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  • What should every developer know about databases?

    - by Aaronaught
    Whether we like it or not, many if not most of us developers either regularly work with databases or may have to work with one someday. And considering the amount of misuse and abuse in the wild, and the volume of database-related questions that come up every day, it's fair to say that there are certain concepts that developers should know - even if they don't design or work with databases today. So: What are the important concepts that developers and other software professionals ought to know about databases? Guidelines for Responses: Keep your list short. One concept per answer is best. Be specific. "Data modelling" may be an important skill, but what does that mean precisely? Explain your rationale. Why is your concept important? Don't just say "use indexes." Don't fall into "best practices." Convince your audience to go learn more. Upvote answers you agree with. Read other people's answers first. One high-ranked answer is a more effective statement than two low-ranked ones. If you have more to add, either add a comment or reference the original. Don't downvote something just because it doesn't apply to you personally. We all work in different domains. The objective here is to provide direction for database novices to gain a well-founded, well-rounded understanding of database design and database-driven development, not to compete for the title of most-important.

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  • database design suggestion needed

    - by JMSA
    I need to design a table for daily sales of pharmaceutical products. There are hundreds of types of products available {Name, code}. Thousands of sales-persons are employed to sell those products{name, code}. They collect products from different depots{name, code}. They work in different Areas - Zones - Markets - Outlets, etc. {All have names and codes} Each product has various types of prices {Production Price, Trade Price, Business Price, Discount Price, etc.}. And, sales-persons are free to choose from those combination to estimate the sales price. The problem is, daily sales requires huge amount of data-entry. Within couple of years there may be gigabytes of data (if not terabytes). If I need to show daily, weekly, monthly, quarterly and yearly sales reports there will be various types of sql queries I shall need. This is my initial design: Product {ID, Code, Name, IsActive} ProductXYZPriceHistory {ID, ProductID, Date, EffectDate, Price, IsCurrent} SalesPerson {ID, Code, Name, JoinDate, and so on..., IsActive} SalesPersonSalesAraeaHistory {ID, SalesPersonID, SalesAreaID, IsCurrent} Depot {ID, Code, Name, IsActive} Outlet {ID, Code, Name, AreaID, IsActive} AreaHierarchy {ID, Code, Name, PrentID, AreaLevel, IsActive} DailySales {ID, ProductID, SalesPersonID, OutletID, Date, PriceID, SalesPrice, Discount, etc...} Now, apart from indexing, how can I normalize my DailySales table to have a fine grained design that I shall not need to change for years to come? Please show me a sample design of only the DailySales data-entry table (from which all types of reports would be queried) on the basis of above information. I don't need a detailed design advice. I just need an advice regarding only the DailySales table. Is there any way to break this particular table to achieve granularity?

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  • Advantage Database Server ORDER BY behaviour

    - by ie
    I'm using ADS v10 beta. I'm trying to numerate ordered resultset. 1) ORDER BY in nested queries. I need to use nested SELECT for some calculations: SELECT Name, Value, ROWNUM() FROM (SELECT * FROM MainTable WHERE Value > 0 ORDER BY Value) a And I'm getting Expected lexical element not found: ) There was a problem parsing the table names after the FROM keyword in your SELECT statement. Everything is working well when the ORDER BY is removed. Although, I found the sample in the Help, it looks like my query (more complex, indeed): SELECT * FROM (SELECT TOP 10 empid, fullname FROM branch1 ORDER BY empid) a UNION SELECT empid, fullname FROM branch2 ORDER BY empid 2) ORDER BY + ROWNUM(). I used the nested query in the example above, to numerate ordered rows. Is there are any chance to avoid nested query? In the SQL Server I can do something like this: SELECT Name, Value, ROW_NUMBER() OVER(ORDER BY Value) FROM MainTable WHERE Value > 1 ORDER BY Value Please advice. Thanks.

