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  • Which MySql line is faster:

    - by Camran
    I have a classified_id variable which matches one document in a MySql table. I am currently fetching the information about that one record like this: SELECT * FROM table WHERE table.classified_id = $classified_id I wonder if there is a faster approach, for example like this: SELECT 1 FROM table WHERE table.classified_id = $classified_id Wont the last one only select 1 record, which is exactly what I need, so that it doesn't have to scan the entire table but instead stops searching for records after 1 is found? Or am I dreaming this? Thanks

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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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  • Evaluate column value into rows

    - by Hugo Palma
    I have a column whose value is a json array. For example: [{"att1": "1", "att2": "2"}, {"att1": "3", "att2": "4"}, {"att1": "5", "att2": "6"}] What i would like is to provide a view where each element of the json array is transformed into a row and the attributes of each json object into columns. Keep in mind that the json array doesn't have a fixed size. Any ideas on how i can achieve this ?

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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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  • MySQL foreign key constraint disappearing

    - by Bramjam
    This is my table: /* oefenreeks leerplan */ CREATE TABLE leerplan_oefenreeks ( leerplan_oefenreeks_id INT PRIMARY KEY AUTO_INCREMENT NOT NULL, leerplan_id INT NOT NULL, oefenreeks_id INT NOT NULL, plaats INT NOT NULL ); /* fk */ ALTER TABLE leerplan_oefenreeks ADD CONSTRAINT fk_leerp_oefenr_leerplan FOREIGN KEY(leerplan_id) REFERENCES leerplan (leerplan_id) ON DELETE CASCADE; ALTER TABLE leerplan_oefenreeks ADD CONSTRAINT fk_leerp_oefenr_oefenreeks FOREIGN KEY(oefenreeks_id) REFERENCES oefenreeks (oefenreeks_id) ON DELETE CASCADE; /* when I execute the nexline, my fk_leerp_oefenr_leerplan constraint vanishes/disappears*/ ALTER TABLE leerplan_oefenreeks ADD CONSTRAINT un_leerp_oefenr UNIQUE(leerplan_id, oefenreeks_id); ALTER TABLE leerplan_oefenreeks ADD CONSTRAINT un_leerp_oefenr_plaats UNIQUE(leerplan_id, plaats); When I go and check only 3 constraints exist. fk_leerp_oefenr_leerplan disappears. I don't understand why this happens.

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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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  • 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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  • 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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  • 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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  • Unique visitor counting in ASP.NET MVC

    - by Max
    I'd like to do visitor tracking similar to how stackoverflow does it.. By reading through numerous posts, I've figured out some details already: Count only 1 IP hit per 15 minutes (if anonymous) Count only 1 unique user-Login (per day?) Now that leaves the question of the real implementation.. Should I log the two factors live into a table (and increase count) | IP | timestamp | pageurl | Or do the counting AFTERWARDS (e.g. using IIS log files - which don't include the user, right? I know there're some similar posts outside, but NONE really has a great solution in my opinion yet..

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  • manipulating 15+ million records in mysql with php?

    - by Nithish
    Hey, I got a user table containing 15+ million records and while doing the registration function i wish to check whether the username already exist. I did indexing for username column and when i run the query "select count(uid) from users where username='webdev'" ,. hmmm, its keep on loading blank screen finally hanged up. I'm doing this in my localhost with php 5 & mysql 5. So suggest me some technique to handle this situation. Is that mongodb is good alternative for handling this process in our local machine? Thanks, Nithish.

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  • merging two tables, while applying aggregates on the duplicates (max,min and sum)

    - by cloudraven
    I have a table (let's call it log) with a few millions of records. Among the fields I have Id, Count, FirstHit, LastHit. Id - The record id Count - number of times this Id has been reported FirstHit - earliest timestamp with which this Id was reported LastHit - latest timestamp with which this Id was reported This table only has one record for any given Id Everyday I get into another table (let's call it feed) with around half a million records with these fields among many others: Id Timestamp - Entry date and time. This table can have many records for the same id What I want to do is to update log in the following way. Count - log count value, plus the count() of records for that id found in feed FirstHit - the earliest of the current value in log or the minimum value in feed for that id LastHit - the latest of the current value in log or the maximum value in feed for that id. It should be noticed that many of the ids in feed are already in log. The simple thing that worked is to create a temporary table and insert into it the union of both as in Select Id, Min(Timestamp) As FirstHit, MAX(Timestamp) as LastHit, Count(*) as Count FROM feed GROUP BY Id UNION ALL Select Id, FirstHit,LastHit,Count FROM log; From that temporary table I do a select that aggregates Min(firsthit), max(lasthit) and sum(Count) Select Id, Min(FirstHit),Max(LastHit),Sum(Count) FROM @temp GROUP BY Id; and that gives me the end result. I could then delete everything from log and replace it with everything with temp, or craft an update for the common records and insert the new ones. However, I think both are highly inefficient. Is there a more efficient way of doing this. Perhaps doing the update in place in the log table?

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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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  • 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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  • Any way to make this PostgreSQL count query any faster?

    - by Ben Dauphinee
    I'm running a case-insensitive search on a table with 7.2 million rows, and I was wondering if there was any way to make this query any faster? Currently, it takes approx 11.6 seconds to execute, with just one search parameter, and I'm worried that as soon as I add more than one, this query will become massively slow. SELECT count(*) FROM "exif_parse" WHERE (description ~* 'canon')

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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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  • retrieving the record which has only one value

    - by ashwani66476
    Hello All, Please suggest me a query, which retrieves only those record which has the single row in table. For Example table1. name age aaa 20 bbb 10 ccc 20 ddd 30 If I run "select distinct age from table1. result will be age 20 10 30 But I need a query, which give the result like name age bbb 10 ddd 30 Thanks....

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  • what is the out put?

    - by user329820
    Hi this is my code but when I run it in mysql it will show an error because of datatype but my friend checked it with sql server and it doesn't show error and also insert the value: 32769 .which of them is correct? CREATE TABLE T1 (A INTEGER NOT NULL); INSERT T1 VALUES (32768.5);

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  • References/walkthroughs for maintaining database schemas with Visual Studio 2010?

    - by user206356
    I have Visual Studio 2010 Beta 2 and SQL Server 2008 installed. I'm working with a populated database and want to modify various column types. SQL Server Management Studio requires me to drop tables to do this, and get pretty finicky given my moderate level of knowledge of SQL Server. However, I heard the new database project type supports changing the database schema to the desired format and it will handle creating and running all the scripts to implement the changes. I've created a VS2010 database project using the existing database as the source, but so far haven't had much luck figuring out the appropriate method to make the changes without getting an error. As a result, I'm looking for any reference info I can find on using VS2010's capabilities in this area. Any suggestions?

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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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