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  • How extension methods work in background ?

    - by Freshblood
    I am just cuirous about behind of extension method mechanism.Some questions and answer appear in my mind. MyClass.OrderBy(x=>x.a).OrderBy(x=>x.b); I was guessing that mechanism was first orderby method works and order them by a member then returns sorted items in IEnumarable interface then next Orderby method of IEnumarable Order them for b paramater.But i am wrong when i look at this linq query. MyClass.Orderby(x=>x.a).ThenOrderBy(x=>x.b); this is slightly different and tells me that i am wrong.Because this is not ordering by a then b and not possible to have such result if i was right.This get me confuse enough... Similiar structure is possible to write withot extension methods as first query but second is not possible.This prove i am wrong . Can u explain it ?

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  • How to get count of another table in a left join

    - by Sinan
    I have multiple tables post id Name 1 post-name1 2 post-name2 user id username 1 user1 2 user2 post_user post_id user_id 1 1 2 1 post_comments post_id comment_id 1 1 1 2 1 3 I am using a query like this: SELECT post.id, post.title, user.id AS uid, username FROM `post` LEFT JOIN post_user ON post.id = post_user.post_id LEFT JOIN user ON user.id = post_user.user_id ORDER BY post_date DESC It works as intended. However I would like the get the number of comments for each post too. So how can i modify the this query so I can get the count of comments. Any ideas?

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  • Speed up multiple JDBC SQL querys?

    - by paddydub
    I'm working on a shortest path a* algorithm in java with a mysql db. I'm executing the following SQL Query approx 300 times in the program to find route connections from a database of 10,000 bus connections. It takes approx 6-7 seconds to execute the query 300 times. Any suggestions on how I can speed this up or any ideas on a different method i can use ? Thanks ResultSet rs = stmt.executeQuery("select * from connections" + " where Connections.From_Station_stopID ="+StopID+";"); while (rs.next()) { int id = rs.getInt("To_Station_id"); String routeID = rs.getString("To_Station_routeID"); Double lat = rs.getDouble("To_Station_lat"); Double lng = rs.getDouble("To_Station_lng"); int time = rs.getInt("Time"); }

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  • Using SQL to get the Last Reply on a Post

    - by Anraiki
    I am trying to replicate a forum function by getting the last reply of a post. For clarity, see PHPBB: there are four columns, and the last column is what I like to replicate. I have my tables created as such: discussion_id (primary key) user_id parent_id comment status pubdate I was thinking of creating a Link Table that would update for each time the post is replied to. The link table would be as follow: discussion_id (primary key) last_user_id last_user_update However, I am hoping that theres a advance query to achieve this method. That is, grabbing each Parent Discussion, and finding the last reply in each of those Parent Discussions. Am I right that there is such a query?

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  • Which field is explain telling me to index?

    - by shady
    I don't understand what this explain statement is saying. Which field needs an index?. The first line to me is confusing because ref is null. Here's the query I'm using: SELECT pp.property_id AS 'good_prop_id', pr.site_number AS 'pr.site_number', CONCAT(pr.site_street_name, ' ', pr.site_street_type) AS 'pr.partial_addr', pr.county FROM realval_newdb.preforeclosures AS pr INNER JOIN realval_newdb.properties_preforeclosures AS pp USE INDEX (mee_id) ON (pr.mee_id = pp.mee_id) INNER JOIN listings_copy AS lc ON (pr.site_number = lc.site_number) AND (lc.site_street_name = CONCAT(pr.site_street_name, ' ', pr.site_street_type)) WHERE lc.site_county = pr.county LIMIT 1; Can anyone help me optimize this query?

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  • User has many computers, computers have many attributes in different tables, best way to JOIN?