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  • SQL SERVER – FIX : ERROR : 4214 BACKUP LOG cannot be performed because there is no current database

    - by pinaldave
    I recently got following email from one of the reader. Hi Pinal, Even thought my database is in full recovery mode when I try to take log backup I am getting following error. BACKUP LOG cannot be performed because there is no current database backup. (Microsoft.SqlServer.Smo) How to fix it? Thanks, [name and email removed as requested] Solution / Fix: This error can happen when you have never taken full backup of your database and you try to attempt to take backup of the log only. Take full backup once and attempt to take log back up. If the name of your database is MyTestDB follow procedure as following. BACKUP DATABASE [MyTestDB] TO DISK = N'C:\MyTestDB.bak' GO BACKUP LOG [MyTestDB] TO DISK = N'C:\MyTestDB.bak' GO Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Backup and Restore, SQL Error Messages, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL Log

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  • CakePHP Missing Database Table Error

    - by BRADINO
    I am baking a new project management application at work and added a couple new tables to the database today. When I went into the console to bake the new models, they were not in the list... php /path/cake/console/cake.php bake all -app /path/app/ So I manually typed in the model name and I got a missing database table for model error. I checked and double-checked and the database table was named properly. Turns out that some files inside the /app/tmp/cache/ folder were causing Cake not to recognize that I had added new tables to my database. Once I deleted the cache files cake instantly recognized my new database tables and I was baking away! rm -Rf /path/app/tmp/cache/cake*

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  • PHP OCI8 and Oracle 11g DRCP Connection Pooling in Pictures

    - by christopher.jones
    Here is a screen shot from a PHP OCI8 connection pooling demo that I like to run. It graphically shows how little database host memory is needed when using DRCP connection pooling with Oracle Database 11g. Migrating to DRCP can be as simple as starting the pool and changing the connection string in your PHP application. The script that generated the data for this graph was a simple "Parts" query application being run under various simulated user loads. I was running the database on a small Oracle Linux server with just 2G of memory. I used PHP OCI8 1.4. Apache is in pre-fork mode, as needed for PHP. Each graph has time on the horizontal access in arbitrary 'tick' time units. Click the image to see it full sized. Pooled connections Beginning with the top left graph, At tick time 65 I used Apache's 'ab' tool to start 100 concurrent 'users' running the application. These users connected to the database using DRCP: $c = oci_pconnect('phpdemo', 'welcome', 'myhost/orcl:pooled'); A second hundred DRCP users were added to the system at tick 80 and a final hundred users added at tick 100. At about tick 110 I stopped the test and restarted Apache. This closed all the connections. The bottom left graph shows the number of statements being executed by the database per second, with some spikes for background database activity and some variability for this small test. Each extra batch of users adds another 'step' of load to the system. Looking at the top right Server Process graph shows the database server processes doing the query work for each web user. As user load is added, the DRCP server pool increases (in green). The pool is initially at its default size 4 and quickly ramps up to about (I'm guessing) 35. At tick time 100 the pool increases to my configured maximum of 40 processes. Those 40 processes are doing the query work for all 300 web users. When I stopped the test at tick 110, the pooled processes remained open waiting for more users to connect. If I had left the test quiet for the DRCP 'inactivity_timeout' period (300 seconds by default), the pool would have shrunk back to 4 processes. Looking at the bottom right, you can see the amount of memory being consumed by the database. During the initial quiet period about 500M of memory was in use. The absolute number is just an indication of my particular DB configuration. As the number of pooled processes increases, each process needs more memory. You can see the shape of the memory graph echoes the Server Process graph above it. Each of the 300 web users will also need a few kilobytes but this is almost too small to see on the graph. Non-pooled connections Compare the DRCP case with using 'dedicated server' processes. At tick 140 I started 100 web users who did not use pooled connections: $c = oci_pconnect('phpdemo', 'welcome', 'myhost/orcl'); This connection string change is the only difference between the two tests. At ticks 155 and 165 I started two more batches of 100 simulated users each. At about tick 195 I stopped the user load but left Apache running. Apache then gradually returned to its quiescent state, killing idle httpd processes and producing the downward slope at the right of the graphs as the persistent database connection in each Apache process was closed. The Executions per Second graph on the bottom left shows the same step increases as for the earlier DRCP case. The database is handling this load. But look at the number of Server processes on the top right graph. There is now a one-to-one correspondence between Apache/PHP processes and DB server processes. Each PHP processes has one DB server processes dedicated to it. Hence the term 'dedicated server'. The memory required on the database is proportional to all those database server processes started. Almost all my system's memory was consumed. I doubt it would have coped with any more user load. Summary Oracle Database 11g DRCP connection pooling significantly reduces database host memory requirements allow more system memory to be allocated for the SGA and allowing the system to scale to handled thousands of concurrent PHP users. Even for small systems, using DRCP allows more web users to be active. More information about PHP and DRCP can be found in the PHP Scalability and High Availability chapter of The Underground PHP and Oracle Manual.

