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• which is better, creating a materialized view or a new table?

  - by Carson

  I have some demanding mysql queries that are needed to grap same up-to-date datasets from 5-7 mysql tables. I am thinking of creating a table or materialized view to gather all demanding columns from other tables, so as to increase performance. If I create that table, I may need to do extra insert / update / delete operation each time other tables updated. if I create materialized view, I am worrying if the performance can be greatly improved. Because data from other tables are changing very frequently. Most likely, the view may need to be created first everytime before selecting it. Any ideas? e.g. how to cache? other extra measures I can do?

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• Mysql - multiple values and between

  - by realshadow

  Hey, I need to select 10 products and display them. Each product has 3 different prices. The select to get the prices looks like this: SELECT * FROM products_loans WHERE CODE IN('10X15/12', '10X15/Q10-10', '10X15/Q20-10') AND 550 BETWEEN PRICE_FROM AND PRICE_TO; Where 550 is the base price. Now this select returns 3 rows, but I want to modify it so it will return 30 results. I dont like the idea to execute 10 queries at once. I know I can easily achieve that with "OR", but I would like to ask if there is some other more elegant way to this. The select "should" look like this: SELECT * FROM products_loans WHERE KOD IN('10X15/12', '10X15/Q10-10', '10X15/Q20-10') AND (550, 325, 780) BETWEEN CENA_OD AND CENA_DO; Note that there is no "price" column or anything in the table which I could use to do a JOIN and I cant modify the table.

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• Getting the final value to this MySQL query...

  - by Jack W-H

  I've got my database set up with three tables - code, tags, and code_tags for tagging posts. This will be the SQL query processed when a post is submitted. Each tag is sliced up by PHP and individually inserted using these queries. INSERT IGNORE INTO tags (tag) VALUES ('$tags[1]'); SELECT tags.id FROM tags WHERE tag = '$tags[1]' ORDER BY id DESC LIMIT 1; INSERT INTO code_tags (code_id, tag_id) VALUES ($codeid, WHAT_GOES_HERE?) The WHAT_GOES_HERE? value at the end is what I need to know. It needs to be the ID of the tag that the second query fetched. How can I put that ID into the third query? I hope I explained that correctly. I'll rephrase if necessary.

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• Best performance approach to history mechanism?

  - by Royi Namir

  We are going to create History Mechanism for our changes in DB (DART in pic) via Triggers. we have 600 tables. Each record that will be changed - the trigger will insert the deleted one into XXX. regarding to the XXX : option 1 : clone each table in "Dart" DB and each table now will have a "sister table" e.g. : Table1 will have Table1_History problems : we will have 1200 tables programmer can do mistakes by working on wrong tables... option 2 : make a new DB (DART_2005 in pic) and the history tables will be there option 3 : use linked server which stores the Db which will contain the history tables. question : 1) which option gives the best performance ( I guess 3 is not - but is it 1 or 2 or same ?) 2) Does option 2 is acting like "linked server" ( in queries we will need to select from both DB's...) 3) What is the best practice approach ?

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• LINQ to Entity, joining on NOT IN tables

  - by SlackerCoder

  My brain seems to be mush right now! I am using LINQ to Entity, and I need to get some data from one table that does NOT exist in another table. For example: I need the groupID, groupname and groupnumber from TABLE A where they do not exist in TABLE B. The groupID will exist in TABLE B, along with other relevant information. The tables do not have any relationship. In SQL it would be quite simply (there is a more elegant and efficient solution, but I want to paint a picture of what I need) SELECT GroupID, GroupName, GroupNumber, FROM TableA WHERE GroupID NOT IN (SELECT GroupID FROM TableB) Is there an easy/elegant way to do this? Right now I have a bunch of queries hitting the db, then comparing, etc. It's pretty messy. Thanks.

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• Servicestack CorsFeature Global Options Handler Not Firing on Certain Routes;

  - by gizmoboy

  I've got a service setup using the CorsFeature, and am using the approach that mythz suggested in other answers, collected in a function used in the appHost file: private void ConfigureCors(Funq.Container container) { Plugins.Add(new CorsFeature(allowedOrigins: "*", allowedMethods: "GET, POST, PUT, DELETE, OPTIONS", allowedHeaders: "Content-Type, Authorization, Accept", allowCredentials: true)); PreRequestFilters.Add((httpReq, httpRes) => { //Handles Request and closes Responses after emitting global HTTP Headers if (httpReq.HttpMethod == "OPTIONS") { httpRes.EndRequest(); } }); } However, the pre-request filter is only firing on some of the service requests. One of the base entities we have in the service is a question entity, and there are custom routes defined as follows: [Route("/question")] [Route("/question/{ReviewQuestionId}", "GET,DELETE")] [Route("/question/{ReviewQuestionId}/{ReviewSectionId}", "GET")] Using POSTMAN to fire test queries (all using the OPTIONS verb), we can see that this will fire the pre-request filter: http://localhost/myservice/api/question/ But this will not: http://localhost/myservice/api/question/66 Presumably, this is because the second and third routes explicitly defined the verbs they accept, and OPTIONS isn't one of them. Is it really necessary to spell out OPTIONS in every defined route that restricts the verbs supported?

