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  • using joins or multiple queries in php/mysql

    - by askkirati
    Here i need help with joins. I have two tables say articles and users. while displaying articles i need to display also the user info like username, etc. So will it be better if i just use joins to join the articles and user tables to fetch the user info while displaying articles like below. SELECT a.*,u.username,u.id FROM articles a JOIN users u ON u.id=a.user_id OR can this one in php. First i get the articles with below sql SELECT * FROM articles Then after i get the articles array i loop though it and get the user info inside each loop like below SELECT username, id FROM users WHERE id='".$articles->user_id."'; Which is better can i have explanation on why too. Thank you for any reply or views

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  • SQL joins "going up" two tables

    - by blcArmadillo
    I'm trying to create a moderately complex query with joins: SELECT `history`.`id`, `parts`.`type_id`, `serialized_parts`.`serial`, `history_actions`.`action`, `history`.`date_added` FROM `history_actions`, `history` LEFT OUTER JOIN `parts` ON `parts`.`id` = `history`.`part_id` LEFT OUTER JOIN `serialized_parts` ON `serialized_parts`.`parts_id` = `history`.`part_id` WHERE `history_actions`.`id` = `history`.`action_id` AND `history`.`unit_id` = '1' ORDER BY `history`.`id` DESC I'd like to replace `parts`.`type_id` in the SELECT statement with `part_list`.`name` where the relationship I need to enforce between the two tables is `part_list`.`id` = `parts`.`type_id`. Also I have to use joins because in some cases `history`.`part_id` may be NULL which obviously isn't a valid part id. How would I modify the query to do this?

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  • SQL Server Multiple Joins Are Taxing The CPU

    - by durilai
    I have a stored procedure on SQL Server 2005. It is pulling from a Table function, and has two joins. When the query is run using a load test it kills the CPU 100% across all 16 cores! I have determined that removing one of the joins makes the query run fine, but both taxes the CPU. Select SKey From dbo.tfnGetLatest(@ID) a left join [STAGING].dbo.RefSrvc b on a.LID = b.ESIID left join [STAGING].dbo.RefSrvc c on a.EID = c.ESIID Any help is appreciated, note the join is happening on the same table in a different database on the same server.

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  • Need an alternative to two left joins.

    - by Scarface
    Hey guys quick question, I always use left join, but when I left join twice I always get funny results, usually duplicates. I am currently working on a query that Left Joins twice to retrieve the necessary information needed but I was wondering if it were possible to build another select statement in so then I do not need two left joins or two queries or if there were a better way. For example, if I could select the topic.creator in table.topic first AS something, then I could select that variable in users and left join table.scrusersonline. Thanks in advance for any advice. SELECT * FROM scrusersonline LEFT JOIN users ON users.id = scrusersonline.id LEFT JOIN topic ON users.username = topic.creator WHERE scrusersonline.topic_id = '$topic_id' The whole point of this query is to check if the topic.creator is online by retrieving his name from table.topic and matching his id in table.users, then checking if he is in table.scrusersonline. It produces duplicate entries unfortunately and is thus inaccurate in my mind.

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  • Multiple Table Joins to Improve Performance?

    - by EdenMachine
    If I have a table structure like this: Transaction [TransID, ...] Document [DocID, TransID, ...] Signer [SignerID, ...] Signature [SigID, DocID, SignerID, ...] And the business logic is like this: Transactions can have multiple documents Documents can have multiple signatures And the same signer can have multiple signatures in multiple documents within the same transaction So, now to my actual question: If I wanted to find all the documents in a particular transaction, would it be better, performance-wise, if I also stored the TransID and the DocID in the Signer table as well so I have smaller joins. Otherwise, I'd have to join through the Signature Document Transaction Documents to get all the documents in the transaction for that signer. I think it's really messy to have that many relationships in the Signer table though and it doesn't seem "correct" to do it that way (also seems like an update nightmare) but I can see that it might be better performance for direct joins. Thoughts? TIA!

