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  • Does the order of the columns in a SELECT statement make a difference?

    - by Frank Computer
    This question was inspired by a previous question posted on SO, "Does the order of the WHERE clause make a differnece?". Would it improve a SELECT statement's performance if the the columns used in the WHERE section are placed at the begining of the SELECT statement? example: SELECT customer.id, transaction.id, transaction.efective_date, transaction.a, [...] FROM customer, transaction WHERE customer.id = transaction.id; I do know that limiting the list of columns to only the needed ones in a SELECT statement improves performance as opposed to using SELECT * because the current list is smaller.

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  • Query returning an ascending group number

    - by Dougman
    I have a query like below that has groups (COL1) and that group's values (COL2). select col1, col2 from (select 'A' col1, 1 col2 from dual union all select 'A' col1, 2 col2 from dual union all select 'B' col1, 1 col2 from dual union all select 'B' col1, 2 col2 from dual union all select 'C' col1, 1 col2 from dual union all select 'C' col1, 2 col2 from dual ) order by col1, col2; The output of this query looks like: COL1 COL2 ---- ---- A 1 A 2 B 1 B 2 C 1 C 2 What I need is a query that will return an ordered number increasing for each different group (COL1). It seems like there would be a simple way to accomplish this (maybe with analytics) but for some reason it is escaping me. GRPNUM COL1 COL2 ------ ---- ---- 1 A 1 1 A 2 2 B 1 2 B 2 3 C 1 3 C 2 I am running Oracle 10gR2.

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  • Database design

    - by Hadad
    Hello, I've a system, that have two types of users (Companies and individuals).all types have a shared set of properties but they differ in another. What is the best design merge all in one table that allows null for unmatched properties, or separate them in two tables related to a basic table with a one to one relationship. Thanks.

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  • Access database query locks ability to edit table?

    - by Sattvic
    I created a query in Microsoft Access like the one below: SELECT Deliverables.ID, Deliverables.Title, Deliverables.Summary, Deliverables.Header_Code, Deliverables.Header_Code.Value, Deliverables.Sort_order, Deliverables.Pillar, Deliverables.Pillar.Value, Deliverables.Misc_ID FROM Deliverables WHERE (((Deliverables.Pillar.Value)="Link Building")); But my problem is that this query locks my fields and I cannot make changes to the table using the query view. Any suggestions? I am using Microsoft Access 2007

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  • Oracle - truncating a global temporary table

    - by superdario
    I am processing large amounts of data in iterations, each and iteration processes around 10-50 000 records. Because of such large number of records, I am inserting them into a global temporary table first, and then process it. Usually, each iteration takes 5-10 seconds. Would it be wise to truncate the global temporary table after each iteration so that each iteration can start off with an empty table? There are around 5000 iterations.

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  • Cakephp Autoconvert find() fields?

    - by Razor Storm
    In cake php I can grab a model's fields by using the find() method. What if I wish to apply a transformation function to the fields? Is there a way to directly accomplish this task? Suppose I have a model called RaceTime with the fields racerId and timeMillis RaceTime +------------+ | Field | +------------+ | id | | racerId | | timeMillis | +------------+ timeMillis is an int specifying how long the race took in milliseconds. Obviously saying a race took 15651 milliseconds isn't very useful to a human reader, and I would wish to convert this to a human readable format. Is there a way to accomplish this directly in find()? Or is the only option to loop through the results after find() finishes?

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  • Centralizing / Abstracting MSSQL Data from Multiple Tables / Databases

    - by davemackey
    If one has a number of databases (due to separate application front-ends) that provide a complete picture - for example a CRM, accounting, and product database - what methods are available to centralize/abstract this data for easy reporting? Essentially, I'm wondering if there is a way to automatically pull data from multiple databases into a central repository that is continuously updated from the three databases and which can be used for reporting? I'm also open to alternative best practice suggestions?

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  • Redundancy in doing sum()

    - by Abhi
    table1 - id, time_stamp, value This table consists of 10 id's. Each id would be having a value for each hour in a day. So for 1 day, there would be 240 records in this table. table2 - id Table2 consists of a dynamically changing subset of id's present in table1. At a particular instance, the intention is to get sum(value) from table1, considering id's only in table2, grouping by each hour in that day, giving the summarized values a rank and repeating this each day. the query is at this stage: select time_stamp, sum(value), rank() over (partition by trunc(time_stamp) order by sum(value) desc) rn from table1 where exists (select t2.id from table2 t2 where id=t2.id) and time_stamp >= to_date('05/04/2010 00','dd/mm/yyyy hh24') and time_stamp <= to_date('25/04/2010 23','dd/mm/yyyy hh24') group by time_stamp order by time_stamp asc If the query is correct, can this be made more efficient, considering that, table1 will actually consist of thousand's of id's instead of 10 ? EDIT: I am using sum(value) 2 times in the query, which I am not able to get a workaround such that the sum() is done only once. Pls help on this

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  • Performance optimization for mssql: decrease stored procedures execution time or unload the server?

