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  • Removing "Using temporary; Using filesort" from this MySQL select+join+group by query

    - by claytontstanley
    I have the following query: select t.Chunk as LeftChunk, t.ChunkHash as LeftChunkHash, q.Chunk as RightChunk, q.ChunkHash as RightChunkHash, count(t.ChunkHash) as ChunkCount from chunksubset as t join chunksubset as q on t.ID = q.ID group by LeftChunkHash, RightChunkHash And the following explain table: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE subsets ref PRIMARY,IDIndex,SubsetIndex SubsetIndex 767 const 522014 "Using where; Using temporary; Using filesort" 1 SIMPLE subsets eq_ref PRIMARY,IDIndex,SubsetIndex PRIMARY 771 sotero.subsets.Id,const 1 "Using where; Using index" 1 SIMPLE c ref IDIndex IDIndex 4 sotero.subsets.Id 12 "Using where" 1 SIMPLE c ref IDIndex IDIndex 4 sotero.subsets.Id 12 note the "using temporary; using filesort". When this query is run, I quickly run out of RAM (presumably b/c of the temp table), and then the HDD kicks in, and the query slows to a halt. I thought it might be an index issue, so I started adding a few that sort of made sense: Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment chunks 0 PRIMARY 1 ChunkId A 17796190 NULL NULL BTREE chunks 1 ChunkHashIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 IDIndex 1 Id A 1483015 NULL NULL BTREE chunks 1 ChunkIndex 1 Chunk A 243783 NULL NULL BTREE chunks 1 ChunkTypeIndex 1 ChunkType A 2 NULL NULL BTREE chunks 1 chunkHashByChunkIDIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 chunkHashByChunkIDIndex 2 ChunkId A 17796190 NULL NULL BTREE chunks 1 chunkHashByChunkTypeIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 chunkHashByChunkTypeIndex 2 ChunkType A 261708 NULL NULL BTREE chunks 1 chunkHashByIDIndex 1 ChunkHash A 243783 NULL NULL BTREE chunks 1 chunkHashByIDIndex 2 Id A 17796190 NULL NULL BTREE But still using the temporary table. The db engine is MyISAM. How can I get rid of the using temporary; using filesort in this query? Just changing to InnoDB w/o explaining the underlying cause is not a particularly satisfying answer. Besides, if the solution is to just add the proper index, then that's much easier than migrating to another db engine.

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  • Optimize a MySQL count each duplicate Query

    - by Onema
    I have the following query That gets the city name, city id, the region name, and a count of duplicate names for that record: SELECT Country_CA.City AS currentCity, Country_CA.CityID, globe_region.region_name, ( SELECT count(Country_CA.City) FROM Country_CA WHERE City LIKE currentCity ) as counter FROM Country_CA LEFT JOIN globe_region ON globe_region.region_id = Country_CA.RegionID AND globe_region.country_code = Country_CA.CountryCode ORDER BY City This example is for Canada, and the cities will be displayed on a dropdown list. There are a few towns in Canada, and in other countries, that have the same names. Therefore I want to know if there is more than one town with the same name region name will be appended to the town name. Region names are found in the globe_region table. Country_CA and globe_region look similar to this (I have changed a few things for visualization purposes) CREATE TABLE IF NOT EXISTS `Country_CA` ( `City` varchar(75) NOT NULL DEFAULT '', `RegionID` varchar(10) NOT NULL DEFAULT '', `CountryCode` varchar(10) NOT NULL DEFAULT '', `CityID` int(11) NOT NULL DEFAULT '0', PRIMARY KEY (`City`,`RegionID`), KEY `CityID` (`CityID`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; AND CREATE TABLE IF NOT EXISTS `globe_region` ( `country_code` char(2) COLLATE utf8_unicode_ci NOT NULL, `region_code` char(2) COLLATE utf8_unicode_ci NOT NULL, `region_name` varchar(50) COLLATE utf8_unicode_ci NOT NULL, PRIMARY KEY (`country_code`,`region_code`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; The query on the top does exactly what I want it to do, but It takes way too long to generate a list for 5000 records. I would like to know if there is a way to optimize the sub-query in order to obtain the same results faster. the results should look like this City CityID region_name counter sheraton 2349269 British Columbia 1 sherbrooke 2349270 Quebec 2 sherbrooke 2349271 Nova Scotia 2 shere 2349273 British Columbia 1 sherridon 2349274 Manitoba 1

