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  • mysql join default value

    - by andy
    I've been trying to use the IsNull() function to ensure that there is a value for a field. $result = mysql_query(" SELECT crawled.id,IsNull(sranking.score,0) as Score,crawled.url,crawled.title,crawled.blurb FROM crawled LEFT JOIN sranking ON crawled.id = sranking.sid WHERE crawled.body LIKE '%".$term."%' ORDER BY Score DESC LIMIT " . $start . "," . $c . " ") or die(mysql_error()); But I get the error message:Incorrect parameter count in the call to native function 'IsNull' Anybody have any ideas? I'm pretty new to mySQL.

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  • MySQL Query Join Table Selecting Highest Date Value

    - by ALHUI
    Here is the query that I run SELECT cl.cl_id, cc_rego, cc_model, cl_dateIn, cl_dateOut FROM courtesycar cc LEFT JOIN courtesyloan cl ON cc.cc_id = cl.cc_id Results: 1 NXI955 Prado 2013-10-24 11:48:38 NULL 2 RJI603 Avalon 2013-10-24 11:48:42 2013-10-24 11:54:18 3 RJI603 Avalon 2013-10-24 12:01:40 NULL The results that I wanted are to group by the cc_rego values and print the most recent cl_dateIn value. (Only Display Rows 1,3) Ive tried to use MAX on the date and group by clause, but it combines rows, 2 & 3 together showing both the highest value of dateIn and dateOut. Any help will be appreciated.

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  • MySQL - Join as zero if record Not IN

    - by Zurahn
    To explain by example, take two tables, A and B Table A id foo 1 x 2 y 3 z Table B id aid bar 1 3 50 2 1 100 An example join SELECT foo, bar FROM a, b WHERE a.id = b.aid; Garners a result of foo bar z 50 x 100 What I would like to do is get all values of foo and for any instances where there isn't a corresponding bar value, return 0 for that column. My best guess was something along the lines of SELECT foo, bar AS br FROM a, b WHERE a.id = b.aid OR a.id NOT IN (SELECT aid FROM b); But that returns duplicates and non-zero values for bar. Possible?

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  • MYSQL: How to limit inner join?

    - by Sergii Rechmp
    I need some help with my query. I have 2 tables: all: art|serie sootv: name|art|foo I need to get result like name|serie. My query is: SELECT t2.NAME, t1.serie FROM ( SELECT * FROM `all` WHERE `serie` LIKE '$serie' ) t1 INNER JOIN sootv t2 ON t1.art = t2.art; it works, but sootv table contains data like name|art|foo abc | 1 | 5 abc | 1 | 6 i get 2 same results. Its not what i need. Help me please - how i can get only one result: abc|1 Thanks.

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  • Oracle SQL outer join query puzzle

    - by user1651446
    So I am dumb and I have this: select whatever from bank_accs b1, bank_accs b2, table3 t3 where t3.bank_acc_id = t1.bank_acc_id and b2.bank_acc_number = b1.bank_acc_number and b2.currency_code(+) = t3.buy_currency and trunc(sysdate) between nvl(b2.start_date, trunc(sysdate)) and nvl(b2.end_date, trunc(sysdate)); My problem is with the date (actuality) check on b2. Now, I need to return a row for each t3xb1 (t3 = ~10 tables joined, of course), even if there are ONLY INVALID records (date-wise) in b2. How do I outer-join this bit properly? Can't use ANSI joins, must do in a single flat query. Thanks.

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  • Sum of distinc rows after a 1-many table join

    - by Lock
    I have 2 tables that I am joining. Table 1 has 1-many relationship with table 2. That is, table 2 can return multiple rows for a single row of table 1. Because of this, the records of table 1 is duplicated for as many rows as are on table 2.. which is expected. Now, I have a sum on one of the columns from table 1, but because of the multiple rows that get returned on the join, the sum is obviously multiplying. Is there a way to get this number back to its original number? I tried dividing by the count of rows from table 2 but this didnt quite give me the expected result. Are there any analytical functions that could do this? I almost want something like "if this row has not yet been counted in the sum, add it to the sum"

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  • MySQL Join a Table if Exists Question

    - by swhitlow
    I have a DB which has a table called "config". This table could possibly have a "config_cstm" table that is related by the id to the config table. I was wondering - is there a way to dynamically check for the existence of this table in one simple select statement? In other words, something like: "select * from config (IF EXISTS config_cstm THEN LEFT OUTER JOIN config_cstm ON config.id = config_cstm.id_c" I know how I would go about checking for the existence of an existing table in PHP. I was wanting to do this all in one MySQL statement though. Any suggestions? Thanks!