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  • Left outer joins that don't return all the rows from T1

    - by Summer
    Left outer joins should return at least one row from the T1 table if it matches the conditions. But what if the left outer join performs a join successfully, then finds that another criterion is not satisfied? Is there a way to get the query to return a row with T1 values and T2 values set to NULL? Here's the specific query, in which I'm trying to return a list of candidates, and the user's support for those candidates IF such support exists. SELECT c.id, c.name, s.support FROM candidates c LEFT JOIN support s on s.candidate_id = c.id WHERE c.office_id = 5059 AND c.election_id = 92 AND (s.user_id = 2 OR s.user_id IS NULL) --This line seems like the problem ORDER BY c.last_name, c.name The query joins the candidates and support table, but finds that it's a different user who supported this candidate (user_id=3, say). Then the candidate disappears entirely from the result set.

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  • Avoiding secondary selects or joins with Hibernate Criteria or HQL query

    - by Ben Benson
    I am having trouble optimizing Hibernate queries to avoid performing joins or secondary selects. When a Hibernate query is performed (criteria or hql), such as the following: return getSession().createQuery(("from GiftCard as card where card.recipientNotificationRequested=1").list(); ... and the where clause examines properties that do not require any joins with other tables... but Hibernate still performs a full join with other tables (or secondary selects depending on how I set the fetchMode). The object in question (GiftCard) has a couple ManyToOne associations that I would prefer to be lazily loaded in this case (but not necessarily all cases). I want a solution that I can control what is lazily loaded when I perform the query. Here's what the GiftCard Entity looks like: @Entity @Table(name = "giftCards") public class GiftCard implements Serializable { private static final long serialVersionUID = 1L; private String id_; private User buyer_; private boolean isRecipientNotificationRequested_; @Id public String getId() { return this.id_; } public void setId(String id) { this.id_ = id; } @ManyToOne @JoinColumn(name = "buyerUserId") @NotFound(action = NotFoundAction.IGNORE) public User getBuyer() { return this.buyer_; } public void setBuyer(User buyer) { this.buyer_ = buyer; } @Column(name="isRecipientNotificationRequested", nullable=false, columnDefinition="tinyint") public boolean isRecipientNotificationRequested() { return this.isRecipientNotificationRequested_; } public void setRecipientNotificationRequested(boolean isRecipientNotificationRequested) { this.isRecipientNotificationRequested_ = isRecipientNotificationRequested; } }

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  • Performance of Multiple Joins

    - by geeko
    Greetings Overflowers, I need to query against objects with many/complex spacial conditions. In relational databases that is translated to many joins (possibly 10+). I'm new to this business and wondering whether to go with MS SQL Server 2008 R2 or Oracle 11g or document-based solutions such as RavenDB or simply go with some spacial database (GIS)... Any thoughts ? Regards UPDATE: Thank you all for your answers. Would anybody opt for document/spatial databases ? My database would consist of tens of millions to few billion records. Mostly read-only. Almost no updates unless in case of mistakes in input. Overnight inserts and not that frequent. The join tables are predicted beforehand but the number of self joins (tables joining themselves multiple times) is not. Small pages of results from such queries are going to be viewed on an highly interactive website so response time is critical. Any predictions on how this can perform on MS SQL Server 2008 R2 or Oracle 11g ? I'm also concerned about boosting performance by adding more servers, which one scales better ? How about PostgresQL ?

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  • Explain to a Jr. SysAdmin what happens when a PC joins a Windows 2008 Domain

    - by Nimmy Lebby
    An ideal answer would at least include: Critical configuration of the PC before it could join How the PC finds the Domain servers What happens when the PC cannot find any domain servers What connections are made from the PC to the domain How the AD records the connection How the PC drops the connection/AD monitors for stale connections Difference in this process between Windows 2008 R2 and previous versions of Windows Server That is all I could think of for now but I'm sure, as answers come in, I'll think of more.

