Databases: Most Popular Articles
Database normalization can save storage space and ensure the consistency of your data. Learn the basics in this introductory article.
What is a primary key? Find out here!
You can use SQL JOIN statements to combine data from three or more tables. In an earlier article, we took a look at using inner joins and outer joins to combine data from two different tables. In many cases, you’ll want to take this a step further and combine data from three or more tables. Let's take a look at the SQL statements that allow you to accomplish this goal for an inner join.
This free Access database of ZIP codes provides database designers with a valuable tool to assist in mapping ZIP codes to a city/state pair and even provides the latitude and longitude of that location.
SQL joins allow you to retrieve data from multiple database tables. Your About.com Guide to Databases provides a comprehensive introduction.
Facts and dimensions form the core of any business intelligence effort. These tables contain the basic data used to conduct detailed analyses and derive business value. In this article we take a look at the development and use of facts and dimensions for business intelligence.
Databases are designed to offer an organized mechanism for storing, managing and retrieving information. They do so through the use of tables. If youre familiar with spreadsheets like Microsoft Excel, youre probably already accustomed to storing data in tabular form. Its not much of a stretch to make the leap from spreadsheets to databases.
What is Referential Integrity? Find out in our database glossary!
What is a database? Find out here!
Looking for a book to help you get started with Strucutred Query Language? Need a new reference book for your shelf? Check out my favorite SQL books.
Want to learn how to use Microsoft Access? Find out on the About.com Databases site!
Microsoft SQL Server provides the stored procedure mechanism to simplify the database development process by grouping Transact-SQL statements into manageable blocks.
As you may already know, databases use tables to organize information. Each table consists of a number of rows, each of which corresponds to a single database record. So, how do databases keep all of these records straight? Its through the use of keys.
In this series of Microsoft Access tutorials, we follow the database administrators for Patrick's Widgets as they build a Microsoft Access database from the ground up.
Are you new to the world of databases? Wondering where to get started? In this series of articles, we introduce you to the basics of database technology and help you get started in this exciting field.
This free Access database of area codes provides database designers with a valuable tool to assist in mapping area codes to a state, province or region.
In our first article, we looked at the basic requirements of 3NF. Here they are again to refresh your memory: meet the requirements of 1NF and 2NF and remove columns that are not fully dependent upon the primary key.
Relationships allow you to describe the connections between different database tables in powerful ways. Once you’ve described the relationships between your tables, you can later leverage that information to perform powerful cross-table queries, known as joins.
What is a query? Find out here! Databases.
Would you like to learn SQL? This tutorial will introduce you to the basics. Page 2.
The release of Access 2007 brings a new file format. The MDB database files weve known for over a decade are now slated to become historical relics. While Access 2007 continues to support MDB databases for backwards compatibility purposes, Microsoft has now introduced the new ACCDB file format as the future standard. Wondering if you should begin using the ACCDB format?
In this article, we begin our look at the first of three major normal forms -- first normal form (otherwise known as 1NF).
What is the domain of a database? Find out here!
The bulk copy (bcp) command of Microsoft SQL Server provides you with the ability to insert large numbers of records directly from the command line. In addition to being a great tool for command-line aficionados, bcp is a powerful tool for those seeking to insert data into a SQL Server database from within a batch file or other programmatic method.
The software that allows a computer to perform database functions of storing, retrieving, adding, deleting and modifying data.
Learn to retrieve information from your database with the SQL SELECT statement. Your About.com Guide to Databases provides a thorough introduction.
What is a foreign key? Find out here!
The SQL DELETE command allows the removal of some or all of the data stored in a relational database table.
Database dependencies are a topic that often confuses both students and database professionals alike. Fortunately, they are not that complicated and can best be illustrated through the use of a number of examples. In this article, we examine common database dependency types.
Learn to create databases and tables using the Structured Query Language (SQL) in this step-by-step tutorial from your About.com Guide to Databases.