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  • left join without duplicate values using MIN()

    - by Clipper87
    I have a table_1: id custno 1 1 2 2 3 3 and a table_2: id custno qty descr 1 1 10 a 2 1 7 b 3 2 4 c 4 3 7 d 5 1 5 e 6 1 5 f When I run this query to show the minimum order quantities from every customer: SELECT DISTINCT table_1.custno,table_2.qty,table_2.descr FROM table_1 LEFT OUTER JOIN table_2 ON table_1.custno = table_2.custno AND qty = (SELECT MIN(qty) FROM table_2 WHERE table_2.custno = table_1.custno ) Then I get this result: custno qty descr 1 5 e 1 5 f 2 4 c 3 7 d Customer 1 appears twice each time with the same minimum qty (& a different description) but I only want to see customer 1 appear once. I don't care if that is the record with 'e' as a description or 'f' as a description. How could I do this ? Thx!

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  • Count, inner join

    - by Urosh
    I have two tables: DRIVER (Driver_Id,First name,Last name,...) PARTICIPANT IN CAR ACCIDENT (Participant_Id,Driver_Id-foreign key,responsibility-yes or no,...) Now, I need to find out which driver participated in accident where responsibility is 'YES', and how many times. I did this: Select Driver_ID, COUNT (Participant.Driver_ID)as 'Number of accidents' from Participant in car accident where responsibility='YES' group by Driver_ID order by COUNT (Participant.Driver_ID) desc But, I need to add drivers first and last name from the first table(using inner join, I suppose). I don't know how, because it is not contained in either an aggregate function or the GROUP BY clause. Please help :)

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  • SQL SERVER – Subquery or Join – Various Options – SQL Server Engine knows the Best

    - by pinaldave
    This is followup post of my earlier article SQL SERVER – Convert IN to EXISTS – Performance Talk, after reading all the comments I have received I felt that I could write more on the same subject to clear few things out. First let us run following four queries, all of them are giving exactly same resultset. USE AdventureWorks GO -- use of = SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID = ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- use of in SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID IN ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- use of exists SELECT * FROM HumanResources.Employee E WHERE EXISTS ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- Use of Join SELECT * FROM HumanResources.Employee E INNER JOIN HumanResources.EmployeeAddress EA ON E.EmployeeID = EA.EmployeeID GO Let us compare the execution plan of the queries listed above. Click on image to see larger image. It is quite clear from the execution plan that in case of IN, EXISTS and JOIN SQL Server Engines is smart enough to figure out what is the best optimal plan of Merge Join for the same query and execute the same. However, in the case of use of Equal (=) Operator, SQL Server is forced to use Nested Loop and test each result of the inner query and compare to outer query, leading to cut the performance. Please note that here I no mean suggesting that Nested Loop is bad or Merge Join is better. This can very well vary on your machine and amount of resources available on your computer. When I see Equal (=) operator used in query like above, I usually recommend to see if user can use IN or EXISTS or JOIN. As I said, this can very much vary on different system. What is your take in above query? I believe SQL Server Engines is usually pretty smart to figure out what is ideal execution plan and use it. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Need help limiting a join in Transact-sql