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• MongoDB map/reduce counts

  - by ibz

  The output from MongoDB's map/reduce includes something like 'counts': {'input': I, 'emit': E, 'output': O}. I thought I clearly understand what those mean, until I hit a weird case which I can't explain. According to my understanding, counts.input is the number of rows that match the condition (as specified in query). If so, how is it possible that the following two queries have different results? db.mycollection.find({MY_CONDITION}).count() db.mycollection.mapReduce(SOME_MAP, SOME_REDUCE, {'query': {MY_CONDITION}}).counts.input I thought the two should always give the same result, independent of the map and reduce functions, as long as the same condition is used.

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• Proper abstraction of the database tier in a 3 tier system?

  - by Earlz

  Hello, I am creating a 3 tier application. Basically it goes Client - (through optional server to be a thin-client) - Business Logic - Database Layer And basically making it so that there is never any skipping around. As such, I want for all of the SQL queries and such to be in the Database Layer. Well, now I'm a bit confused. I made a few static classes to start off the database tier but what should I do for the database connections? Should I just create a new database connection anytime I enter the Database Layer or would that be wasteful? Does Connection.Open() take time whenever you have a ConnectionPool? To me, it just feels wrong for the Business tier to have to pass in a IdbConnection object to the Database tier. It seems like the Database tier should handle all of that DB-specific code. What do you think? How can I do it the proper way while staying practical?

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• Database indexes - what should they be

  - by WebweaverD

  Most of my database tables have a clear unique index through which lookups are done 90% of the time but I am a bit unsure on this one - I have a table which keeps track of user rating totals for items in my database, I now want to add another table, to track individual ratings with an ip address column to make sure no one can rate something twice. Since I can see this becoming a big, high use table it is important to optimize it correctly. (MYSQL table) This table will have the following fields: rating_id(always - unique), item_id (always - not unique), user_id (optional - not unique), ip_address (always - not unique), rating_value(always - not unique), has_review(bool) Now I envisions 90% the queries going something like this: When a user rates something - select where item_id = x and ip_address = y, (if rows = 0) insert rating When in user account pages - select where ip_address = x or username = y Now none of the fields searched on are unique, can I still use them as indexes (for example item _id and ip_address), can I have two indexes and will this still improve performance over a non indexed table?

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• Getting user data from Active Directory using PL/SQL

  - by David Neale

  I had a discussion today regarding an Oracle procedure I wrote some time ago. I wanted to get 7500 user email addresses from Active Directory using PL/SQL. AD will return a maximum of 1000 rows and the LDAP provider used by Oracle will not support paging. Therefore, my solution was to filter on the last two characters of the sAMAccountName (*00,*01,*02...etc.). This results in 126 queries (100 for account names ending in digits, 26 for those ending in a letter...this was sufficient for my AD setup). The person I was speaking to (it was a job interview by the way) said he could have done it a better way, but he would not tell me what that method was. Could anybody hazard a guess at what this method was?

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• Has anyone used an object database with a large amount of data?

  - by Jon Kruger

  Object databases like MongoDB and db4o are getting lots of pub lately. Everyone that plays with them seems to love it. I'm guessing that they are dealing with about 640K of data in their sample apps. Has anyone tried to use an object database with a large amount of data (say, 50GB or more)? Are you able to still execute complex queries against it (like from a search screen)? How does it compare to your usual relational database of choice? I'm just curious. I want to take the object database plunge, but I need to know if it'll work on something more than a sample app.

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• Exploring search options for PHP

  - by Joshua

  I have innoDB table using numerous foreign keys, but we just want to look up some basic info out of it. I've done some research but still lost. 1) How can I tell if my host has Sphinx installed already? I don't see it as an option for table storage method (i.e. innodb, myisam). 2) Zend_Search_Lucene, responsive enough for AJAX functionality of millions of records? 3) Mirror my innoDB with a myisam? Make every innodb transaction end with a write to the myisam, then use 1:1 lookups? How would I do this automagically? This should make MyISAM ACID-compliant and free(er) from corruption no? 4) PostgreSQL fulltext queries don't even look like SQL to me wtf, I don't have time to learn a new SQL syntax I need noob options 5) ???????????????????? This is high volume site on a decently-equipped VPS Thanks very much for any ideas.