The MySQL database server is one of the most popular open source databases in the world. Although administrators typically install MySQL on a server operating system, it’s certainly possible to install it on a desktop operating system like Windows 7. Once you do so, you’ll have the tremendous power of the flexible MySQL relational database available to you for free. It’s an extremely useful database for both developers and system administrators. Installing MySQL on Windows 7 is an especially valuable tool for those seeking to learn database administration but lack access to a server of their own. Here’s a step-by-step walkthrough of the process.
You've finally buckled down and decided that it's time to purchase a database solution for your home or business. What type of database do you need? It's actually a simple matter of deciding what features you need and choosing a product that meets your requirements and doesn't cause too much pain in your pocketbook.
The transaction log plays a critical role in a SQL Server database: it maintains an ongoing record of database activity crucial for the restoration of recent data in the event of a disaster. However, this benefit comes at a cost: the transaction log can consume a substantial amount of space in an active database. SQL Server provides two actions designed to counterbalance these large space requirements: transaction log truncation and log file shrinking.
Looking for an easy way to move your Microsoft Access database to the cloud? Microsoft’s Office 365 service provides a central location where you can store and manipulate your Microsoft Access databases. This service has multiple benefits including leveraging Microsoft’s highly available environment to protect your data and enabling multiuser access to your database in a scalable fashion. In this article, we look at the process of moving your Microsoft Access database to Office 365.
Just getting started with databases? Here's a rundown of the top things that I wish I knew before I got started in the field. These facts are guaranteed to make your life easier!
The Structured Query Language (SQL) is the set of instructions used to interact with a relational database. In fact, SQL is the only language that most databases actually understand. Whenever you interact with such a database, the software translates your commands (whether they are mouse clicks or form entries) into SQL statement that the database knows how to interpret.
Microsoft provides quite a few prebuilt database templates to assist you in jumpstarting your database development process. In this tutorial, we'll walk through the process of creating an Access database using these templates.
Second Normal Form allows you to enhance the normalization of your database. In this article, we explore the requirements of 2NF and the process of normalizing your database.
Looking for a job in the database field? This article provides the advice you need to get started.
What is a Candidate Key? Find out here!
Are you ready to convert your unwieldy Excel spreadsheet to a flexible Access database? Let us walk you through the process!
Is your Access database growing too large or unwieldy? Perhaps you need to allow more robust multiuser access to the database? Converting your Access database to Microsoft SQL Server might be the solution you’re trying to find. Fortunately, Microsoft provides an Upsizing Wizard in Access that makes it easy to convert your database. In this tutorial, we walk through the process of converting your database.
Entity Relationship diagrams (also known as E-R or ER diagrams) provide database designers with a valuable tool for modeling the relationships between database entities in a clear, precise format. This industry standard approach uses a series of block shapes and lines to describe the structure of a database in a manner understandable to all database professionals. Many database software packages, including Microsoft Access, SQL Server, and Oracle, provide automated methods to quickly create E-R diagrams from existing databases.
The COUNT() function in SQL allows you to count database records based upon a variety of criteria. You can use it to count all records in a table, count unique values in a column or count the number of times records occur that meet certain criteria. This tutorial takes a brief look at each of these scenarios.
Databases depend upon keys to store, sort and compare records. If you’ve been around databases for a while, you’ve probably heard about many different types of keys – primary keys, candidate keys, and foreign keys. When you create a new database table, you’re asked to select one primary key that will uniquely identify records stored in that table.
The Northwind database contains some great sample tables, queries, reports and other database features. Here's how to install it.
All database management systems should share four characteristics: Atomicity, Consistency, Isolation and Durability.
You can use a self-join to simplify nested SQL queries where the inner and outer queries reference the same table. These joins allow you to retrieve related records from the same table.
Want to create dynamic, server-generated HTML from your Access database? This step-by-step tutorial will walk you through the process.
Create a New SQL Server Agent Job.
What is a functional dependency? Find out here!
SQL's CUBE and ROLLUP commands allow for the efficient summarization of data. Learn how to use them here!
Want to learn how to create a query in Microsoft Access? Find out on the About.com Databases site!
