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  • Which index is used in select and why?

    - by Lukasz Lysik
    I have the table with zip codes with following columns: id - PRIMARY KEY code - NONCLUSTERED INDEX city When I execute query SELECT TOP 10 * FROM ZIPCodes I get the results sorted by id column. But when I change the query to: SELECT TOP 10 id FROM ZIPCodes I get the results sorted by code column. Again, when I change the query to: SELECT TOP 10 code FROM ZIPCodes I get the results sorted by code column again. And finally when I change to: SELECT TOP 10 id,code FROM ZIPCodes I get the results sorted by id column. My question is in the title of the question. I know which indexes are used in the queries, but my question is, why those indexes are used? I the second query (SELECT TOP 10 id FROM ZIPCodes) wouldn't it be faster if the clusteder index was used? How the query engine chooses which index to use?

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  • Index for wildcard match of end of string

    - by Anders Abel
    I have a table of phone numbers, storing the phone number as varchar(20). I have a requirement to implement searching of both entire numbers, but also on only the last part of the number, so a typical query will be: SELECT * FROM PhoneNumbers WHERE Number LIKE '%1234' How can I put an index on the Number column to make those searchs efficient? Is there a way to create an index that sorts the records on the reversed string? Another option might be to reverse the numbers before storing them, which will give queries like: SELECT * FROM PhoneNumbers WHERE ReverseNumber LIKE '4321%' However that will require all users of the database to always reverse the string. It might be solved by storing both the normal and reversed number and having the reversed number being updated by a trigger on insert/update. But that kind of solution is not very elegant. Any other suggestions?

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  • How do I select a random record efficiently in MySQL?

    - by user198729
    mysql> EXPLAIN SELECT * FROM urls ORDER BY RAND() LIMIT 1; +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ | 1 | SIMPLE | urls | ALL | NULL | NULL | NULL | NULL | 62228 | Using temporary; Using filesort | +----+-------------+-------+------+---------------+------+---------+------+-------+---------------------------------+ The above doesn't qualify as efficient,how should I do it properly?

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  • How to analyse Wikipedia article's data base with R?

    - by Tal Galili
    Hi all, This is a "big" question, that I don't know how to start, so I hope some of you can give me a direction. And if this is not a "good" question, I will close the thread with an apology. I wish to go through the database of Wikipedia (let's say the English one), and do statistics. For example, I am interested in how many active editors (which should be defined) Wikipedia had at each point of time (let's say in the last 2 years). I don't know how to build such a database, how to access it, how to know which types of data it has and so on. So my questions are: What tools do I need for this (besides basic R) ? MySQL on my computer? RODBC database connection? How do you start planning for such a project?

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  • Only show certain items in a mysql database using php and time()

    - by Jon
    Is there a way to only show the items that are older than a certain date in a php mysql array? I'm using this query method and sorting by lastpost_cl: $query="SELECT * FROM properties ORDER BY lastpost_cl"; $result=mysql_query($query); $num = mysql_num_rows ($result); mysql_close(); and I was thinking the way of checking the time would be: if (time() <= strtotime($lastpost_cl)) { } How can I combine the two and only show lastpost_cl that are older that the current time?

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  • how do I integrate the aspnet_users table (asp.net membership) into my existing database

    - by ooo
    i have a database that already has a users table COLUMNS: userID - int loginName - string First - string Last - string i just installed the asp.net membership table. Right now all of my tables are joined into my users table foreign keyed into the "userId" field How do i integrate asp.net_users table into my schema? here are the ideas i thought of: Add a membership_id field to my users table and on new inserts, include that new field in my users table. This seems like the cleanest way as i dont need to break any existing relationships. break all existing relationship and move all of the fields in my user table into the asp.net_users table. This seems like a pain but ultimately will lead to the most simple, normalized solution any thoughts?

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  • Extract time part from TimeStamp column in ORACLE

    - by RRUZ
    Actually i' am using MyTimeStampField-TRUNC(MyTimeStampField) to extract the time part from an timestamp column in Oracle. SELECT CURRENT_TIMESTAMP-TRUNC(CURRENT_TIMESTAMP) FROM DUAL this return +00 13:12:07.100729 this work ok for me, to extract the time part from an timestamp field, but i' m wondering if exist a better way (may be using an built-in function of ORACLE) to do this? Thanks.

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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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  • MYSQL to UPDATE table if row with 2 specific columns exist or INSERT new row if it does not exist

    - by user2509541
    I have a MYSQL table that looks as follows: id id_jugador id_partido team1 team2 1 2 1 5 2 2 2 2 1 1 3 1 2 0 0 I need to create a query to either INSERT new rows in the table or UPDATE the table. The condition is based on id_jugador and id_partido, meaning that if I wanted to insert id_jugador = 2 and id_partido = 1, then it should just UPDATE the existing row with the new team1 and team2 values I am sending. And dont duplicate the row. However, if I have an entry id_jugador=2 and id_partido=3, since this combination does not exist yet, it should add the new row. I read about the REPLACE INTO but it seems to be unable to check combination of UNIQUE KEYS.