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• Custom keys for Google App Engine models (Python)

  - by Cameron

  First off, I'm relatively new to Google App Engine, so I'm probably doing something silly. Say I've got a model Foo: class Foo(db.Model): name = db.StringProperty() I want to use name as a unique key for every Foo object. How is this done? When I want to get a specific Foo object, I currently query the datastore for all Foo objects with the target unique name, but queries are slow (plus it's a pain to ensure that name is unique when each new Foo is created). There's got to be a better way to do this! Thanks.

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• Aggregate functions in ANSI SQL

  - by morpheous

  I want to use multiple aggregate functions in a query. All the examples i have seem on aggregate functions however, are trivial. Typically, they are of the form: SELECT field1,agg_func1, agg_func2 GROUP BY SOME_COLUMNS HAVING agg_func1 OP SOME_SCALAR Where: OP: is a boolean operator (e.g. <, = etc) SOME_SCALAR: is a scalar (i.e. a constant number) What I want to know is if it is possible to write (IN ANSI SQL) queries like: SELECT field1,agg_func1, agg_func2, agg_func3 GROUP BY SOME_COLUMNS HAVING (agg_func1 OP1 agg_func2) OP2 (agg_func2 OP3 agg_func3) Where: OP[N] are boolean operators or ANSI SQL clause operators like 'BETWEEN', 'LIKE', 'IN' etc. Also, assuming this is possible (I have not seen any documentation saying otherwise) are there any efficiency/performance considerations (i.e. penalties) when the HAVING clause consists of a boolean expression combining the output of the aggregate functions - instead of the normal comparison of the output of the aggregate with a constant number (e.g. min('salary') 100 ) - which is often used in the most banal examples involving aggregate functions?

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• Adding a MongoDB collection to Netbeans

  - by Saif Bechan

  In Netbeans I have an option to add my mysql databases to netbeans. This way I can easily browse and so small queries. Now I am working on a MongoDB project, and I want to know if it is possible to use the same functionality. I see that on the website of mongo there is a list of drivers, and I see that you can add drivers in netbeans. I do not know if the same thing, or if this can be used. I have tried google, but no luck. Anyone have an idea?

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• Overriding unique indexed values

  - by Yeti

  This is what I'm doing right now (name is UNIQUE): SELECT * FROM fruits WHERE name='apple'; Check if the query returned any result. If yes, don't do anything. If no, a new value has to be inserted: INSERT INTO fruits (name) VALUES ('apple'); Instead of the above is it ok to insert the value into the table without checking if it already exists? If the name already exists in the table, an error will be thrown and if it doesn't, a new record will be inserted. Right now I am having to insert 500 records in a for loop, which results in 1000 queries. Will it be ok to skip the "already-exists" check?

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• "lock request time out period exceeded" Error When Trying to See DB Hierarchies

  - by Lloyd Banks

  I have a DB that I can run basic queries (albeit much slower than normal) off of. When I try to see the hierarchy trees for tables, views, or procedures in SSMS Object Explorer, I get the "lock request time out period exceeded". My Report Server reports that run off of objects in this DB are no longer completing. Jobs associated with procedures stored on this DB also do not run. I tried using sp_who2 to find and kill all connections on the DB. This has not solved the problem. What is going on here? How can I resolve this?

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• Is this a valid benefit of using embedded SQL over stored procedures?

  - by George

  Here's an argument for SPs that I haven't heard. Flamers, be gentle with the down tick, Since there is overhead associated with each trip to the database server, I would suggest that a POSSIBLE reason for placing your SQL in SPs over embedded code is that you are more insulated to change without taking a performance hit. For example. Let's say you need to perform Query A that returns a scalar integer. Then, later, the requirements change and you decide that it the results of the scalar is x that then, and only then, you need to perform another query. If you performed the first query in a SP, you could easily check the result of the first query and conditionally execute the 2nd SQL in the same SP. How would you do this efficiently in embedded SQL w/o perform a separate query or an unnecessary query? Here's an example: --This SP may return 1 or two queries. SELECT @CustCount = COUNT(*) FROM CUSTOMER IF @CustCount 10 SELECT * FROM PRODUCT Can this/what is the best way to do this in embedded SQL?

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• How can I loop over a query for a specific number of times that may be greater than the result?