    - by krismeld
    I have a table for users: USERS: ID | NAME | ---------------- 1 | JOHN | 2 | STEVE | a table for computers: COMPUTERS: ID | USER_ID | ------------------ 13 | 1 | 14 | 1 | a table for processors: PROCESSORS: ID | NAME | --------------------------- 27 | PROCESSOR TYPE 1 | 28 | PROCESSOR TYPE 2 | and a table for harddrives: HARDDRIVES: ID | NAME | ---------------------------| 35 | HARDDRIVE TYPE 25 | 36 | HARDDRIVE TYPE 90 | Each computer can have many attributes from the different attributes tables (processors, harddrives etc), so I have intersection tables like this, to link the attributes to the computers: COMPUTER_PROCESSORS: C_ID | P_ID | --------------| 13 | 27 | 13 | 28 | 14 | 27 | COMPUTER_HARDDRIVES: C_ID | H_ID | --------------| 13 | 35 | So user JOHN, with id 1 owns computer 13 and 14. Computer 13 has processor 27 and 28, and computer 13 has harddrive 35. Computer 14 has processor 27 and no harddrive. Given a user's id, I would like to retrieve a list of that user's computers with each computers attributes. I have figured out a query that gives me a somewhat of a result: SELECT computers.id, processors.id AS p_id, processors.name AS p_name, harddrives.id AS h_id, harddrives.name AS h_name, FROM computers JOIN computer_processors ON (computer_processors.c_id = computers.id) JOIN processors ON (processors.id = computer_processors.p_id) JOIN computer_harddrives ON (computer_harddrives.c_id = computers.id) JOIN harddrives ON (harddrives.id = computer_harddrives.h_id) WHERE computers.user_id = 1 Result: ID | P_ID | P_NAME | H_ID | H_NAME | ----------------------------------------------------------- 13 | 27 | PROCESSOR TYPE 1 | 35 | HARDDRIVE TYPE 25 | 13 | 28 | PROCESSOR TYPE 2 | 35 | HARDDRIVE TYPE 25 | But this has several problems... Computer 14 doesnt show up, because it has no harddrive. Can I somehow make an OUTER JOIN to make sure that all computers show up, even if there a some attributes they don't have? Computer 13 shows up twice, with the same harddrive listet for both. When more attributes are added to a computer (like 3 blocks of ram), the number of rows returned for that computer gets pretty big, and it makes it had to sort the result out in application code. Can I somehow make a query, that groups the two returned rows together? Or a query that returns NULL in the h_name column in the second row, so that all values returned are unique? EDIT: What I would like to return is something like this: ID | P_ID | P_NAME | H_ID | H_NAME | ----------------------------------------------------------- 13 | 27 | PROCESSOR TYPE 1 | 35 | HARDDRIVE TYPE 25 | 13 | 28 | PROCESSOR TYPE 2 | 35 | NULL | 14 | 27 | PROCESSOR TYPE 1 | NULL | NULL | Or whatever result that make it easy to turn it into an array like this [13] => [P_NAME] => [0] => PROCESSOR TYPE 1 [1] => PROCESSOR TYPE 2 [H_NAME] => [0] => HARDDRIVE TYPE 25 [14] => [P_NAME] => [0] => PROCESSOR TYPE 1

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  • How to join table to itself and select max values in SQL

    - by Jakub Konop
    I have a contracts table: contractId date price partId 1 20120121 10 1 2 20110130 9 1 3 20130101 15 2 4 20110101 20 2 The contract with greatest date being the active contract (don't blame me, I blame infor for creating xpps) I need to create query to see only active contracts (one contract per part, the contract with highest date). So the result of the query should be like this: contractId date price partId 1 20120121 10 1 3 20130101 15 2 I am out of ideas here, I tried self joining the table, I tried aggregation functions, but I can't figure it out. If anyone would have any idea, please share them with me..

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  • Table alias -- Unkown column in field list

    - by Jason
    Hi all, I have a sql query which is executing a LEFT JOIN on 2 tables in which some of the columns are ambiguous. I can prefix the joined tables but when I try to prefix one of the columns from the table in the FROM clause, it tells me Unknown column. I even tried giving that table an alias like so ...From points AS p and using "p" to prefix the tables but that didn't work either. Can someone tell me what I'm doing wrong. Here is my query: SELECT point_title, point_url, address, city, state, zip_code, phone, `points`.`lat`, `points`.`longi`, featured, kmlno, image_url, category.title, category_id, point_id, lat, longi, reviews.star_points, reviews.review_id, count(reviews.point_id) as totals FROM (SELECT *, ( 3959 * acos( cos( radians('37.7717185') ) * cos( radians( lat ) ) * cos( radians( longi ) - radians('-122.4438929') ) + sin( radians('37.7717185') ) * sin( radians( lat ) ) ) ) AS distance FROM points HAVING distance < '25') as distResults LEFT JOIN category USING ( category_id ) LEFT JOIN reviews USING ( point_id ) WHERE (point_title LIKE '%Playgrounds%' OR category.title LIKE '%Playgrounds%') GROUP BY point_id ORDER BY totals DESC, distance LIMIT 0 , 10