    - by MsLis
    I'm somewhat new to SQL and need help with query syntax. My issue involves 2 tables within a larger multi-table join under Transact-SQL (MS SQL Server 2000 Query Analyzer) I have ACCOUNTS and LOGINS, which are joined on 2 fields: Site & Subset. Both tables may have multiple rows for each Site/Subset combination. ACCOUNTS: | LOGINS: SITE SUBSET FIELD FIELD FIELD | SITE SUBSET USERID PASSWD alpha bravo blah blah blah | alpha bravo foo bar alpha charlie blah blah blah | alpha bravo bar foo alpha charlie bleh bleh blue | alpha charlie id ego delta bravo blah blah blah | delta bravo john welcome delta foxtrot blah blah blah | delta bravo jane welcome | delta bravo ken welcome | delta bravo barbara welcome I want to select all rows in ACCOUNTS which have LOGIN entries, but only 1 login per account. DESIRED RESULT: SITE SUBSET FIELD FIELD FIELD USERID PASSWD alpha bravo blah blah blah foo bar alpha charlie blah blah blah id ego alpha charlie bleh bleh blue id ego delta bravo blah blah blah jane welcome I don't really care which row from the login table I get, but the UserID and Password have to correspond. [Don't return invalid combinations like foo/foo or bar/bar] MS Access has a handy FIRST function, which can do this, but I haven't found an equivalent in TSQL. Also, if it makes a difference, other tables are joined to ACCOUNTS, but this is the only use of LOGINS in the structure. Thank you very much for any assistance.

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  • Using named_scopes on the join model of a has_many :through

    - by uberllama
    Hi folks. I've been beating my head against the wall on something that on the surface should be very simple. Lets say I have the following simplified models: user.rb has_many :memberships has_many :groups, :through => :memberships membership.rb belongs_to :group belongs_to :user STATUS_CODES = {:admin => 1, :member => 2, :invited => 3} named_scope :active, :conditions => {:status => [[STATUS_CODES[:admin], STATUS_CODES[:member]]} group.rb has_many :memberships has_many :users, :through => :memberships Simple, right? So what I want to do is get a collection of all the groups a user is active in, using the existing named scope on the join model. Something along the lines of User.find(1).groups.active. Obviously this doesn't work. But as it stands, I need to do something like User.find(1).membrships.active.all(:include => :group) which returns a collection of memberships plus groups. I don't want that. I know I can add another has_many on the User model with conditions that duplicate the :active named_scope on the Membership model, but that's gross. has_many :active_groups, :through => :memberships, :source => :group, :conditions => ... So my question: is there a way of using intermediary named scopes when traversing directly between models? Many thanks.

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  • Join 3 tables in 1 LINQ-EF

    - by user100161
    I have to fill warehouse table cOrders with program using Ado.NET EF. I have SQL command but i don't know how to do this with LINQ. static void Main(string[] args) { var SPcontex = new PI_NorthwindSPEntities(); var contex = new NorthwindEntities(); dCustomers dimenzijaCustomers = new dCustomers(); dDatum dimenzijaDatum = new dDatum(); ... CREATE TABLE PoslovnaInteligencija.dbo.cOrders( cOrdersID int PRIMARY KEY IDENTITY(1,1), OrderID int NOT NULL, dCustomersID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dCustomers(dCustomersID), dEmployeesID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dEmployees(dEmployeesID), OrderDateID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dDatum(sifDatum), RequiredDateID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dDatum(sifDatum), ShippedDateID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dDatum(sifDatum), dShippersID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dShippers(dShippersID), dShipID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dShip(dShipID), Freight money, WaitingDay int ) INSERT INTO PoslovnaInteligencija.dbo.cOrders (OrderID, dCustomersID, dEmployeesID, OrderDateID, RequiredDateID, dShippersID, dShipID, Freight, ShippedDateID, WaitingDay) SELECT OrderID, dc.dCustomersID, de.dEmployeesID, orderD.sifDatum, requiredD.sifDatum, dShippersID, ds.dShipID, Freight, ShippedDateID=CASE WHEN (ShippedDate IS NULL) THEN -1 ELSE shippedD.sifDatum END, WaitingDay=CASE WHEN (shippedD.sifDatum - orderD.sifDatum) IS NULL THEN -1 ELSE shippedD.sifDatum - orderD.sifDatum END FROM PoslovnaInteligencija.dbo.dShippers AS s, PoslovnaInteligencija.dbo.dCustomers AS dc, PoslovnaInteligencija.dbo.dEmployees AS de, PoslovnaInteligencija.dbo.dShip AS ds,PoslovnaInteligencija.dbo.dDatum AS orderD, PoslovnaInteligencija.dbo.dDatum AS requiredD, PoslovnaInteligencija.dbo.Orders AS o LEFT OUTER JOIN PoslovnaInteligencija.dbo.dDatum AS shippedD ON shippedD.datum=DATEADD(dd, 0, DATEDIFF(dd, 0, o.ShippedDate)) WHERE o.ShipVia=s.ShipperID AND dc.CustomerID=o.CustomerID AND de.EmployeeID=o.EmployeeID AND ds.ShipName=o.ShipName AND orderD.datum=DATEADD(dd, 0, DATEDIFF(dd, 0, o.OrderDate)) AND requiredD.datum=DATEADD(dd, 0, DATEDIFF(dd, 0, o.RequiredDate));

