's the same? <deadlock-list> <deadlock victim="processffffffff8f5863e8"> <process-list> <process id="processaf02f8" taskpriority="0" logused="0" waitresource="KEY: 6:72057594090487808 (d900fb5261bb)" waittime="2281" ownerId="1370264705" transactionname="user_transaction" lasttranstarted="2010-06-17T00:35:25.483" XDES="0x69453a70" lockMode="U" schedulerid="3" kpid="7624" status="suspended" spid="339" sbid="0" ecid="0" priority="0" transcount="2" lastbatchstarted="2010-06-17T00:35:25.483" lastbatchcompleted="2010-06-17T00:35:25.483" clientapp=".Net SqlClient Data Provider" hostname="RISKBBG_VM" hostpid="5848" loginname="RiskOpt" isolationlevel="read committed (2)" xactid="1370264705" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056"> <executionStack> <frame procname="MKP_RISKDB.dbo.MarketDataCurrentRtUpload" line="14" stmtstart="840" stmtend="1220" sqlhandle="0x03000600005f9d24c8878f00849d00000100000000000000"> UPDATE c WITH (ROWLOCK) SET LastUpdate = t.LastUpdate, Value = t.Value, Source = t.Source FROM MarketDataCurrent c INNER JOIN #TEMPTABLE2 t ON c.MDID = t.mdid; -- Insert new MDID </frame> <frame procname="adhoc" line="1" sqlhandle="0x010006004a58132228bf8d73000000000000000000000000"> MarketDataCurrentBlbgRtUpload </frame> </executionStack> <inputbuf> MarketDataCurrentBlbgRtUpload </inputbuf> </process> <process id="processffffffff8f5863e8" taskpriority="0" logused="0" waitresource="KEY: 6:72057594090487808 (d900ed5a6cc6)" waittime="2281" ownerId="1370264646" transactionname="user_transaction" lasttranstarted="2010-06-17T00:35:25.450" XDES="0x1cb72be8" lockMode="U" schedulerid="5" kpid="1880" status="suspended" spid="287" sbid="0" ecid="0" priority="0" transcount="2" lastbatchstarted="2010-06-17T00:35:25.450" lastbatchcompleted="2010-06-17T00:35:25.450" clientapp=".Net SqlClient Data Provider" hostname="RISKAPPS_VM" hostpid="1424" loginname="RiskOpt" isolationlevel="read committed (2)" xactid="1370264646" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056"> <executionStack> <frame procname="MKP_RISKDB.dbo.MarketDataCurrent_BulkUpload" line="28" stmtstart="1062" stmtend="1720" sqlhandle="0x03000600a28e5e4ef4fd8e00849d00000100000000000000"> UPDATE c WITH (ROWLOCK) SET LastUpdate = getdate(), Value = t.Value, Source = @source FROM MarketDataCurrent c INNER JOIN #MDTUP t ON c.MDID = t.mdid WHERE c.lastUpdate &lt; @updateTime and c.mdid not in (select mdid from MarketData where BloombergTicker is not null and PriceSource like &apos;Live.%&apos;) and c.value &lt;&gt; t.value </frame> <frame procname="adhoc" line="1" stmtstart="88" sqlhandle="0x01000600c1653d0598706ca7000000000000000000000000"> exec MarketDataCurrent_BulkUpload @clearBefore, @source </frame> <frame procname="unknown" line="1" sqlhandle="0x000000000000000000000000000000000000000000000000"> unknown </frame> </executionStack> <inputbuf> (@clearBefore datetime,@source nvarchar(10))exec MarketDataCurrent_BulkUpload @clearBefore, @source </inputbuf> </process> </process-list> <resource-list> <keylock hobtid="72057594090487808" dbid="6" objectname="MKP_RISKDB.dbo.MarketDataCurrent" indexname="PK_MarketDataCurrent" id="lock64ac7940" mode="U" associatedObjectId="72057594090487808"> <owner-list> <owner id="processffffffff8f5863e8" mode="U"/> </owner-list> <waiter-list> <waiter id="processaf02f8" mode="U" requestType="wait"/> </waiter-list> </keylock> <keylock hobtid="72057594090487808" dbid="6" objectname="MKP_RISKDB.dbo.MarketDataCurrent" indexname="PK_MarketDataCurrent" id="lockffffffffb8d2dd40" mode="U" associatedObjectId="72057594090487808"> <owner-list> <owner id="processaf02f8" mode="U"/> </owner-list> <waiter-list> <waiter id="processffffffff8f5863e8" mode="U" requestType="wait"/> </waiter-list> </keylock> </resource-list> </deadlock> </deadlock-list>

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  • what does "out of range" mean?