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  • Slow RDP after server joins domain

    - by Chris Grove
    We're having RDP issues with Amazon cloud servers that we recently joined to an Active Directory domain. The setup is: A local office network A virtual private cloud in Amazon An IPSec tunnel between the two networks A number of Windows 2008 R2 servers on both networks An AD domain (call it abc.net), with one domain controller in each network. The domain controllers are both new, fresh installs. Before we had the domain set up we had local accounts for the cloud computers which were used for RDP access. Our idea was to get all of the servers on to the domain so we could use domain logins instead of per-server local logins. Before the cloud servers were in the domain, RDP (from the office network or through a VPN to the cloud) worked great. After we joined the cloud servers to the domain, RDP from the office became very slow - a few minutes to log in, long frequent pauses when the interface is unresponsive, generally just a slow and frustrating experience. This is a problem regardless of whether a domain or local login is used for RDP. Oddly, when outside of the office network and connecting to the cloud directly with the VPN, RDP is still very responsive. Any idea why RDP from office to cloud is suddenly very slow after the cloud servers join the domain? What can I look at in our configuration to address this? Any help is greatly appreciated.

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  • Access denied to EFS encrypted files after PC joins domain

    - by mjmarsh
    I'm experiencing strange behavior with Windows Encrypted File System: I have a machine that is in workgroup mode (not joined to a domain) I encrypt an entire directory structure on the machine (basically a folder and subfolders with data files for my application). My application writes and reads files from the encrypted file hierarchy as a local Windows user (let's call the account 'SecureUser'). This works fine I then join the PC to a domain (Let's call it 'TEST') Afterwards, processes running as the local 'SecureUser' account can't read the files it wrote originally when it was off the domain (What is also strange is that the files are listed as "read only" now and I cannot unset this flag via Windows Explorer or the command line, even though it looks like it succeeds) I then 'un-join' the PC from the domain and everything works again Is there something about changing domain membership on a PC that changes the behavior of EFS so that previously encrypted files cannot be read, even by the originating user? Thanks in advance

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  • Advanced SQL query with lots of joins

    - by lund.mikkel
    Hey fellow programmers Okay, first let me say that this is a hard one. I know the presentation may be a little long. But I how you'll bare with me and help me through anyway :D So I'm developing on an advanced search for bicycles. I've got a lot of tables I need to join to find all, let's say, red and brown bikes. One bike may come in more then one color! I've made this query for now: SELECT DISTINCT p.products_id, #simple product id products_name, #product name products_attributes_id, #color id pov.products_options_values_name #color name FROM products p LEFT JOIN products_description pd ON p.products_id = pd.products_id INNER JOIN products_attributes pa ON pa.products_id = p.products_id LEFT JOIN products_options_values pov ON pov.products_options_values_id = pa.options_values_id LEFT JOIN products_options_search pos ON pov.products_options_values_id = pos.products_options_values_id WHERE pos.products_options_search_id = 4 #code for red OR pos.products_options_search_id = 5 #code for brown My first concern is the many joins. The Products table mainly holds product id and it's image and the Products Description table holds more descriptive info such as name (and product ID of course). I then have the Products Options Values table which holds all the colors and their IDs. Products Options Search is containing the color IDs along with a color group ID (products_options_search_id). Red has the color group code 4 (brown is 5). The products and colors have a many-to-many relationship managed inside Products Attributes. So my question is first of all: Is it okay to make so many joins? Is i hurting the performance? Second: If a bike comes in both red and brown, it'll show up twice even though I use SELECT DISTINCT. Think this is because of the INNER JOIN. Is this possible to avoid and do I have to remove the doubles in my PHP code? Third: Bikes can be double colored (i.e. black and blue). This means that there are two rows for that bike. One where it says the color is black and one where is says its blue. (See second question). But if I replace the OR in the WHERE clause it removes both rows, because none of them fulfill the conditions - only the product. What is the workaround for that? I really hope you will and can help me. I'm a little desperate right now :D Regards Mikkel Lund