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  • PHP Export Date range

    - by menormedia
    I have a working database export to xls but I need it to export a particular date range based on the 'closed' date. (See code below). For example, I'd like it to export all 'closed' dates for last month and/or this month (Range: Sept 1, 2012 to Sept 30, 2012 or Oct 1, 2012 to Oct 31, 2012) <?PHP //EDIT YOUR MySQL Connection Info: $DB_Server = "localhost"; //your MySQL Server $DB_Username = "root"; //your MySQL User Name $DB_Password = ""; //your MySQL Password $DB_DBName = "ost_helpdesk"; //your MySQL Database Name $DB_TBLName = "ost_ticket"; //your MySQL Table Name //$DB_TBLName, $DB_DBName, may also be commented out & passed to the browser //as parameters in a query string, so that this code may be easily reused for //any MySQL table or any MySQL database on your server //DEFINE SQL QUERY: //edit this to suit your needs $sql = "Select ticketID, name, company, subject, closed from $DB_TBLName ORDER BY closed DESC"; //Optional: print out title to top of Excel or Word file with Timestamp //for when file was generated: //set $Use_Titel = 1 to generate title, 0 not to use title $Use_Title = 1; //define date for title: EDIT this to create the time-format you need $now_date = DATE('m-d-Y'); //define title for .doc or .xls file: EDIT this if you want $title = "MDT Database Dump For Table $DB_TBLName from Database $DB_DBName on $now_date"; /* Leave the connection info below as it is: just edit the above. (Editing of code past this point recommended only for advanced users.) */ //create MySQL connection $Connect = @MYSQL_CONNECT($DB_Server, $DB_Username, $DB_Password) or DIE("Couldn't connect to MySQL:<br>" . MYSQL_ERROR() . "<br>" . MYSQL_ERRNO()); //select database $Db = @MYSQL_SELECT_DB($DB_DBName, $Connect) or DIE("Couldn't select database:<br>" . MYSQL_ERROR(). "<br>" . MYSQL_ERRNO()); //execute query $result = @MYSQL_QUERY($sql,$Connect) or DIE("Couldn't execute query:<br>" . MYSQL_ERROR(). "<br>" . MYSQL_ERRNO()); //if this parameter is included ($w=1), file returned will be in word format ('.doc') //if parameter is not included, file returned will be in excel format ('.xls') IF (ISSET($w) && ($w==1)) { $file_type = "msword"; $file_ending = "doc"; }ELSE { $file_type = "vnd.ms-excel"; $file_ending = "xls"; } //header info for browser: determines file type ('.doc' or '.xls') HEADER("Content-Type: application/$file_type"); HEADER("Content-Disposition: attachment; filename=MDT_DB_$now_date.$file_ending"); HEADER("Pragma: no-cache"); HEADER("Expires: 0"); /* Start of Formatting for Word or Excel */ IF (ISSET($w) && ($w==1)) //check for $w again { /* FORMATTING FOR WORD DOCUMENTS ('.doc') */ //create title with timestamp: IF ($Use_Title == 1) { ECHO("$title\n\n"); } //define separator (defines columns in excel & tabs in word) $sep = "\n"; //new line character WHILE($row = MYSQL_FETCH_ROW($result)) { //set_time_limit(60); // HaRa $schema_insert = ""; FOR($j=0; $j<mysql_num_fields($result);$j++) { //define field names $field_name = MYSQL_FIELD_NAME($result,$j); //will show name of fields $schema_insert .= "$field_name:\t"; IF(!ISSET($row[$j])) { $schema_insert .= "NULL".$sep; } ELSEIF ($row[$j] != "") { $schema_insert .= "$row[$j]".$sep; } ELSE { $schema_insert .= "".$sep; } } $schema_insert = STR_REPLACE($sep."$", "", $schema_insert); $schema_insert .= "\t"; PRINT(TRIM($schema_insert)); //end of each mysql row //creates line to separate data from each MySQL table row PRINT "\n----------------------------------------------------\n"; } }ELSE{ /* FORMATTING FOR EXCEL DOCUMENTS ('.xls') */ //create title with timestamp: IF ($Use_Title == 1) { ECHO("$title\n"); } //define separator (defines columns in excel & tabs in word) $sep = "\t"; //tabbed character //start of printing column names as names of MySQL fields FOR ($i = 0; $i < MYSQL_NUM_FIELDS($result); $i++) { ECHO MYSQL_FIELD_NAME($result,$i) . "\t"; } PRINT("\n"); //end of printing column names //start while loop to get data WHILE($row = MYSQL_FETCH_ROW($result)) { //set_time_limit(60); // HaRa $schema_insert = ""; FOR($j=0; $j<mysql_num_fields($result);$j++) { IF(!ISSET($row[$j])) $schema_insert .= "NULL".$sep; ELSEIF ($row[$j] != "") $schema_insert .= "$row[$j]".$sep; ELSE $schema_insert .= "".$sep; } $schema_insert = STR_REPLACE($sep."$", "", $schema_insert); //this corrects output in excel when table fields contain \n or \r //these two characters are now replaced with a space $schema_insert = PREG_REPLACE("/\r\n|\n\r|\n|\r/", " ", $schema_insert); $schema_insert .= "\t"; PRINT(TRIM($schema_insert)); PRINT "\n"; } } ?>