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  • Apache cannot find mysql database modules

    - by user809857
    I've created a simple django project and setup a mysql database. My simple project just creates an entry on the database. The project works fine when I use the built in development server provided by django (runserver) and it works well. But when I deployed the project on Apache and mod_Wsgi (Ubuntu server), django could not find 'books', which is in this case my table in the database. The mysql database that I use in runserver and apache are just the same. I also did rebuild the database using sqlall,validate and syncdb of django but still i get the error. What could be wrong with what I'm doing? Thanks

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  • Apache cannot find mysql database modules

    - by user809857
    I've created a simple django project and setup a mysql database. My simple project just creates an entry on the database. The project works fine when I use the built in development server provided by django (runserver) and it works well. But when I deployed the project on Apache and mod_Wsgi (Ubuntu server), django could not find 'books', which is in this case my table in the database. The mysql database that I use in runserver and apache are just the same. I also did rebuild the database using sqlall,validate and syncdb of django but still i get the error. What could be wrong with what I'm doing? Thanks

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  • Oracle Database 12c

    - by jgelhaus
    What's your pain? Cost of IT and downtime, Complexity of IT, Poor database application performance? All of the above and more? These are real challenges caused by today's demands on data centers and their IT teams.  Oracle Database 12c provides a breakthrough architecture that makes it easy to deploy and manage databases in the cloud. Oracle partners will leverage Database 12c innovation to provide additional options for Oracle customer success and ROI. Download Oracle Database 12c and plug into the cloud! Join us for our July 10th webcast to learn about this database breakthrough.

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  • Lower Your Application Infrastructure Costs w/Oracle Database 11g

    - by john.brust
    Oracle Database 11g is designed to support enterprise applications, including Oracle E-Business Suite, Oracle PeopleSoft, and Oracle Siebel. And every Oracle customer can benefit from the performance, reliability, and security that Oracle Database 11g brings to these applications. Plus, Oracle Database 11g, helps you drive down your IT infrastructure costs. Join us next Friday for a webcast conversation with database expert Mark Townsend, Vice President of Oracle's Server Technology Division, to learn how you can benefit from running your applications on Oracle Database 11g. At the end of the presentation, we'll open up for live Q&A for approximately 30 minutes. Register now for our Friday, April 23rd, 2010 9:30am PT | 12:30pm ET live webcast.

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  • How should calculations be handled in a document database

    - by Morten
    Ok, so I have a program that basically logs errors into a nosql database. Right now there is just a single model for an error and its stored as a document in the nosql database. Basically I want to summarize across different errors and produce a summary of the "types" of errors that occured. Traditionally in a SQL database the this normalization would work with groupings, sums and averages but in a NoSQL database I assume I need to use mapreduce. My current model seems unfit for the task, how should I change the way I store "models" in order to make statistical analysis easy? Would a NoSQL database even be the right tool for this type of problem? I'm storing things in Google AppEngine's BigTable, so there are some limitations to think of as well.