Most large-scale databases use the Structured Query Language (SQL) to define all user and administrator interactions. This language offers a flexible interface for databases of all shapes and sizes.
Join us as we walk through the process of creating database relationships in Microsoft Access.
It's important to do a careful needs analysis before you dive in and commit to a database solution. Learn the difference between desktop and server databases.
Sample Excel Document. Databases.
Desktop databases offer simple, flexible solutions for data storage and retrieval. They're often quite sufficient to meet uncomplicated database requirements for both small and large organizations. If you're not sure if a desktop database is right for you, try reading the Choosing a Database series of articles which cover both desktop and server databases in depth
What is Boyce-Codd Normal Form (BCNF)? Find out here!
JOIN operations allow us to combine data from multiple tables. Learn how these operations treat the NULL value.
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Would you like to create professional-looking reports from your Microsoft Access database with the click of a mouse? Follow along as we walk through the simple process of designing a reusable report.
In an earlier article, we reviewed the process for creating an Access database from a template. While this is certainly an agreeable, easy approach to building a database, there isn’t always a template available that meets your needs. In this article, we review the process for creating an Access database from scratch.
Database normalization is one of the sacred cows of application development. Every undergraduate programming course you’ve taken or book you’ve read likely preaches about the importance of normalizing databases in an almost religious fashion. You’re made to feel like failure to normalize a database is tantamount to violating one of the laws of the universe. It’s time to challenge that truism. Sometimes it’s OK to denormalize your database
Microsoft SQL Server 2008 offers administrators two choices of performing user authentication: Windows authentication mode and mixed authentication mode. Making the proper choice affects both the security and maintenance of your organization’s databases.
Did you know that you can view and edit the SQL statements that drive every Microsoft Access database query? In this article, we take a look at the process of accessing the underlying SQL code and tweaking it to perfect Access queries.
You may use basic SQL queries to retrieve data from a database but this often doesn’t provide enough intelligence to meet business requirements. SQL also provides you with the ability to group query results based upon row-level attributes in order to apply aggregate functions using the GROUP BY clause.
There are many applications where you may wish to add a date/time stamp to each record, identifying the time that the record was added to the database. It’s easy to do this in Microsoft Access using the Now() function. In this tutorial, I explain the process step-by-step.
Looking to optimize the performance of your SQL Server database? If your database contains very large tables, you may benefit from partitioning those tables onto separate filegroups. This technology, introduced in SQL Server 2005, allows you to spread data onto different physical disks, leveraging the concurrent performance of those disks to optimize query performance.
One of the most important concepts in databases is creating relationships between database tables. These relationships provide a mechanism for linking data stored in multiple tables and retrieving it in an efficient fashion. In order to create a link between two tables, you must specify a foreign key in one table that references a column in another table.
SQL Server user-defined functions and stored procedures offer similar functionality. Both allow you to create bundles of SQL statements that are stored on the server for future use. This offers you a tremendous efficiency benefit, as you can save programming time by...
Are you interested in tracing your family roots but don’t have a good place to store all of your genealogical information? While there are several full-featured family tree software packages on the market, you can also use a free Microsoft Access template to create your own genealogy database on your computer. Microsoft’s already done most of the work for you, so there is no programming knowledge needed to get started.
SQL Server provides three different recovery models that allow you to specify the way SQL Server manages log files and prepares your enterprise for a disaster. Each of these models represents a different approach to balancing the tradeoff between conserving disk space and providing for granular disaster recovery options.
Summarize data with SQL's SUM, AVG, MIN, MAX and COUNT functions. Your About.com Guide to Databases walks you through the process.
The TRY…CATCH statement in Transact-SQL allows you to detect and handle error conditions gracefully within your database applications. This statement is the cornerstone of SQL Server error handling and is an extremely important part of developing robust database applications.
Free Practice Test for Microsoft Exam 70-432 Microsoft SQL Server 2008, Implementation and Maintenance
The Data Control Language (DCL) is a subset of the Structured Query Lanaguge (SQL) that allows database administrators to configure security access to relational databases. It complements the Data Definition Language (DDL), which is used to add and delete database objects, and the Data Manipulation Language (DML), which is used to retrieve, insert and modify the contents of a database.