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  • MySQL select two tables at the same time...

    - by Jerry
    Hi all I have two tables and want to make a query. I tried to get team AA and team BB's image base on table A. I used: SELECT tableA.team1, tableA.team2, tableB.team, tableB.image, FROM tableA LEFT JOIN tableB ON tableA.team1=tableB.team The result only display imageA on the column. Are there any ways to select imageA and image B without using the second query? I appreciate any helps! Thanks a lot! My table structure are: table A team1 team2 ------------ AA BB table B team image ------------- AA imagaA BB imageB

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  • How to order by results from 2 seperate tables in PHP and MySQL.

    - by Vafello
    I am trying to output results of 2 sql queries to one JSON file. The problem is that I would like to order them ascending by distance which is the result of equation that takes homelat and homelon from the users table and lat, lng from locations table.(basically it takes lattitude and longitude of one point and another and computes the distance between these points). Is it possible to take some parameters from both select queries, compute it and output the result in ascending order? $wynik = mysql_query("SELECT homelat, homelon FROM users WHERE guid='2'") or die(mysql_error()); ; $query = "SELECT * FROM locations WHERE timestamp"; $result = map_query($query); $points = array(); while ($aaa = mysql_fetch_assoc($wynik)) { while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) { array_push($points, array('name'=>$row['name'], 'lat'=>$row['lat'], 'lng'=>$row['lng'], 'description'=>$row['description'], 'eventType'=>$row['eventType'], 'date'=>$row['date'], 'isotime'=>date('c', ($row['timestamp'])), 'homelat'=>$aaa['homelat'], 'homelon'=>$aaa['homelon'])); } echo json_encode(array("Locations"=>$points));

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  • Accessing global variables within functions in PHP

    - by st3
    There are multiple times in one page where I need to connect and subsequently query a MySQL database, yet my code won't let me. I think it might be something to do with how my files are nested but it makes no sense. I am opening the SQL connection in the header file. The top of the offending page looks like the following: <?php $page_title = 'Dashboard'; include('templates/header.inc'); // includes a 'require_once('mysqli_connect.php') and a small query to the database; require_once('includes/functions.php'); require_once('includes/dashboard_sql.php'); // Contains functions which connect to database (which are failing.) ?> I get the PHP error Notice: Undefined variable: dbc in /Library/WebServer/Documents/pediatory_site/includes/dashboard_sql.php Where $dbc is the database connection defined in mysqli_connect.php. If anyone could help me out that would be great.

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  • MySQL, return only rows where there are duplicates among two columns.

    - by Richard Waite
    I have a table in MySQL of contact information ; first name, last name, address, etc. I would like to run a query on this table that will return only rows with first and last name combinations which appear in the table more than once. I do not want to group the "duplicates" (which may only be duplicates of the first and last name, but not other information like address or birthdate) - I want to return all the "duplicate" rows so I can look over the results and determine if they are dupes or not. This seemed like it would be a simple thing to do, but it has not been. Every solution I can find either groups the dupes and gives me a count only (which is not useful for what I need to do with the results) or doesn't work at all. Is this kind of logic even possible in a query ? Should I try and do this in Python or something?