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  • Dynamic where clause using Linq to SQL in a join query in a MVC application

    - by jhoefnagels
    Dear .Net Linq experts, I am looking for a way to query for products in a catalog using filters on properties which have been assigned to the product based on the category to which the product belongs. So I have the following entities involved: Products -Id -CategoryId Categories [Id] Properties [Id, CategoryId] PropertyValues [Id, PropertyId] ProductProperties [ProductId, PropertyValueId] When I ad a product to the catalog, multiple ProductProperties will be added based on the category and I would like to be able to filter all products from a category by selecting values for one or more properties. I will gather all filters, which I will hold in a list, by reading the URL. Now it is time to actually get the products based on multiple properties and I have been trying to find the right strategy but untill now it does not really work. Is there a way to make this work without writing SQL? I was trying something like this: productsInCategory = ProductRepository.Where(p => p.Category.Name == category); foreach (PropertyFilter pf in filterList) { productsInCategory = (from product in productsInCategory join pp in ProductPropertyRepository on product.Id equals pp.ProductId where pp.PropertyValueId == pf.ValueId select product); }

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  • Converting Complicated Oracle Join Syntax

    - by Grasper
    I have asked for help before on porting joins of this nature, but nothing this complex. I am porting a bunch of old SQL from oracle to postgres, which includes a lot of (+) style left joins. I need this in a format that pg will understand. I am having trouble deciphering this join hierarchy: SELECT * FROM PLANNED_MISSION PM_CTRL, CONTROL_AGENCY CA, MISSION_CONTROL MC, MISSION_OBJECTIVE MOR, REQUEST_OBJECTIVE RO, MISSION_REQUEST_PAIRING MRP, FRIENDLY_UNIT FU, PACKAGE_MISSION PKM, MISSION_AIRCRAFT MA, MISSION_OBJECTIVE MO, PLANNED_MISSION PM WHERE PM.MSN_TASKED_UNIT_TYPE != 'EAM' AND PM.MSN_INT_ID = MO.MSN_INT_ID AND PM.MSN_INT_ID = PKM.MSN_INT_ID (+) AND PM.MSN_INT_ID = MA.MSN_INT_ID (+) AND COALESCE(MA.MA_RESOURCE_INT_ID,0) = (SELECT COALESCE(MIN(MA1.MA_RESOURCE_INT_ID),0) FROM MISSION_AIRCRAFT MA1 WHERE MA.MSN_INT_ID = MA1.MSN_INT_ID) AND MA.FU_UNIT_ID = FU.FU_UNIT_ID (+) AND MA.CC_COUNTRY_CD = FU.CC_COUNTRY_CD (+) AND MO.MSN_INT_ID = MC.MSN_INT_ID (+) AND MO.MO_INT_ID = MC.MO_INT_ID (+) AND MC.CAG_CALLSIGN = CA.CAG_CALLSIGN (+) AND MC.CTRL_MSN_INT_ID = PM_CTRL.MSN_INT_ID (+) AND MO.MSN_INT_ID = MRP.MSN_INT_ID (+) AND MO.MO_INT_ID = MRP.MO_INT_ID (+) AND MRP.REQ_INT_ID = RO.REQ_INT_ID (+) AND RO.MSN_INT_ID = MOR.MSN_INT_ID (+) AND RO.MO_INT_ID = MOR.MO_INT_ID (+) AND MO.MSN_INT_ID = :msn_int_id AND MO.MO_INT_ID = :obj_int_id AND COALESCE(PM.MSN_MISSION_NUM, ' ') LIKE '%' AND COALESCE( PKM.PKG_NM,' ') LIKE '%' AND COALESCE( MA.FU_UNIT_ID, ' ') LIKE '%' AND COALESCE( MA.CC_COUNTRY_CD, ' ') LIKE '%' AND COALESCE(FU.FU_COMPONENT, ' ') LIKE '%' AND COALESCE( MA.ACT_AC_TYPE,' ') LIKE '%' AND MO.MO_MSN_CLASS_CD LIKE '%' AND COALESCE(MO.MO_MSN_TYPE, ' ') LIKE '%' AND COALESCE( MO.MO_OBJ_LOCATION,COALESCE( MOR.MO_OBJ_LOCATION, ' ')) LIKE '%' AND COALESCE(CA.CAG_TYPE_OF_CONTROL, ' ') LIKE '%' AND COALESCE( MC.CAG_CALLSIGN,' ') LIKE '%' AND COALESCE( MC.ASP_AIRSPACE_NM, ' ') LIKE '%' AND COALESCE( MC.CTRL_MSN_INT_ID, 0) LIKE '%' AND COALESCE(MC.CTRL_MO_INT_ID, 0) LIKE '%' AND COALESCE( PM_CTRL.MSN_MISSION_NUM,' ') LIKE '%' Any help is appreciated.