    - by tim
    Hello everybody! We have a web service which provides search over hotels. There is a problem with performance: a single request to the service takes around 5000 ms. Almost all of the time is spent in database by executing storing procedures. During the request our server (mssql2008) consumes ~90% of the processor time. When 2 requests are made in parallel the average time grows and is around 7000 ms. When number of request is increasing, the average time of response is increasing as well. We have 20-30 requests per minute. Which kind of optimization is the best in this case having in mind that the goal is to provide stable response time for the service: 1) Try to decrease the stored procedures execution time 2) Try to find the way how to unload the server It is interesting to hear from people who deal with booking sites. Thanks!

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  • One on One table relation - is it harmful to keep relation in both tables?

    - by EBAGHAKI
    I have 2 tables that their rows have one on one relation.. For you to understand the situation, suppose there is one table with user informations and there is another table that contains a very specific informations and each user can only link to one these specific kind of informations ( suppose second table as characters ) And that character can only assign to the user who grabs it, Is it against the rules of designing clean databases to hold the relation key in both tables? User Table: user_id, name, age, character_id Character Table: character_id, shape, user_id I have to do it for performance, how do you think about it?

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  • is Payment table needed when you have an invoice table like this?

    - by EBAGHAKI
    this is my invoice table: Invoice Table: invoice_id creation_date due_date payment_date status enum('not paid','paid','expired') user_id total_price I wonder if it's Useful to have a payment table in order to record user payments for invoices. payment table can be like this: payment_id payment_date invoice_id price_paid status enum('successful', 'not successful')

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  • Insert into select and update in single query

    - by Ossi
    I have 4 tables: tempTBL, linksTBL and categoryTBL, extra on my tempTBL I have: ID, name, url, cat, isinserted columns on my linksTBL I have: ID, name, alias columns on my categoryTBL I have: cl_id, link_id,cat_id on my extraTBL I have: id, link_id, value How do I do a single query to select from tempTBL all items where isinsrted = 0 then insert them to linksTBL and for each record inserted, pickup ID (which is primary) and then insert that ID to categoryTBL with cat_id = 88. after that insert extraTBL ID for link_id and url for value. I know this is so confusing, put I'll post this anyhow... This is what I have so far: INSERT IGNORE INTO linksTBL (link_id,link_name,alias) VALUES(NULL,'tex2','hello'); # generate ID by inserting NULL INSERT INTO categoryTBL (link_id,cat_id) VALUES(LAST_INSERT_ID(),'88'); # use ID in second table I would like to add here somewhere that it only selects items where isinserted = 0 and iserts those records, and onse inserted, will change isinserted to 1, so when next time it runs, it will not add them again.

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  • Combine First, Middle Initial, Last name and Suffix in T-SQL (No extra spaces)

    - by Paul
    I'm trying not to reinvent the wheel here...I have these four fields [tbl_Contacts].[FirstName], [tbl_Contacts].[MiddleInitial], [tbl_Contacts].[LastName], [tbl_Contacts].[Suffix] And I want to create a FullName field in a view, but I can't have extra spaces if fields are blank...So I can't do FirstName + ' ' + MiddleInitial + ' ' + LastName + ' ' + Suffix...Because if there is no middle initial or suffix I'd have 2 extra spaces in the field. I think I need a Case statement, but I thought someone would have a handy method for this...Also, the middleinitial and suffix may be null.

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  • How effecient is a details table?

    - by Jeffrey Lott
    At my job, we have pseudo-standard of creating one table to hold the "standard" information for an entity, and a second table, named like 'TableNameDetails', which holds optional data elements. On average, for every row in the main table will have about 8-10 detail rows in it. My question is: What kind of performance impacts does this have over adding these details as additional nullable columns on the main table?

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  • SQL query construction - separate data in a column into two columns

    - by Tommy
    I have a column that contains links. The problem is that the titles of the links are in the same column, so it looks like this: linktitle|-|linkurl I want link title and linkurl in separate columns. I've created a new column for the urls, so I'm looking for a way to extract them and update the linkurl column with them. Is there any clever way to construct a query that does this?

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