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  • Display rows from MySQL where a datetime is within the next hour

    - by alex
    I always have trouble with complicated SQL queries. This is what I have $query = ' SELECT id, name, info, date_time FROM acms_events WHERE date_time = DATE_SUB(NOW(), INTERVAL 1 HOUR) AND active = 1 ORDER BY date_time ASC LIMIT 6 '; I want to get up to 6 rows that are upcoming within the hour. Is my query wrong? It does not seem to get events that are upcoming within the next hour when I test it. What is the correct syntax for this? Thanks

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  • How to prompt user input parameters for SQL Queries in Access 2010

    - by user1848907
    SELECT Transactions.TransactionNumber FROM Transactions WHERE (((Transactions.Date)>=#11/23/12#)) AND (((Transactions.Date)<=#11/23/12#)); The above code returns all the transaction that happened between the specified dates. But I want those dates to be defined by the user every time the query is executed. I tried using the [] operators to have the user define the criteria in the WHERE, something like this: WHERE (((Transactions.Date)>=[Input a Date])) AND (((Transactions.Date)<=[Input a Date])); But microsoft Access throws a Syntax error message. The same happens when I include the # (date operators) like this WHERE (((Transactions.Date)>=#[Input a Date]#)) AND (((Transactions.Date)<=#[Input a Date]#)); Is there anopther way to manage dates that I'm not aware of or is asking a user for dates in a query out of the question

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  • Techniques for querying a set of object in-memory in a Java application

    - by Edd Grant
    Hi All, We have a system which performs a 'coarse search' by invoking an interface on another system which returns a set of Java objects. Once we have received the search results I need to be able to further filter the resulting Java objects based on certain criteria describing the state of the attributes (e.g. from the initial objects return all objects where x.y z && a.b == c). The criteria used to filter the set of objects each time is partially user configurable, by this I mean that users will be able to select the values and ranges to match on but the attributes they can pick from will be a fixed set. The data sets are likely to contain <= 10,000 objects for each search. The search will be executed manually by the application user base probably no more than 2000 times a day (approx). It's probably worth mentioning that all the objects in the result set are known domain object classes which have Hibernate and JPA annotations describing their structure and relationship. Off the top of my head I can think of 3 ways of doing this: For each search persist the initial result set objects in our database, then use Hibernate to re-query them using the finer grained criteria. Use an in-memory Database (such as hsqldb?) to query and refine the initial result set. Write some custom code which iterates the initial result set and pulls out the desired records. Option 1 seems to involve a lot of toing and froing across a network to a physical Database (Oracle 10g) which might result in a lot of network and disk activity. It would also require the results from each search to be isolated from other result sets to ensure that different searches don't interfere with each other. Option 2 seems like a good idea in principle as it would allow me to do the finer query in memory and would not require the persistence of result data which would only be discarded after the search was complete. Gut feeling is that this could be pretty performant too but might result in larger memory overheads (which is fine as we can be pretty flexible on the amount of memory our JVM gets). Option 3 could be very performant but is something I would like to avoid as any code we write would require such careful testing that the time taken to acheive something flexible and robust enough would probably be prohibitive. I don't have time to prototype all 3 ideas so I am looking for comments people may have on the 3 options above, plus any further ideas I have not considered, to help me decide which idea might be most suitable. I'm currently leaning toward option 2 (in memory database) so would be keen to hear from people with experience of querying POJOs in memory too. Hopefully I have described the situation in enough detail but don't hesitate to ask if any further information is required to better understand the scenario. Cheers, Edd

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  • SQL Server 2008 + expensive union all

    - by Tim Mahy
    Hi al, we have 5 tables over which we should query with user search input throughout a stored procedure. We do a union all of the similar data inside a view. Because of this the view can not be materialized. We are not able to change these 5 tables drastically (like creating a 6th table that contains the similar data of the 5 tables and reference that new one from the 5 tables). The query is rather expensive / slow what are our other options? It's allowed to think outside the box. Unfortunately I cannot give more information like the table/view/SP definition because of customer confidentiality... greetings, Tim

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  • Getting unique items from NSMutableArray

    - by Gidogeek
    Hi Guys, I have a question about Objective-C today involving NSMutableArray. Coming from a .net/c# background I'm having some trouble working with these things. Let's say I have an object called "Song" My song has 3 properties: Title Artist Genre I have a NSMutableArray or NSArray wich holds all my Song objects. How would I go about trying to 'query' my array to get a new array with only (Unique) Artists or Genre's. Where as in .net you would write a simple LINQ query with a DISTINCT clause, how would one solve this in Objective-C ? I'm guessing with predicates but am struggling to find a solution. Thanks in advance.

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  • How to access java collection, just like the table in the database, having indexes and LINQ-like que

    - by Shaman
    This task occurs from time to time in my projects. I need to handle a collection of some complex elements, having different attributes, such as login, password_hash, role, etc. And, I need to be able to query that collection, just like I query a table in the database, having only partial data. For example: get all users, with role "user". Or check, if there's a user with login "root" and role "superuser". Removing items, based on same data is also needed. The first attempt I've tried is to use Google collections, Apache collections, and lambdaj. All of them have very similar preicate mechanism, but with a great disadvantage: it is based on iteration, one by one, over the collection of items, which is not good, for often used collections, containing big amounts of data. Could you please suggest me some solution? Thanks.