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  • SQLite self-join performance

    - by Derk
    What I essentially want, is to retreive all features and values of products which have a particular feature and value. For example: I want to know all available hard drive sizes of products that have an Intel processor. I have three tables: product_to_value (product_id, feature_id, value_id) features (id, value) // for example Processor family, Storage size, etc. values (id, value) // for example Intel, 60GB, etc The simplified query I have now: SELECT features.name, featurevalues.name, featurevalues.value FROM products, products as prod2, features, features as feat2, values, values as val2 WHERE products.feature = features.id AND products.value = values.id AND products.product = prod2.product AND prod2.feature_id = feat2.id AND prod2.value_id = val2.id AND features.id = ? AND feat2.id = ? All columns have an index. I am using SQLite. The problem is that it's very slow (70ms per query, without the self-join it's <1ms). Is there a smarter way to fetch data like this? Or is this too much to ask from SQLite? I personally think I am simply overlooking something, as I am quite new to SQLite.

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  • SQL Inner Join : DB stuck

    - by SurfingCat
    I postet this question a few days ago but I didn't explain exactly what I want. I ask the question better formulated again: To clarify my problem I added some new information: I got an MySQL DB with MyISAM tables. The two relevant tables are: * orders_products: orders_products_id, orders_id, product_id, product_name, product_price, product_name, product_model, final_price, ... * products: products_id, manufacturers_id, ... (for full information about the tables see screenshot products (Screenshot) and screenshot orders_products (Screenshot)) Now what I want is this: - Get all Orders who ordered products with manufacturers_id = 1. And the product name of the product of this order (with manufacturers_id = 1). Grouped by orders. What I did so far is this: SELECT op.orders_id, p.products_id, op.products_name, op.products_price, op.products_quantity FROM orders_products op , products p INNER JOIN products ON op.products_id = p.products_id WHERE p.manufacturers_id = 1 AND p.orders_id > 10000 p.orders_id 10000 for testing to get only a few order_id's. But thies query takes much time to get executed if it even works. Two times the sql server stucked. Where is the mistake?

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  • MySQL: Complex Join Statement involving two tables and a third correlation table

    - by Stephen
    I have two tables that were built for two disparate systems. I have records in one table (called "leads") that represent customers, and records in another table (called "manager") that are the exact same customers but "manager" uses different fields (For example, "leads" contains an email address, and "manager" contains two fields for two different emails--either of which might be the email from "leads"). So, I've created a correlation table that contains the lead_id and manager_id. currently this correlation table is empty. I'm trying to query the "leads" table to give me records that match either "manager" email field with the single "leads" email field, while at the same time ignoring fields that have already been added to the "correlated" table. (this way I can see how many leads that match have not yet been correlated.) Here's my current, invalid SQL attempt: SELECT leads.id, manager.id FROM leads, manager LEFT OUTER JOIN correlation ON correlation.lead_id = leads.id WHERE correlation.id IS NULL AND leads.project != "someproject" AND (manager.orig_email = leads.email OR manager.dest_email = leads.email) AND leads.created BETWEEN '1999-01-01 00:00:00' AND '2010-05-10 23:59:59' ORDER BY leads.created ASC; I get the error: Unknown column 'leads.id' in 'on clause' Before you wonder: there are records in the "leads" table where leads.project != "someproject" and leads.created falls between those dates. I've included those additional parameters for completeness.