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  • DB2: Won't allow parameterize fetch first X rows only

    - by Guy Roth
    Although in Oracle DB its is allowed to parametrize the number of rows that the query can fetch by adding to the query: select ... from ... where ... and rownum <= @MaximumRecords I can't add similar condition to acuivalent query running in DB2: It is allowed to add: select ... from ... where ... fetch first 500 rows only (where there is fixed number of rows) but not: select ... from ... where ... fetch first :1 rows only (:1 == @MaximumRecords) Is someone aware of a solution/work-around to this problem?

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  • Oracle SQL CMD Line!!!

    - by DAVID
    Hi when ever perform select statements in the command line tool it doesnt use all of the space.. ive modified buffer size and window size and it just doesnt work. here is the Screenshot http://img19.imageshack.us/img19/8954/cmdoracle.jpg

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  • Need help with a conditional SELECT statement

    - by Ethan
    I've got a stored procedure with a select statement, like this: `SELECT author_ID, author_name, author_bio FROM Authors WHERE author_ID in (SELECT author_ID from Books) ` This limits results to authors who have book records. This is the Books table: Books book_ID INT author_ID INT book_title NVARCHAR featured_book BIT What I want to do is conditionally select the ID of the featured book by each author as part of the select statement above, and if none of the books for a given author are featured, select the ID of the first (top 1) book by the author from the books table. How do I approach this?

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  • How can I get the rank of rows relative to total number of rows based on a field?

    - by Arms
    I have a scores table that has two fields: user_id score I'm fetching specific rows that match a list of user_id's. How can I determine a rank for each row relative to the total number of rows, based on score? The rows in the result set are not necessarily sequential (the scores will vary widely from one row to the next). I'm not sure if this matters, but user_id is a unique field. Edit @Greelmo I'm already ordering the rows. If I fetch 15 rows, I don't want the rank to be 1-15. I need it to be the position of that row compared against the entire table by the score property. So if I have 200 rows, one row's rank may be 3 and another may be 179 (these are arbitrary #'s for example only). Edit 2 I'm having some luck with this query, but I actually want to avoid ties SELECT s.score , s.created_at , u.name , u.location , u.icon_id , u.photo , (SELECT COUNT(*) + 1 FROM scores WHERE score > s.score) AS rank FROM scores s LEFT JOIN users u ON u.uID = s.user_id ORDER BY s.score DESC , s.created_at DESC LIMIT 15 If two or more rows have the same score, I want the latest one (or earliest - I don't care) to be ranked higher. I tried modifying the subquery with AND id > s.id but that ended up giving me an unexpected result set and different ties.

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  • using dummy row with NOT NULL to solve DEFAULT 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 colunms. I have the first row in every lookup 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 PK =1 for FKs which do not have any lookup value. Is this a good design or any other work arounds? EDIT: I have: Neighborhood table Postal table. Every neighborhood has a city, so the FK can be NOT NULL. But not every postal code belongs to a neighborhood. Some do, some don't depending on the country. So if i use NOT NULL for the FK between postal and neighborhood then I will be screwed as there has to be some value entered. So what i am doing in essence is: have a row in every table to be a dummy row just to link the FKs. This way row one in neighborhood table will be: n_id = 1 name =none etc... In postal table I can have: postal_code = 3456A3 FK (city) = Moscow FK (neighborhood_id)=1 as a NOT NULL. If I don't have a dummy row in the neighborhood lookup table then I have to declare FK (neighborhood_id) as a Default null column and store blanks in the table. This is an example but there is a huge number of values which will have blanks then in many tables.

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  • Updating records in Postgres using FROM clause

    - by Summer
    Hi, I'm changing my db schema, and moving column 'seat' from old_table to new_table. First I added a 'seat' column to new_table. Now I'm trying to populate the column with the values from old_table. UPDATE new_table SET seat = seat FROM old_table WHERE old_table.id = new_table.ot_id; This returns ERROR: column reference "seat" is ambiguous. UPDATE new_table nt SET nt.seat = ot.seat FROM old_table ot WHERE ot.id = nt.ot_id; Returns ERROR: column "nt" of relation "new_table" does not exist Ideas?