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  • Should i really use integer primary IDs [sql]

    - by arthurprs
    For example, i always generate an auto-increment field for the users table, but i also specifies an UNIQUE index on their usernames. There is situations that i first need to get the userId for a given username and then execute the desired query. Or use a JOIN in the desired query. It's 2 trips to the database or a JOIN vs. a varchar index The above is just an example There is a real performance benefit on INT over small VARCHAR indexes? Thanks in advance!

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  • Select all rows where there is not a specific value in a different table

    - by JMC Creative
    This is a wordpress installation, but I think the question is more of a general sql question. First off, my sql skills are not great (I don't even know if I'm following the correct format for illustrating the db). I've got two tables: wp_posts : ID (pk) | post_name | ... ---------------------------- 45 | "Hello" 91 | "Funny" 16 | "Wheat" wp_postmeta : post_id (fk) | meta_key | meta_value | ... ------------------------------------------------ 45 | "_edit_lock" | 5789789834 45 | "fizzbizz" | "foobar" 91 | "_something" | "teve" 16 | "_edit_lock" | 8798756 I would to select all rows in wp_posts where there is NO corresponding row in wp_postmeta where meta_key = "fizzbizz" I originally had this query, but someone pointed out that it would not retrive ID = '16' in the above case. How would I correctly write the query? $pageposts = $wpdb->get_results(" SELECT * FROM wp_posts p JOIN wp_postmeta m ON p.ID = m.post_id WHERE m.meta_key <> 'fizzbizz' ORDER BY p.post_date DESC; ");

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  • Microsoft Access - Enter Parameter Value why?

    - by Jane Doe
    I am encountering a problem for my database. Here is the relationships of the database And tried to do the query for how many transactions have movie "Harry_Potter"? so I used SQL query: SELECT COUNT(td.movie) AS number_of_occurrence, td.transaction_number FROM TransactionDetails td, MovieDetails md WHERE md.movie = Harry_Potter But it asks for Harry_Potter enter parameter value why? The relevant SQL statements are CREATE TABLE TransactionDetails ( transaction_number INTEGER PRIMARY KEY, movie VARCHAR(30) NOT NULL, date_of_transaction DATE NOT NULL, member_number INTEGER NOT NULL ) CREATE TABLE MovieDetails ( movie VARCHAR(30) PRIMARY KEY, movie_type VARCHAR(3) NOT NULL, movie_genre VARCHAR(10) NOT NULL ) ALTER TABLE TransactionDetails ADD CONSTRAINT member_number_fk FOREIGN KEY (member_number) REFERENCES LimelightMemberDetails(member_number); ALTER TABLE TransactionDetails ADD CONSTRAINT transaction_number_drink_fk FOREIGN KEY (transaction_number) REFERENCES DrinkTransactionDetails(transaction_number); ALTER TABLE TransactionDetails ADD CONSTRAINT transaction_number_food_fk FOREIGN KEY (transaction_number) REFERENCES FoodTransactionDetails(transaction_number); ALTER TABLE TransactionDetails ADD CONSTRAINT movie_fk FOREIGN KEY (movie) REFERENCES MovieDetails (movie); Thank you for your help! If there is anything wrong with my database design please let me know! thank you!

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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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  • MySQL, delete and index hint

    - by Manuel Darveau
    I have to delete about 10K rows from a table that has more than 100 million rows based on some criteria. When I execute the query, it takes about 5 minutes. I ran an explain plan (the delete query converted to select * since MySQL does not support explain delete) and found that MySQL uses the wrong index. My question is: is there any way to tell MySQL which index to use during delete? If not, what ca I do? Select to temp table then delete from temp table? Thank you!

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  • Get latest record from second table left joined to first table

    - by codef0rmer
    I have a candidate table say candidates having only id field and i left joined profiles table to it. Table profiles has 2 fields namely, candidate_id & name. e.g. Table candidates: id 1 2 and Table `profiles`: candidate_id name 1 Foobar 1 Foobar2 2 Foobar3 i want the latest name of a candidate in a single query which is given below: SELECT C.id, P.name FROM candidates C LEFT JOIN profiles P ON P.candidate_id = C.id GROUP BY C.id ORDER BY P.name; But this query returns: 1 Foobar 2 Foobar3 Instead of: 1 Foobar2 2 Foobar3

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