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  • SQL Server CTE referred in self joins slow

    - by Kharlos Dominguez
    Hello, I have written a table-valued UDF that starts by a CTE to return a subset of the rows from a large table. There are several joins in the CTE. A couple of inner and one left join to other tables, which don't contain a lot of rows. The CTE has a where clause that returns the rows within a date range, in order to return only the rows needed. I'm then referencing this CTE in 4 self left joins, in order to build subtotals using different criterias. The query is quite complex but here is a simplified pseudo-version of it WITH DataCTE as ( SELECT [columns] FROM table INNER JOIN table2 ON [...] INNER JOIN table3 ON [...] LEFT JOIN table3 ON [...] ) SELECT [aggregates_columns of each subset] FROM DataCTE Main LEFT JOIN DataCTE BananasSubset ON [...] AND Product = 'Bananas' AND Quality = 100 LEFT JOIN DataCTE DamagedBananasSubset ON [...] AND Product = 'Bananas' AND Quality < 20 LEFT JOIN DataCTE MangosSubset ON [...] GROUP BY [ I have the feeling that SQL Server gets confused and calls the CTE for each self join, which seems confirmed by looking at the execution plan, although I confess not being an expert at reading those. I would have assumed SQL Server to be smart enough to only perform the data retrieval from the CTE only once, rather than do it several times. I have tried the same approach but rather than using a CTE to get the subset of the data, I used the same select query as in the CTE, but made it output to a temp table instead. The version referring the CTE version takes 40 seconds. The version referring the temp table takes between 1 and 2 seconds. Why isn't SQL Server smart enough to keep the CTE results in memory? I like CTEs, especially in this case as my UDF is a table-valued one, so it allowed me to keep everything in a single statement. To use a temp table, I would need to write a multi-statement table valued UDF, which I find a slightly less elegant solution. Did some of you had this kind of performance issues with CTE, and if so, how did you get them sorted? Thanks, Kharlos

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  • Using Joins vs Entity associations

    - by shivesh
    I am learning Entity framework and linq-to-entities. It's possible to get cross values from multiple tables using JOINS (join keyword) or using the navigation fields ( associations) in which case the framework knows how to reference the cross data. My question is what to use when?

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  • When to use JOINs

    - by waiwai933
    It seems to me that there are two scenarios in which to use JOINs: When data would otherwise be duplicated When data from one query would otherwise be used in another query Are these scenarios right? Are there any other scenarios in which to use JOIN?

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  • linq2sql and multiple joins

    - by zerkms
    is it possible to do multiple joins: from g in dataContext.Groups join ug in dataContext.UsersGroups on g.Id equals ug.GroupId join u in dataContext.Users on u. where ug.UserId == user.Id select GroupRepository.ToEntity(g); in the sample above all is fine until i press "." in the end of the 3rd line. there i expect to get intellisense and write u.Id == ug.UserId but it doesn't appear. and of course this code doesn't compile after. what did i wrong?

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  • Freebase Query with "JOINS"

    - by codemonkey
    ... Yeah, yeah, I know traditional joins don't exist. I actually like the freebase query methodology in theory, just having a little trouble getting it to actually work for me : ) Anyone have a dumb-simple example of getting Freebase data via MQL that pulls from two different "tables"? In particular, I'm trying to get automotive data... so for example, pulling fields from both /automotive/model_year and /automotive/trim_year. I've read the documentation (for hours actually). There's a distinct possibility that I'm looking right at such an example somewhere and just not seeing it because my OLTP brain just doesn't comprehend what it's seeing. * Note * ... that the two "types" I'm working with above are siblings, not parent/child. Does freebase even allow joining data between sibling nodes... I see examples of queries pulling from parent/child, but not from siblings I don't think (or I've overlooked them).