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  • django join-like expansion of queryset

    - by jimbob
    I have a list of Persons each which have multiple fields that I usually filter what's upon, using the object_list generic view. Each person can have multiple Comments attached to them, each with a datetime and a text string. What I ultimately want to do is have the option to filter comments based on dates. class Person(models.Model): name = models.CharField("Name", max_length=30) ## has ~30 other fields, usually filtered on as well class Comment(models.Model): date = models.DateTimeField() person = models.ForeignKey(Person) comment = models.TextField("Comment Text", max_length=1023) What I want to do is get a queryset like Person.objects.filter(comment__date__gt=date(2011,1,1)).order_by('comment__date') send that queryset to object_list and be able to only see the comments ordered by date with only so many objects on a page. E.g., if "Person A" has comments 12/3/11, 1/2/11, 1/5/11, "Person B" has no comments, and person C has a comment on 1/3, I would see: "Person A", 1/2 - comment "Person C", 1/3 - comment "Person A", 1/5 - comment I would strongly prefer not to have to switch to filtering based on Comments.objects.filter(), as that would make me have to largely repeat large sections of code in the both the view and template. Right now if I tried executing the following command, I will get a queryset returning (PersonA, PersonC, PersonA), but if I try rendering that in a template each persons comment_set will contain all their comments even if they aren't in the date range. Ideally they're would be some sort of functionality where I could expand out a Person queryset's comment_set into a larger queryset that can be sorted and ordered based on the comment and put into a object_list generic view. This normally is fairly simple to do in SQL with a JOIN, but I don't want to abandon the ORM, which I use everywhere else.

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  • Mysql slow query: INNER JOIN + ORDER BY causes filesort

    - by Alexander
    Hello! I'm trying to optimize this query: SELECT `posts`.* FROM `posts` INNER JOIN `posts_tags` ON `posts`.id = `posts_tags`.post_id WHERE (((`posts_tags`.tag_id = 1))) ORDER BY posts.created_at DESC; The size of tables is 38k rows, and 31k and mysql uses "filesort" so it gets pretty slow. I tried to use different indexes, no luck. CREATE TABLE `posts` ( `id` int(11) NOT NULL auto_increment, `created_at` datetime default NULL, PRIMARY KEY (`id`), KEY `index_posts_on_created_at` (`created_at`), KEY `for_tags` (`trashed`,`published`,`clan_private`,`created_at`) ) ENGINE=InnoDB AUTO_INCREMENT=44390 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci CREATE TABLE `posts_tags` ( `id` int(11) NOT NULL auto_increment, `post_id` int(11) default NULL, `tag_id` int(11) default NULL, `created_at` datetime default NULL, `updated_at` datetime default NULL, PRIMARY KEY (`id`), KEY `index_posts_tags_on_post_id_and_tag_id` (`post_id`,`tag_id`) ) ENGINE=InnoDB AUTO_INCREMENT=63175 DEFAULT CHARSET=utf8 +----+-------------+------------+--------+--------------------------+--------------------------+---------+---------------------+-------+-----------------------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+------------+--------+--------------------------+--------------------------+---------+---------------------+-------+-----------------------------------------------------------+ | 1 | SIMPLE | posts_tags | index | index_post_id_and_tag_id | index_post_id_and_tag_id | 10 | NULL | 24159 | Using where; Using index; Using temporary; Using filesort | | 1 | SIMPLE | posts | eq_ref | PRIMARY | PRIMARY | 4 | .posts_tags.post_id | 1 | | +----+-------------+------------+--------+--------------------------+--------------------------+---------+---------------------+-------+-----------------------------------------------------------+ 2 rows in set (0.00 sec) What kind of index I need to define to avoid mysql using filesort? Is it possible when order field is not in where clause?

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  • How can I manage a fork pool in Perl?

    - by user301087
    I'm setting something up to SSH out to several servers in 'batches'. I basically want to maintain 5 connections at a time, and when one finishes open up another (following an array of server IPs). I'm wondering for something like this should I be using fork()? If so, what logic can I use to ensure that the I maintain 5 children at a time?

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