Microsoft Access allows you to export data to a variety of formats for sharing and analysis. In this tutorial, we walk through the process of exporting an Access table to an Excel workbook.
This Microsoft Access sample database provides tables containing information on the world's countries, cities and provinces. It is used to illustrate examples for a number of the articles on the About Databases site and also provides a good sample for students, professionals and others who are learning Microsoft Access.
Part VIII of our tutorial introduces you to the concept of Access forms to input and modify data.
Looking to prove your SQL Server Administration mettle? This quiz will help you prepare for Microsoft's 70-228 exam: Installing, Configuring, and Administering Microsoft SQL Server 2000 Enterprise Edition. This is a critical step toward earning your Microsoft Certified Database Administrator credential.
SQL Injection attacks pose tremendous risks to web applications that depend upon a database backend to generate dynamic content. In this type of attack, hackers manipulate a web application in an attempt to inject their own SQL commands into those issued by the database. In this article, we take a look at several ways you can test your web applications to determine whether they're vulnerable to SQL Injection attacks.
This sample Excel document contains student course registration data for use in generating pivot tables. It should be used in conjunction with the Creating Pivot Tables in Excel 2010 tutorial found on this site.
This sample Excel spreadsheet provides a starting point for our Microsoft Access tutorials.
Microsoft Access allows you to include attachments in database tables. You may store photos, graphics, documents and other files in your Access database using Microsoft's Object Linking and Embedding (OLE) technology. Database attachments are a new feature in Access 2007.
Looking for a definition of a database relationship? Check out the About Databases glossary definition!
Microsoft SQL Server provides users with a variety of rich graphical user interfaces to retrieve and manipulate data and configure SQL Server databases. However, sometimes it’s just easier to work from the old-fashioned command line. Whether you’re looking for a quick-and-dirty way to execute a SQL query or wish to include SQL statements in a Windows script file, SQLCMD allows you to meet your goal.
What is a database schema? Find out here!
The MySQL database server is one of the most popular open source databases in the world. Although there is not yet an official package for installing it on the latest version of the Macintosh operating system (Mac OS X 10.7, codenamed Lion), it is possible to install the database on such a system using the package designed for Mac OS X 10.6. Here’s a step-by-step walkthrough of the process.
The Structured Query Language (SQL) is the language of databases. All modern relational databases, including Access, FileMaker Pro, Microsoft SQL Server and Oracle use SQL as their basic building block. In fact, it’s often the only way that you can truly interact with the database itself.
Microsoft SQL Server provides a robust replication facility to distribute and update data in a decentralized fashion.
What is a multivalued dependency? Find out here!
UNIQUE constraints allow SQL Server administrators to specify that a column may not contain duplicate values. When you create a new UNIQUE constraint, SQL Server checks the column in question to determine whether it contains any duplicate values. If the table contains preexisting duplicates, the constraint creation command fails. Similarly, once you have a UNIQUE constraint on a column, attempts to add or modify data that would cause duplicates to exist also fail.
SQL Server databases rely upon tables to store data. In this tutorial, we'll explore the process of designing and implementing a database table in Microsoft SQL Server.
Traces allow you to track the specific actions performed against a SQL Server databases. They provide valuable information for troubleshooting database issues and tuning database engine performance. In this tutorial, we walk through the process of creating a SQL Server Trace with SQL Server Profiler, step-by-step.
What is a superkey? Find out here!
If youre a Microsoft Office power user, you might be familiar with the encryption features of Word, PowerPoint and Excel. These programs all allow file owners to easily apply encryption. Unfortunately, Microsoft Access doesnt offer similar functionality, but it still has relatively powerful security functionality. In this article, well take a look at Microsoft Access user-level security, a feature that lets you specify the level of access to grant each individual user of your database.
The NoSQL movement is changing the way we think about databases. Instead of requiring that database developers follow the rigid principles of the ACID model, NoSQL allows a great deal of flexibility that provides a tremendous efficiency boost. This comes, however, at the cost of reduced enforcement of traditional database constraints.