    - by user329820
    Hi I have checked these statements with mysql and no error will happen and also the out put will be 0 rows BUT my friend checked it and he found an error for SELECT becaouse it is out of range !! IS he correct? thanks CREATE TABLE T1(A INTEGER NULL); SELECT * FROM T1;

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  • How to create multiple inputs in yii + Q&A admin page

    - by user1764357
    In yii, i am developing page for Creating Question with multiple options using forms. So i have two tables Question QuestionId Question optionId Option OptionId Option To create multiple options, option field should be provided with add button so that after clicking add button, it should display new textbox control to get the new option. All these options displayed in a gridview. So can you please help me. I am very new to yii.

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  • Set to null a parent record so that children are removed: howto?

    - by EugeneP
    How to delete a child row (on delete cascade ?) when setting a null value on a parent? Here's the db design. table A [id, b_id_1, b_id_2] table B [id, other fields...] b_id_1 and b_id_2 can be NULL if any of them is null, it means NO B records for corresponding FK (there are 2 of them) so (b_id_1,b_id_2) can be (null,null), (100, null), (null, 100_or_any_other_number) etc How in one SQL query both set b_id_1 or b_id_2 to null and delete all rows from B that have this id? What FK design should be applied to the 2 tables? what foreign keys should be added? A - B (FK_1: A.b_id_1 references B.id, FK_2: A.b_id_2 references B.id) and also B-A (FK_3: B.id references A.b_id_1, FK_4: B.id references A.b_id_2) ? But again, setting an A's b_id_1 or A's b_id_2 to null - will it remove any of B's records? I don't think so. So how to do that?

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  • How to design model for multi-tiered data?

    - by Chris
    Say I have three types of object: Area, Subarea and Topic. I want to be able to display an Area, which is just a list of Subareas and the Topics contained in those Subareas. I never want to be able to display Subareas separately - they're just for breaking up the Topics. Topics can, however, appear in multiple Areas (but probably under the same Subarea). How would I design a model for this? I could use ForeignKey from Topic to Subarea and from Subarea to Area, but it seems unnecessarily complex given that I never want to interact with subareas themselves. Also, none of these objects are ever altered or added to by the user. They're just for me to represent information. Maybe there is a better way to represent it all?

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  • help with delete where not in query

    - by kralco626
    I have a lookup table (##lookup). I know it's bad design because I'm duplicating data, but it speeds up my queries tremendously. I have a query that populates this table insert into ##lookup select distinct col1,col2,... from table1...join...etc... I would like to simulate this behavior: delete from ##lookup insert into ##lookup select distinct col1,col2,... from table1...join...etc... This would clearly update the table correctly. But this is a lot of inserting and deleting. It messes with my indexes and locks up the table for selecting from. This table could also be updated by something like: delete from ##lookup where not in (select distinct col1,col2,... from table1...join...etc...) insert into ##lookup (select distinct col1,col2,... from table1...join...etc...) except if it is already in the table The second way may take longer, but I can say "with no lock" and I will be able to select from the table. Any ideas on how to write the query the second way?

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  • MySQL Limiting a query to one consistent value

    - by Lucas Matos
    My current query returns a table like: +------------+ value1 | .... value1 | .... value2 | .... value3 | .... +------------+ I want: +------------+ value1 | .... value1 | .... +------------+ I want to only receive all rows with the first value. Normally I would do a WHERE clause if I knew that value, and I cannot use a LIMIT because each value has a different number of rows. Right now My query looks like "SELECT u.*, n.something, w.* FROM ... AS u, ... AS n, ... AS w WHERE u.id = n.id AND w.val = n.val AND u.desc LIKE '%GET REQUEST VARIABLE%';" This works great, except I get way too many rows and using PHP to do this ruins code portability and is superfluous. Thanks for reading

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  • How SqlDataAdapter works internally?

