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  • SQL Server - how to determine if indexes aren't being used?

    - by rwmnau
    I have a high-demand transactional database that I think is over-indexed. Originally, it didn't have any indexes at all, so adding some for common processes made a huge difference. However, over time, we've created indexes to speed up individual queries, and some of the most popular tables have 10-15 different indexes on them, and in some cases, the indexes are only slightly different from each other, or are the same columns in a different order. Is there a straightforward way to watch database activity and tell if any indexes are not hit anymore, or what their usage percentage is? I'm concerned that indexes were created to speed up either a single daily/weekly query, or even a query that's not being run anymore, but the index still has to be kept up to date every time the data changes. In the case of the high-traffic tables, that's a dozen times/second, and I want to eliminate indexes that are weighing down data updates while providing only marginal improvement.

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  • How to document an existing small web site (web application), inside and out?

    - by Ricket
    We have a "web application" which has been developed over the past 7 months. The problem is, it was not really documented. The requirements consisted of a small bulleted list from the initial meeting 7 months ago (it's more of a "goals" statement than software requirements). It has collected a number of features which stemmed from small verbal or chat discussions. The developer is leaving very soon. He wrote the entire thing himself and he knows all of the quirks and underlying rules to each page, but nobody else really knows much more than the user interface side of it; which of course is the easy part, as it's made to be intuitive to the user. But if someone needs to repair or add a feature to it, the entire thing is a black box. The code has some minimal comments, and of course the good thing about web applications is that the address bar points you in the right direction towards fixing a problem or upgrading a page. But how should the developer go about documenting this web application? He is a bit lost as far as where to begin. As developers, how do you completely document your web applications for other developers, maintainers, and administrative-level users? What approach do you use, where do you start, do you have a template? An idea of magnitude: it uses PHP, MySQL and jQuery. It has about 20-30 main (frontend) files, along with about 15 included files and a couple folders of some assets. So overall it's a pretty small application. It interfaces with 7 MySQL tables, each one well-named, so I think the database end is pretty self-explanatory. There is a config.inc.php file with definitions of consts like the MySQL user details, some from/to emails, and URLs which PHP uses to insert into emails and pages (relative and absolute paths, basiecally). There is some AJAX via jQuery. Please comment if there is any other information that would help you help me and I will be glad to edit it in.

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  • Write a SQL Query to replace values and include all the Dates.

    - by VJ
    Well I have this - Table DimDate- Date Table Employee- Id,Name,Points,Date Now the Employee table has points for everyday unless they did not come...so the Date does not have all the Dates entries... I mean for e.g in a week he did not come for 2 days the Employee table has only 5 rows...so I have this dimdate table which has all the dates till 2050 which I want to join with and add Zeros for the dates he does not have points. So I have written this query but does not work - Select E.EmployeeId,D.Date,isNull(E.Points,0) from DimDate D left join Employee E on D.Date between '01-01-2009'and '06-01-2009' where E.EmployeeId=1 The above query give multiple dates and I tried group by on Date but does not work.

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  • Is "campaign_$" a bad name for a SQL column?

    - by Summer
    PostgreSQL has allowed me to name a column "campaign_$". I like the name because it's short and to the point, and other potential names like "campaign_receipts" seem longer and less clear. BUT, I wonder if I'll eventually regret putting a $ symbol in a column name, either in PHP or in some other distant part of the architecture. Should I just stick to letters and underscores? Thanks!

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  • How many SQL queries per HTTP request is optimal?

    - by Chris Kooken
    I know the answer to this question for the most part is "It Depends", however I wanted to see if anyone had some pointers. We execute queries each request in ASP.NET MVC. Each request we need to get user rights information, and Various data for the Views that we are displaying. How many is too much, I know I should be conscious to the number of queries i am executing. I would assume if they are small queries and optimized out, half-a-dozen should be okay? Am I right? What do you think?

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  • SQL Server 2003: how can I assign a name to the SUM column ?

    - by Patrick
    hi, how can I assign a column name to the SUM column ? i.e. select OwnerUserId, SUM(PostScore) INTO Experts from ... I get this error: An object or column name is missing or empty. For SELECT INTO statements, verify each column has a name. For other statements, look for empty alias names. Aliases defined as "" or [] are not allowed. Change the alias to a valid name. I guess because the column containing the results of SUM has not name. thanks

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  • Why would SQL be very slow when doing updates?