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  • How to connect 2 mysql tables with 2 connection string

    - by denonth
    Hi all I need to connect 2 tables from 2 mysql databases that have 2 different connection strings and each is on the different server. I have this query: cmd = new MySqlCommand(String.Format("INSERT INTO {0} (a,b,c,d) SELECT (a,b,c,d) FROM {1}", ConfigSettings.ReadSetting("main_table"), ConfigSettings.ReadSetting("main_table")), con); So both table have the same columns. Thats why I have only one ConfigSettings.ReadSetting("main_table") for both of them as they are same. I have 2 connection strings and each is pointing to their server: con.ConnectionString = ConfigurationManager.ConnectionStrings["con1"].ConnectionString; con2.ConnectionString = ConfigurationManager.ConnectionStrings["con2"].ConnectionString; How to make this cmd to be workking with 2 different connection strings and with the same name for the table. Table name will change that's why it is saved in config.

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  • Syntax for "RETURNING" clause in Mysql PDO

    - by dmontain
    I'm trying to add a record, and at the same time return the id of that record added. I read it's possible to do it with a RETURNING clause. $stmt->prepare("INSERT INTO tablename (field1, field2) VALUES (:value1, :value2) RETURNING id"); but the insertion fails when I add RETURNING. There is an auto-incremented field called id in the table being added to. Can someone see anything wrong with my syntax? or maybe PDO does not support RETURNING?

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  • when i download file from my website which contains grid and in one of the column of grid there is d

    - by SmartDev
    Hi, I have page called filedownload.aspx , it contains grid and in grid they are three columns and in one of the column there is button which says Download , when user clicks on that button it picks file id and gives the download box to user with three options Open save and cancel . Now the problem is that when user clicks on the download button in grid it gives this ERROR: INTERNET EXPLORER CANNOT DOWNLOAD FILEDOWNLOAD.ASPX FROM ABC.XYZ.COM (MY URL EXAMPLE) INTERNET EXPLORER WAS NOT ABLE TO OPEN THIS SITE .THE REQUEST SITE IS EITHER UNAVAILABLE OR CANNOT BE FOUND . ONE MORE THING IS THT RECENTLY WE IMPLEMENTED SSL AND FROM HTTP WE MOVE TO HTTPS WITH NAME CHANGE IN URL ALSO BFEORE IT WAS AND NOW ITS . NOW WHEN I CHANGE THE URL TO OLD ONE THE PAGE IS WORKING FINE . CAN ANYONE HELP ME ON THIS ? THANKS, SMARTDEV

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  • Syntax Error with MySQL 5.1 Server

    - by Mr.Z
    I am trying to connect to a server remotely using the command line client window. I am using MySQL 5.1 and I do not know why I am getting syntax error. If you can help me, that would be much appreciated. username as user password as pass hostname as example.com I have tried: mysql> -u user -h example.com -p ; mysql> -h example.com -u user -p ; I have looked at the reference manual and other verisons of remote connection with Server 5.1 but I can't see the syntax error.

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  • Oracle - Updating one column or another based on a condition

    - by z-dan
    I want to update a record in a table but based on a condition I will either update one column or another but I do not want to have 2 separate statements because the statements are very long and detailed. Here is the basic idea with over simplification to get to the point. PROCEDURE Animal_something(p_updater VARCHAR2) begin if p_updater = 'person' then -- I want to update the modified_by else -- if p_updater = 'a process' I want to update modified_by_process Update table_creatures set animal_type = 'Dog , **modified_by** = 'Bob' **or do this** **modified_by_process =** 'creature_package' where animal_legs = '4' I don't want: if p_updater = 'person' then Update table_creatures set animal_type = 'Dog , modified_by = 'Bob' where animal_legs = '4'; else Update table_creatures set animal_type = 'Dog , modified_by_process = 'creature_package' where animal_legs = '4'; end;

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  • Using NULLs in matchup table