    - by tigrou
    I wonder how SqlDataAdapter works internally, especially when using UpdateCommand for updating a huge DataTable (since it's usually a lot faster that just sending sql statements from a loop). Here is some idea I have in mind : It creates a prepared sql statement (using SqlCommand.Prepare()) with CommandText filled and sql parameters initialized with correct sql types. Then, it loops on datarows that need to be updated, and for each record, it updates parameters values, and call SqlCommand.ExecuteNonQuery(). It creates a bunch of SqlCommand objects with everything filled inside (CommandText and sql parameters). Several SqlCommands at once are then batched to the server (depending of UpdateBatchSize). It uses some special, low level or undocumented sql driver instructions that allow to perform an update on several rows in a effecient way (rows to update would need to be provided using a special data format and a the same sql query (UpdateCommand here) would be executed against each of these rows).

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  • When/Why to use Cascading in SQL Server?

    - by Joel Coehoorn
    When setting up foreign keys in SQL Server, under what circumstances should you have it cascade on delete or update, and what is the reasoning behind it? This probably applies to other databases as well. I'm looking most of all for concrete examples of each scenario, preferably from someone who has used them successfully.

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  • What is the best way to restore(rollback) data in an application to a specified state(date) ?

    - by panzerschreck
    Hello, An example would set the context right, the example below captures the various states of the entity, which needs to be reverted(rolled back) . State 1 - Recorded on 01-Mar-2010 Column1 Column2 Data1 0.56 State 2 - Recorded on 02-Mar-2010 Column1 Column2 Data1 0.57 State 3 - Recorded on 03-Mar-2010 Column1 Column2 Data1 0.58 User notices that state3 is not what he intended to be in, decides to revert back to state2. One approach that I can think of, without modifying the entity is via "auditing" all the inserts/updates, as below, the rollback information captures the data just before the updates/modifications on the entity, so that it can be applied in an order when you need to revert.Please note that changing the entity's schema, is not an option. Rollback - R1 recorded on 01-Mar-2010 Column1 Column2 Data1 0.56 Rollback - R2 Recorded on 02-Mar-2010 Column1 Column2 Data1 0.56 Rollback - R3 Recorded on 03-Mar-2010 Column1 Column2 Data1 0.57 So, to get to state2 , we would start with rollback information R1,apply R2 onto it. Is there a better approach to achieve this ? Thanks for your time.

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  • Should I Use GUID or IDENTITY as Thread Number?

    - by user311509
    offerID is the thread # which represents the thread posted. I see in forums posts are represented by random numbers. Is this achieved by IDENTITY? If not, please advice. nvarchar(max) will carry all kind of texts along with HTML tags. CREATE TABLE Offer ( offerID int IDENTITY (4382,15) PRIMARY KEY, memberID int NOT NULL REFERENCES Member(memberID), title nvarchar(200) NOT NULL, thread nvarchar(max) NOT NULL, . . . );

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  • How do you write a recursive stored procedure

    - by Grayson Mitchell
    I simply want a stored procedure that calculates a unique id and inserts it. If it fails it just calls itself to regenerate said id. I have been looking for an example, but cant find one, and am not sure how I should get the sp to call itself, and set the appropriate output parameter. I would also appreciate someone pointing out how to test this sp also. ALTER PROCEDURE [dbo].[DataContainer_Insert] @SomeData varchar(max), @DataContainerId int out AS BEGIN -- SET NOCOUNT ON added to prevent extra result sets from -- interfering with SELECT statements. SET NOCOUNT ON; BEGIN TRY SELECT @UserId = MAX(UserId) From DataContainer INSERT INTO DataContainer (UserId, SomeData) VALUES (@UserId, SomeData) SELECT @DataContainerId = scope_identity() END TRY BEGIN CATCH --try again exec DataContainer_Insert @DataContainerId, @SomeData END CATCH END

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  • extract transform load

    - by mitch
    Wikipedia defines a 'typical' ETL cycle as : Cycle initiation Build reference data Extract (from sources) Validate Transform (clean, apply business rules, check for data integrity, create aggregates or disaggregates) Stage (load into staging tables, if used) Audit reports (for example, on compliance with business rules. Also, in case of failure, helps to diagnose/repair) Publish (to target tables) Archive Clean up ..What is meant by 'Build reference data'?

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  • using dummy row with NOT NULL to solve DEFAUT NULL

    - by Tony38
    I know having DEFAULT NULLS is not a good practice but I have many optional lookup values which are FK in the system so to solve this issue here is what i am doing: I use NOT NULL for every FK / lookup valve field. I have the first row in every table which is PK id = 1 as a dummy row with just "none" in all the columns. this way I can use NOT NULL in my schema and if needed reference to the none row values which should be null. Is this a good design or any other work arounds?

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