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  • Podcast: Dell Perot Systems Relies on Oracle In-Memory Database Cache

    - by john.brust
    Recently we spoke with Bill Binko, Technology Consultant at Dell Perot Systems, about a high volume web-based content delivery system they implemented for a client with Oracle In-Memory Database Cache. Their client needed to respond to ~1 billion hits (web requests) per day, but hadn't been able to support this load. Oracle In-Memory Database Cache allowed for multiple & complicated queries to take place without ever hitting the disk...providing sub-millisecond response time and ability to manage much higher high volumes of data. Old System: Old SQL Server Database, over 300 servers, difficult to maintain. New System: One Oracle Database 11g instance, multiple Oracle RAC nodes, backed up by Oracle Data Guard, and Oracle In-Memory Database Cache to cut query response times by 10x. Listen to the podcast.

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  • 9/18 Live Webcast: Three Compelling Reasons to Upgrade to Oracle Database 11g

    - by jgelhaus
    Webcast: Three Compelling Reasons to Upgrade to Oracle Database 11g Date: Tuesday, September 18, 2012 Time: 10 a.m. PT/1 p.m. ET If you or your organization is still working with Oracle Database 10g or an even older version, now is the time to upgrade. Oracle Database 11g offers a wide variety of advantages to enhance your operation. Join us for this live Webcast and learn about what you’re missing: the business, operational, and technical benefits. With Oracle Database 11g, you can: Upgrade with zero downtime Improve application performance and database security Reduce the amount of storage required Save time and money Register today here

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  • Building ASP.NET Web Forms to Use a MySQL Database

    The MySQL database is the best open source database which means it can be used for free without obtaining or paying for a license. In ASP.NET 3.5 hosting there are some hosting packages that let you use the MySQL database because it can be a cheaper hosting alternative when compared to using the MS SQL database. However things can be a bit complicated when querying a MySQL database in an ASP.NET environment.... Advance Your IT Career Online IT Degree Programs. Advance Your IT Career While You Work. Search now.

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  • Eliminating Downtime During Database Upgrades: A Customer Case Study

    - by irem.radzik(at)oracle.com
    Planned outages, such as database, OS, hardware upgrades and migrations, are a fact of life. Even though they are "planned" and many of them are performed during "off business hours", they can still interrupt operations-- especially for global operations and online businesses. For this reason many IT organizations postpone these critical infrastructure improvement projects, which in turn result in delays in advancing business operations. This week, on Thursday January 13th, we will host a free webcast on this topic, and will feature Oracle GoldenGate's customer Atmos Energy. Atmos Energy implemented Oracle GoldenGate for eliminating downtime during their database upgrade from Oracle Database 8.1.7 to Oracle Database 11.1.0.7. Jos Francis, Lead DBA for Atmos, and Ronald Nedd, Sr. DBA for Atmos, will be presenting their database upgrade project and their solution architecture. Join us at this live webcast and hear from our customer and product management how to eliminate planned outages with Oracle GoldenGate's real-time, heterogeneous data replication capabilities.

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  • Webcast Series: Accelerate Business-Critical Database Deployments with Oracle Optimized Solutions

    - by ferhat
    Join us for this two-part Webcast series and learn how to safely consolidate business-critical databases and deliver quantifiable benefits to the business: Save up to 75% in operational and acquisition costs Save millions of dollars consolidating legacy infrastructure Leverage best practices from thousands of customer environments Increase end user productivity with 75% faster time to operations and 4x faster throughput   The Oracle Optimized Solution for Oracle Database  provides extensive guidelines for architecting and deploying complete database solutions that deliver superior performance and availability while minimizing cost and risk. Oracle’s world-class engineering teams work together to define these optimal architectures using Oracle's powerful SPARC M-Series and SPARC T-Series servers together with Oracle Solaris and Oracle's SAN, NAS, and flash-based storage to run the industry-leading Oracle Database. Quite simply, the Oracle Optimized Solution for Oracle Database makes it easier for you to deliver and manage business critical database environments that are fast, secure and cost-effective. Available On-Demand PART 1: Why Architecture Matters When Deploying Business-Critical Databases PART 2: How To Consolidate Databases Using Oracle Optimized Solutions   Presented by: Lawrence McIntosh, Principal Enterprise Architect, Oracle Optimized Solutions Ken Kutzer, Principal Product Manager, Infrastructure Solutions, Oracle  