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  • How to have multiple tables with multiple joins

    - by williamsdb
    I have three tables that I need to join together and get a combination of results. I have tried using left/right joins but they don't give the desired results. For example: Table 1 - STAFF id name 1 John 2 Fred Table 2 - STAFFMOBILERIGHTS id staffid mobilerightsid rights --this table is empty-- Table 3 - MOBILERIGHTS id rightname 1 Login 2 View and what I need is this as the result... id name id staffid mobilerightsid rights id rightname 1 John null null null null 1 login 1 John null null null null 2 View 2 Fred null null null null 1 login 2 Fred null null null null 2 View I have tried the following : SELECT * FROM STAFFMOBILERIGHTS SMR RIGHT JOIN STAFF STA ON STA.STAFFID = SMR.STAFFID RIGHT JOIN MOBILERIGHTS MRI ON MRI.ID = SMR.MOBILERIGHTSID But this only returns two rows as follows: id name id staffid mobilerightsid rights id rightname null null null null null null 1 login null null null null null null 2 View Can what I am trying to achieve be done and if so how? Thanks

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  • SQL Server indexed view matching of views with joins not working

    - by usr
    Does anyone have experience of when SQL Servr 2008 R2 is able to automatically match indexed view (also known as materialized views) that contain joins to a query? for example the view select dbo.Orders.Date, dbo.OrderDetails.ProductID from dbo.OrderDetails join dbo.Orders on dbo.OrderDetails.OrderID = dbo.Orders.ID cannot be automatically matched to the same exact query. When I select directly from this view ith (noexpand) I actually get a much faster query plan that does a scan on the clustered index of the indexed view. Can I get SQL Server to do this matching automatically? I have quite a few queries and views... I am on enterprise edition of SQL Server 2008 R2.

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  • Most optimal order (of joins) for left join

    - by Ram
    I have 3 tables Table1 (with 1020690 records), Table2(with 289425 records), Table 3(with 83692 records).I have something like this SELECT * FROM Table1 T1 /* OK fine select * is bad when not all columns are needed, this is just an example*/ LEFT JOIN Table2 T2 ON T1.id=T2.id LEFT JOIN Table3 T3 ON T1.id=T3.id and a query like this SELECT * FROM Table1 T1 LEFT JOIN Table3 T3 ON T1.id=T3.id LEFT JOIN Table2 T2 ON T1.id=T2.id The query plan shows me that it uses 2 Merge Join for both the joins. For the first query, the first merge is with T1 and T2 and then with T3. For the second query, the first merge is with T1 and T3 and then with T2. Both these queries take about the same time(40 seconds approx.) or sometimes Query1 takes couple of seconds longer. So my question is, does the join order matter ?

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  • Speeding up inner joins between a large table and a small table

    - by Zaid
    This may be a silly question, but it may shed some light on how joins work internally. Let's say I have a large table L and a small table S (100K rows vs. 100 rows). Would there be any difference in terms of speed between the following two options?: OPTION 1: OPTION 2: --------- --------- SELECT * SELECT * FROM L INNER JOIN S FROM S INNER JOIN L ON L.id = S.id; ON L.id = S.id; Notice that the only difference is the order in which the tables are joined. I realize performance may vary between different SQL languages. If so, how would MySQL compare to Access?

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  • Question about joins and table with Millions of rows

    - by xRobot
    I have to create 2 tables: Magazine ( 10 millions of rows with these columns: id, title, genres, printing, price ) Author ( 180 millions of rows with these columns: id, name, magazine_id ) . Every author can write on ONLY ONE magazine and every magazine has more authors. So if I want to know all authors of Motors Magazine, I have to use this query: SELECT * FROM Author, Magazine WHERE ( Author.id = Magazine.id ) AND ( genres = 'Motors' ) The same applies to Printing and Price column. To avoid these joins with tables of millions of rows, I thought to use this tables: Magazine ( 10 millions of rows with this column: id, title, genres, printing, price ) Author ( 180 millions of rows with this column: id, name, magazine_id, genres, printing, price ) . and this query: SELECT * FROM Author WHERE genres = 'Motors' Is it a good approach ? I can use Postgresql or Mysql.

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