    - by TomWilsonFL
    I am working on the accounting portion of a reservation system (think limo company). In the system there are multiple objects that can either be paid or submit a payment. I am tracking all of these "transactions" in three tables called: tx, tx_cc, and tx_ch. tx generates a new tx_id (for transaction ID) and keeps the information about amount, validity, etc. Tx_cc and tx_ch keep the information about the credit card or check used, respectively, which link to other tables (credit_card and bank_account among others). This seems fairly normalized to me, no? Now here is my problem: The payment transaction can take place for a myriad of reasons. Either a reservation is being paid for, a travel agent that booked a reservation is being paid, a driver is being paid, etc. This results in multiple tables, one for each of the entities: agent_tx, driver_tx, reservation_tx, etc. They look like this: CREATE TABLE IF NOT EXISTS `driver_tx` ( `tx_id` int(10) unsigned zerofill NOT NULL, `driver_id` int(11) NOT NULL, `reservation_id` int(11) default NULL, `reservation_item_id` int(11) default NULL, PRIMARY KEY (`tx_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; Now this transaction is for a driver, but could be applied to an individual item on the reservation or the entire reservation overall. Therefore I demand either reservation_id OR reservation_item_id to be null. In the future there may be other things which a driver is paid for, which I would also add to this table, defaulting to null. What is the rule on this? Opinion? Obviously I could break this out into MANY three column tables, but the amount of OUTER JOINing needed seems outrageous. Your input is appreciated. Peace, Tom

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  • How to structure the tables of a very simple blog in MySQL?

    - by Programmer
    I want to add a very simple blog feature on one of my existing LAMP sites. It would be tied to a user's existing profile, and they would be able to simply input a title and a body for each post in their blog, and the date would be automatically set upon submission. They would be allowed to edit and delete any blog post and title at any time. The blog would be displayed from most recent to oldest, perhaps 20 posts to a page, with proper pagination above that. Other users would be able to leave comments on each post, which the blog owner would be allowed to delete, but not pre-moderate. That's basically it. Like I said, very simple. How should I structure the MySQL tables for this? I'm assuming that since there will be blog posts and comments, I would need a separate table for each, is that correct? But then what columns would I need in each table, what data structures should I use, and how should I link the two tables together (e.g. any foreign keys)? I could not find any tutorials for something like this, and what I'm looking to do is really offer my users the simplest version of a blog possible. No tags, no moderation, no images, no fancy formatting, etc. Just a simple diary-type, pure-text blog with commenting by other users.

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  • Better way to do SELECT with GROUP BY

    - by Luca Romagnoli
    Hi i've wrote a query that works: SELECT `comments`.* FROM `comments` RIGHT JOIN (SELECT MAX( id ) AS id, core_id, topic_id FROM comments GROUP BY core_id, topic_id order by id desc) comm ON comm.id = comments.id LIMIT 10 I want know if it is possible (and how) to rewrite it to get better performance. Thanks

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  • How to get an id from the results in two tables

    - by Chris Lively
    Consider an order. An order will have one or more line items. Each line item is for a particular product. Given a filter table with a couple of products, how would I get the order id's that had at least all of the products listed in the second table? table Orders( OrderId int ) table LineItems ( OrderId int, LineItemId int, ProductId int ) table Filter ( ProductId int ) data Orders OrderId -------- 1 2 3 LineItems OrderId LineItemId ProductId ------- ---------- --------- 1 1 401 1 2 502 2 3 401 3 4 401 3 5 603 3 6 714 Filter ProductId --------- 401 603 Desired result of the query: OrderId: 3

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  • LINQtoSQL: Query to return List<String>

    - by ctrlShiftBryan
    I have a LINQ query that returns some object like this... var query = from c in db.Customers where ... select c; Then I do this List<String> list = new List<String>(); foreach (ProgramLanguage c in query) { //GetUL returns a String list.Add(GetUL(c.Property,c.Property2)); } Is there a way to combine into something list this? var query = from c in db.Customers where ... select new { GetUL(c.Property,c.Property2) }).ToList<String>();

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  • Sqlite and Python -- return a dictionary using fetchone()?

    - by AndrewO
    I'm using sqlite3 in python 2.5. I've created a table that looks like this: create table votes ( bill text, senator_id text, vote text) I'm accessing it with something like this: v_cur.execute("select * from votes") row = v_cur.fetchone() bill = row[0] senator_id = row[1] vote = row[2] What I'd like to be able to do is have fetchone (or some other method) return a dictionary, rather than a list, so that I can refer to the field by name rather than position. For example: bill = row['bill'] senator_id = row['senator_id'] vote = row['vote'] I know you can do this with MySQL, but does anyone know how to do it with SQLite? Thanks!!!

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