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  • Date/time query from Access table ( last month)

    - by chupeman
    Hello, I am using the query builder from Visual Studio 2008 to extract data from an Access mdb ( 2003), but I can't make it to work with a datetime field. When I run it with a third party query app I have works fine, but when I try to implement it into visual studio I can't do it. What is the correct way to extract last month data? This is what I have: SELECT [Datos].[ID], [Datos].[E-mail Address], [Datos].[ZIP/Postal Code], [Datos].[Store], [Datos].[date], [Datos].[gender], [Datos].[age] FROM [Datos] WHERE ([Datos].[date] =<|Last month|>) Any help is appreciated. Thank you

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  • Joining 3 tables - doing joins how to

    - by Kieran
    This is my current query - its not getting the required result. I want it do display all of the "resources" even if they dont have a connection. SELECT * FROM (`user_permissions`) JOIN `user_groups` ON `user_groups`.`id` = `user_permissions`.`role` JOIN `user_resources` ON `user_resources`.`id` = `user_permissions`.`resource` WHERE `role` = '4' When I try left join or right join it still returns the same result. The result I get is: id | role | resource | name 5 | 4 | 2 | Changelog I want id | role | resource | name 5 | 4 | 2 | Changelog null | null | null | Resource2 null | null | null | Resource3 Is this possible?

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  • Getting "too many rows" error inside a "for" cursor loop

    - by Will
    I have a trigger that contains two cursors loops, one nested inside the other like this: FOR outer_rec IN outer_cursor LOOP FOR inner_rec IN inner_cursor LOOP -- Do some calculations END LOOP; END LOOP; Somewhere in this it is throwing the following error: ORA-01422: exact fetch returns more than requested number of rows I've been trying to determine where it's coming from for an hour or so.. but should this error never happen? Also.. I am assuming the inner loop automatically closes and opens itself again every time the outer loop goes the next record, i hope this is correct.

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  • Violation of primary key constraint, multiple users

    - by MC.
    Lets say UserA and UserB both have an application open and are working with the same type of data. UserA inserts a record into the table with value 10 (PrimaryKey='A'), UserB does not currently see the value UserA entered and attempts to insert a new value of 20 (PrimaryKey='A'). What I wanted in this situation was a DBConcurrencyException, but instead what I have is a primary key violation. I understand why, but I have no idea how to resolve this. What is a good practice to deal with such a circumstance? I do not want to merge before updating the database because I want an error to inform the user that multiple users updated this data.

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  • Select fields containing at least one non-space alphanumeric character

    - by zzapper
    (Sorry I know this is an old chestnut; I have found similar answers here but not an exact answer) These are frequent hand written queries from a console so I is what I am looking for is the easiest thing to type SELECT * FROM tbl_loyalty_card WHERE CUSTOMER_ID REGEXP "[0-9A-Z]"; or SELECT * FROM tbl_loyalty_card WHERE LENGTH(CUSTOMER_ID) >0; -- could match spaces Do you have anything quicker to type even if it's QAD?

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  • Count total number of callers?

    - by Kristopher Ives
    I'm currently doing this query to find the guy who makes the most calls: SELECT `commenter_name`, COUNT(*) AS `calls` FROM `comments` GROUP BY `commenter_name` ORDER BY `calls` LIMIT 1 What I want now is to be able to find out how many total unique callers. I tried using DISTINCT but I didn't get anywhere.

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  • making an SQL date column visible to a Drupal view

    - by Donal
    I'm trying to make a table visible to Views. One of the columns has type date (as opposed to a Unix timestamp). The example I initially tried to copy from is in modules/comment.views.inc in the Views module: // timestamp (when comment was posted) $data['comments']['timestamp'] = array( 'title' => t('Post date'), 'help' => t('Date and time of when the comment was posted.'), 'field' => array( 'handler' => 'views_handler_field_date', 'click sortable' => TRUE, ), 'sort' => array( 'handler' => 'views_handler_sort_date', ), 'filter' => array( 'handler' => 'views_handler_filter_date', ), ); This makes the dates, which are all in the past year or so, show up as "1 Jan 1970 00:33", so evidently a value of '2010-05-12', for example, is being interpreted as 2010 seconds past 1 Jan 1970 00:00. Can anyone point me to a correct way of exporting date columns? EDIT: I'm following up on some clues found at http://drupal.org/node/476774 .

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  • Embedded Java Databases for Large Data Sets

    - by ExAmerican
    I would like to port a PHP/MySQL-based client/server application to be a standalone desktop application written in Java. The database has grown to be fairly large, with several tables with hundreds of thousands of rows. I expect these could grow to over a million entries for certain tables. What embedded database would best handle this? HSQLDB and Sqlite seem to be the obvious choices, though I'm guessing there are others out there as well. My main priorities are the ability to perform queries on large amounts of data efficiently (this thread seems to confirm Sqlite can handle this) and the ease with which I can import old data from MySQL (I remember HSQLDB being kind of a pain for that). Note: I am aware that similar questions comparing embedded databases have been posted before (for example here and here) but as my priorities differ somewhat from most applications considering the large data migration I thought it justified a new question.

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  • move data from one table to another, postgresql edition

    - by IggShaman
    Hi All, I'd like to move some data from one table to another (with a possibly different schema). Straightforward solution that comes into mind is - start a transaction with serializable isolation level; INSERT INTO dest_table SELECT data FROM orig_table,other-tables WHERE <condition>; DELETE FROM orig_table USING other-tables WHERE <condition>; COMMIT; Now what if the amount of data is rather big, and the <condition> is expensive to compute? In PostgreSQL, a RULE or a stored procedure can be used to delete data on the fly, evaluating condition only once. Which solution is better? Are there other options?

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  • how to do multi insert and obtain ids

    - by liysd
    hi, I want to insert some data into a table (id PK autoincrement, val) with use multi insert INSERT INTO tab (val) VALUES (1), (2), (3) Is it possible to obtain a table of last inserted ids? I'm asking becouse I'm not sure if all will in this form: (n, n+1, n+2). I use mysql inodb.

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  • Session or Query

    - by Khou
    Should I store the user's ID, name & email address in a session variable or should I query for the user's user's ID, name & email address everytime i need to use it?

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