  - by JS

  I need to loop over a query exactly 12 times to complete rows in a form but rarely will the query return 12 rows. The cfquery endRow attribute doesn't force the loop to keep going if the result is < 12. If it did that would be ideal to use something like cfloop query="myQuery" endRow="12"... The 2 options that I have now are to skip the loop and write out all 12 rows but that results in a lot of duplicate code (there are 20 columns), or do a query of queries for each row which seems like a lot of wasted processing. Thanks for any ideas.

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• Help needed in AdventureWorks in a sql query.

  - by vaibhav

  I was just playing with adventureworks database in sqlserver. I got stuck in a query. I wanted to Select all titles from HumanResources.Employee which are either 'Male' or 'Female' but not both. i.e if title Accountant is Male and Female both I want to leave that title. I need only those titles where Gender is either Male or Female. I have done this till yet. select distinct(title) from humanresources.employee where gender='M' select distinct(title) from humanresources.employee where gender='F' Probably a join between these two queries, would work. But If you have any other solution, please let me know. It is not a homework. :) Thanks in advance.

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• MySQL query for initial filling of order column

  - by Sejanus

  Sorry for vague question title. I've got a table containing huge list of, say, products, belonging to different categories. There's a foreign key column indicating which category that particular product belongs to. I.e. in "bananas" row category might be 3 which indicates "fruits". Now I added additional column "order" which is for display order within that particular category. I need to do initial ordering. Since the list is big, I dont wanna change every row by hand. Is it possible to do with one or two queries? I dont care what initial order is as long as it starts with 1 and goes up. I cant do something like SET order = id because id counts from 1 up regardless of product category and order must start anew from 1 up for every different category.

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• ORM on iPhone. More simple than CoreData.

  - by Alexander Babaev

  The question is rather simple. I know that there is SQLite. There is Core Data also. But I need something in between. More object-oriented than SQLite API and simplier than Core Data. Main points are: I need access to stored entities only by id. No queries required. I need to store items of a single type, it means that I can use only one table if I choose SQLite. I want automatic object-relational conversion. Or object-storage if the storage is not relational. I can use object archiving, but I have to implement things (NSArchiver). But I want to write some kind of class and get persistence automatically. As it can be done with Hibernate/ActiveRecord/Core Data/etc. Thanks.

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• Multi join query returns to many results and improperly matched

  - by Woot4Moo

  I have the following minimal schema in Oracle: http://sqlfiddle.com/#!4/c1ed0/14 The queries I have run yield too many results and this query: select cat.*, status.*, source.* from cats cat, status status, source source Left OUTER JOIN source source2 on source2.sourceid = 1 Right OUTER JOIN status status2 on status2.isStray =0 order by cat.name will yield incorrect results. What I am expecting is a table that looks like the following however I cannot seem to come up with the correct SQL. NAME AGE LENGTH STATUSID CATSOURCE ISSTRAY SOURCEID CATID Adam 1 25 null null null 1 2 Bill 5 1 null null null null null Charles 7 5 null null null null null Steve 12 15 1 1 1 1 1 In plain English what I am looking for is to return all known cats + their associated cat source + their cat status while retaining null values. The only information I will have is the source that I am curious about. I also only want the cats that have a status of either STRAY or UNKNOWN (null)

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• Making OR/M loosely coupled and abstracted away from other layers.

  - by Genuine

  Hi all. In an n-tier architecture, the best place to put an object-relational mapping (OR/M) code is in the data access layer. For example, database queries and updates can be delegated to a tool like NHibernate. Yet, I'd like to keep all references to NHibernate within the data access layer and abstract dependencies away from the layers below or above it. That way, I can swap or plug in another OR/M tool (e.g. Entity Framework) or some approach (e.g. plain vanilla stored procedure calls, mock objects) without causing compile-time errors or a major overhaul of the entire application. Testability is an added bonus. Could someone please suggest a wrapper (i.e. an interface or base class) or approach that would keep OR/M loosely coupled and contained in 1 layer? Or point me to resources that would help? Thanks.

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• MySQL Cluster data nodes - slow SELECTs

  - by Boyan Georgiev

  Hi to all. First off, I'm new to MySQL Cluster. This is my pain: I've managed to setup a MySQL Cluster with two data nodes, two SQL nodes and one management server. Everything works pretty well, except the following: my data nodes are spread across an intranet link which incurs latency into communications between the data nodes. Apparently, due to MySQL Cluster's internal partitioning schemes, when my PHP application pulls data from the cluster via SELECT queries, parts of the data are pulled from both data nodes. This makes the page appear onscreen REALLY slowly. If I bring one data node offline, the data can only be pulled from that single remaining data node, and thus, the final result (HTML output) appears on the screen in a very timely fashion. So, my question is this: can the data nodes/cluster be told to pull data from partitions stored only on a particular data node?

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