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  • I want a trivial example of where MongoDB can scale but a relational database will have trouble

    - by Ryan Weir
    I'm just learning to use MongoDB, and when discussing with other programmers would like a quick example of why NoSQL can be a good choice compared to a traditional RDBMS - however the scenarios I come up with and can find online seem pretty contrived. E.g. a blog with lots of traffic could be represented relationally, but will require some performance tuning and joins across tables (assuming full denormalization is being used). Whereas MongoDB would allow direct retrieval from one collection to the same effect. But the response I'm getting from other programmers is "why not just keep it relational and then add some trivial caching later?" Does anybody have a less contrived example where MongoDB will really shine and a relational db will fall over much quicker? The smaller the project/system the better, because it leaves less room for disagreement. Something along the lines of the complexity of the blog example would be really useful. Thanks.

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  • Should custom data elements be stored as XML or database entries?

    - by meteorainer
    There are a ton of questions like this, but they are mostly very generalized, so I'd like to get some views on my specific usage. General: I'm building a new project on my own in Django. It's focus will be on small businesses. I'd like to make it somewhat customizble for my clients so they can add to their customer/invoice/employee/whatever items. My models would reflect boilerplate items that all ModelX might have. For example: first name last name email address ... Then my user's would be able to add fields for whatever data they might like. I'm still in design phase and am building this myself, so I've got some options. Working on... Right now the 'extra items' models have a FK to the generic model (Customer and CustomerDataPoints for example). All values in the extra data points are stored as char and will be coerced/parced into their actual format at view building. In this build the user could theoretically add whatever values they want, group them in sets and generally access them at will from the views relavent to that model. Pros: Low storage overhead, very extensible, searchable Cons: More sql joins My other option is to use some type of markup, or key-value pairing stored directly onto the boilerplate models. This coul essentially just be any low-overhead method weather XML or literal strings. The view and form generated from the stored data would be taking control of validation and reoganizing on updates. Then it would just dump the data back in as a char/blob/whatever. Something like: <datapoint type='char' value='something' required='true' /> <datapoint type='date' value='01/01/2001' required='false' /> ... Pros: No joins needed, Updates for validation and views are decoupled from data Cons: Much higher storage overhead, limited capacity to search on extra content So my question is: If you didn't live in the contraints impose by your company what method would you use? Why? What benefits or pitfalls do you see down the road for me as a small business trying to help other small businesses? Just to clarify, I am not asking about custom UI elements, those I can handle with forms and template snippets. I'm asking primarily about data storage and retreival of non standardized data relative to a boilerplate model.

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  • SQL Server architecture - they want to move my database to new instance...Why?

    - by O'MALLEY
    Our current production database environment contains about 10 similarily managed databases. Our agency has just purchased and is installing new blade chasses and wants to move my database to a new instance (leaving the other 9 on another). This decision is being driven by one of our IT staff, not a DBA. I am a project manager, not a DBA but I know enough to not necesarrily have a good feeling about this decision and I am urging our IT department to make a sound decision based on what is best for the database. Our IT department has stated that it is not good to have all our eggs in one basket, and has also stated that my database contains "regulatory data" so it should be on its own instance. A couple of truths: - None of the databases on the current instance are OLTP databases nor are any of them data warehouses - My database currently has joins/views to a couple of the other databases in the production environment So my questions are as follows: Am I wrong to disregard a statement about eggs in baskets? (hello, this is why we have maintenance plans/disaster recovery plans). I'll mention that other databases also have regulatory data too. What types of questions do I need to ask to determine if this is a sound decicion? (A DBA friend mentioned that if the service level agreement of said database does not radically differ from the others then why do they want to do this?) I have done some research on linked servers. What arguments should I bring forth about the fact that I have views setup that rely on data from other DBs currently?