    - by ooo
    Suddenly doing updates into a few tables have gotten 10 times slower than they used to be. What are some good recommendations to determine root cause and optimization? Could it be that indexing certain columns are causing updates to be slow? Any other recommendations? I guess more important than guesses would be help on the process of identifying the root cause or metrics around performance. Is there anything in Fluent NHibernate that you can use to help identify the root cause of performance issues?

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  • SQL grouping query question; evaluating a group of rows based on the value of one field.

    - by user324575
    I've got table vendorparts that lists all my parts and their vendor(s). Parts with multiple vendors have multiple records in this table. I'm trying to write a query that only returns the partid, and vendor of parts that do not have a default vendor assigned. Partid Vendor Defaultflag 1 A 1 2 B 0 2 C 0 3 D 0 3 E 0 3 F 1 4 G 0 I would like to return the following: Partid Vendor 2 A 2 B 4 G I'm obviously having issues with partid 3 and getting the query to see it as having a default vendor assigned.

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  • How to query by recent date and value in SQL?

    - by wsb3383
    I have a table with three columns: patient_id, obs_date, and weight_val. patient_id stores patient identification #, weight_val stores a weight value, and obs_date stores the date when the weight reading was taken. So, a patient can have many different weight readings at different dates. How do you write a query for: select all patients whose last weight reading is 120?

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  • [MS Access 2003 SQL] Switch is causing #error, why and how can I fix it...

    - by Chris
    I have 3 fields in my table: start, end (dates) and length (number, might be blank). My Aim is to calculate an end date using start and length where end doesn't exist... I have: SELECT Switch((g.length<>0) And IsDate(g.end),DateAdd("m",g.length,g.start)) AS field FROM table g If there is no start, end or length, Access displays blank - this is fine. If there is no end, but start and length are ok, the calculated date is shown - again fine. BUT If there is no end, or length, but a start exists, access displays #Error I don't understand why, and can't fix it, please help!

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  • which sql query is more efficient: select count(*) or select ... where key>value?

    - by davka
    I need to periodically update a local cache with new additions to some DB table. The table rows contain an auto-increment sequential number (SN) field. The cache keeps this number too, so basically I just need to fetch all rows with SN larger than the highest I already have. SELECT * FROM table where SN > <max_cached_SN> However, the majority of the attempts will bring no data (I just need to make sure that I have an absolutely up-to-date local copy). So I wander if this will be more efficient: count = SELECT count(*) from table; if (count > <cache_size>) // fetch new rows as above I suppose that selecting by an indexed numeric field is quite efficient, so I wander whether using count has benefit. On the other hand, this test/update will be done quite frequently and by many clients, so there is a motivation to optimize it.

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  • How do I remove database name from SQL Server generated script?

    - by bucha
    Anytime I use 'script table as' - 'Insert To' (or other command), the script generated automatically places the database name in the script. Such as: INSERT INTO [DatabaseName].[dbo].[tblToBeInserted] ... While not a huge problem to just delete it, it has slipped by a few times and the script breaks if run on a different server with a different database name but has the same schema. (Such as running on [DatabaseName.Test]) Is there an option I can change, or can I modify the output in any way to remove this?

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  • Can you define values in a SQL statement that you can join/union, but are not stored in a table outs

    - by Mervyn
    I'm trying to create a query and need to join against something that I can define values in without creating a table. I'll attempt to describe what I'm trying to do: table1 is joined on field a with table2 (titles for FK in table 1) - Table1 has values outside of what exists in table2 - I want to add an additional 'table' to be unioned with table2 and then joined with table 1 Thanks

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  • SQL query to get lowest 2 values of a counted query selection (using db2)?

    - by jNoob
    Hi, Imagine I already have a query that returns the following: Col1 | Col2 ------------ A | 2 B | 3 C | 3 D | 4 E | 8 ... Say I used something like this: select Col1, count ( * ) as Col2 \ from ... where ... order by Col2 \ group by Col1 \ So now, all I want to select are (Col1, Col2) such that it returns the selections (a, b) and (c, d) where (b >= all (Col2)) and (d >= ((all (Col2)) - a)). So for the above example, it would return {(A, 2), (B, 3), (C, 3)}. How do I go about doing this? Any help would be highly appreciated. Thanks.

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  • [Linq to sql] query result what should i use Count() or Any()...

    - by Pandiya Chendur
    I am checking login of a user by this repository method, public bool getLoginStatus(string emailId, string password) { var query = from r in taxidb.Registrations where (r.EmailId == emailId && r.Password==password) select r; if (query.Count() != 0) { return true; } return false; } I saw in one of the previous questions !query.Any() would be faster... Which should i use? Any suggestion....

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