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  • Oracle Database 12c

    - by David Allan
    Exciting day today as Oracle Database 12c is released. You can find lots of information on the release on OTN here. With this release comes another milestone on Oracle's Data Integration roadmap - OWB is no longer shipped with the database. You will notice that the OWB documentation is no longer included with the Oracle Database documentation, you can compare and contrast the 11.2 and 12.1 documentation below. OWB 11gR2 is still supported with Oracle Database 12c, you will need 11.2.0.3 plus at least CP2 which has been certified with Oracle Database 12c. The 11.2.0.4 release will wrapper this into one install.

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  • If all variables are a subset of the superkey, is the database design 5NF? [migrated]

    - by Lukazoid
    I have a table called LogMessages, which has the following columns: Level A numeric value which represents Trace, Debug, Info, Warning, Error or Fatal Time A UTC time Message Foreign key to a Messages table Source Foreign key to a Sources table User Foreign key to a Users table From what I can see, all of these columns are a part of the super key; if any single value differs to an existing row, a new row can be created. My question is, does this design comply to fifth normal form? I am unsure as some groups of data will be repeating, however I don't believe this violates 5NF? (correct me if I'm wrong)

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  • What is the best database design for managing historical information? [closed]

    - by Emmad Kareem
    Say you have a Person table with columns such as: ID, FirstName, LastName, BirthCountry, ...etc. And you want to keep track of changes on such a table. For example, the user may want to see previous names of a person or previous addresses, etc. The normalized way is to keep names in separate table, addresses in a separate table,...etc. and the main person table will contain only the information that you are not interested in monitoring changes for (such information will be updated in place). The problem I see here, aside form the coding hassle due to the extensive number of joins required in a real-life situation, is that I have never seen this type of design in any real application (maybe because most did not provide this feature!). So, is there a better way to design this? Thanks.

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  • WP: Oracle Multitenant on SuperCluster T5-8: Study of Database Consolidation Efficiency

    - by uwes
    Consolidation in the data center is the driving factor in reducing capital and operational expense in IT today. This is particularly relevant as customers invest more in cloud infrastructure and associated service delivery. Database consolidation is a strategic component in this effort. Oracle Database 12 c introduces Oracle Multitenant , a new database consolidation model in which multiple Pluggable Databases (PDBs) are consolidated within a Container Database (CDB). While keeping many of the isolation aspects of single databases, it allows PDBs to share the system global area (SGA) and background processes of a common CDB . The white paper recently published on OTN: Oracle Multitenant on SuperCluster T5-8: Study of Database Consolidation Efficiency analyzes and quantifies savings in compute resources, efficiencies in transaction processing, and consolidation density of Oracle Multitenant compared to consolidated single instance databases (SIDBs) running in a bare-metal environment.

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  • How to deploy ASP.NET application with MS SQL server database

    - by Maddy
    I want to deploy my website with MS SQL server database. It's my first time and I have never done it before. What I have come to know from my googling is that I must have a domain(.com/.net/.co) and a host(for my web pages .aspx & .cs(confusion here if I can also deploy my database)). Now, I am not getting to where I have to deploy my database. If I also have to buy a seperate SQL Server database or a host consisting of every thing (means I can deploy both my ASP.NET application & database as well).

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  • How would one build a relational database on a key-value store, a-la Berkeley DB's SQL interface?

    - by coleifer
    I've been checking out Berkeley DB and was impressed to find that it supported a SQL interface that is "nearly identical" to SQLite. http://docs.oracle.com/cd/E17076_02/html/bdb-sql/dbsqlbasics.html#identicalusage I'm very curious, at a high-level, how this kind of interface might have been architected. For instance: since values are "transparent", how do you efficiently query and sort by value how are limits and offsets performed efficiently on large result sets how would the keys be structured and serialized for good average-case performance

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