Glossary of database related terms, including definitions, explanations, examples, suggested reading, and other resources.
Looking for advice on using the Structured Query Language? The About Databases SQL FAQ provides answers to the most frequently asked questions about SQL and databases.
Are you ready to convert your unweildy Excel spreadsheet to a flexible Access database? Let us walk you through the process!
Popular database certifications are always in demand, whether it's Microsoft's MCTS or MCITP, Oracle's OCA, OCP and OCM or MySql's CMA, CMDEV and CMDBA. Are you a database professional seeking to polish your resume in the hopes of landing a better gig? Database vendors offer a variety of professional certification programs that can help you advance your career while gaining valuable technical skills.
Looking for a definition of a database instance? Look no further!
In the seventh installment of our Building an Access Database From the Ground Up series, we create relationships between our tables to finish implementing our relational model.
An attribute, when in regards to databases, deals with single data in an object. It is one of the basic terms used in SQL.
The date and time SQL Server data types are used to store calendar information. They include the datetime, smalldatetime and timestamp variables.
Learn how to create a simple form in Microsoft Access. This tutorial walks you through the process step-by-step!
Free Practice Test for Microsoft Exam 70-433 Microsoft SQL Server 2008 Database Development Welcome to
Join us as we walk through the process of creating database relationships in Microsoft Access.
What is a transitive dependency? Find out here!
Did you know that you can use a self-join to simplify nested SQL queries where the inner and outer queries reference the same table? Let's take a look at an example.
With the release of MySQL 5.0, the popular open source database platform added one of the most long-awaited features: the ability to use stored procedures. Long a staple of commercial database systems, such as Microsoft SQL Server and Oracle, stored procedures provide database developers with a powerful tool.
The Structured Query Language (SQL)provides database users with the ability to create customized queries to extract information from databases. In an earlier article, we explored extracting information from a database using SQL SELECT queries. Let's expand upon that discussion and explore how you can perform advanced queries to retrieve data that matches specific conditions.
SQL Server provides fourmethods you can use when you need to insert large quantities of data into a SQL Server database. These automated techniques will help you insert data from the results of a SQL query, a text file or another database.
Binary data types allow you to store any type of binary data, including entire files of up to 2GB. They include binary, varbinary, image and bit.
Users new to the world of databases are often confused by a special value particular to our field – the NULL value. Read about the proper uses of NULL in this article.
SQL’s UNION command allows you to combine the results of two or more database queries that are not necessarily linked through a database relationship. For example, imagine that you have a school database and wish to use it to create a master contact list for all students, faculty and staff. Looking at your database, you discover that the records corresponding to each of these constituencies appears in separate database tables.
Data mining allows you to find the needles hidden in your haystacks of data. Learn how to use these advanced techniques to meet your business objectives.
Although Access provides a convenient spreadsheet-style datasheet view for entering data, it isn’t always an appropriate tool for every data entry situation. If you’re working with users you don’t want to expose to the inner workings of Access, you may choose to use Access forms to create a more user-friendly experience. In this tutorial, we’ll walk through the process of creating an Access form.
The MySQL database server is one of the most popular open source databases in the world. Although there is not yet an official package for installing it on the latest version of the Macintosh operating system (Mac OS X 10.8, codenamed Mountain Lion), it is possible to install the database on such a system using the package designed for Mac OS X 10.6, just as it was possible to do so on Mac OS X 10.7 Lion. Once you do so, you’ll have the tremendous power of the flexible MySQL relational database available to you for free. It’s an extremely useful database for both developers and system administrators. Here’s a step-by-step walkthrough of the process.
Starting from a template is the easiest way to get up and running quickly with Microsoft Access. Using this process allows you to leverage the database design work initially performed by someone else and then customize it to suit your particular needs. In this tutorial we walk you through the process of creating a Microsoft Access database using a template to get you up and running in just a few minutes.
The DISTINCT keyword in SQL allows you to select only those records that contain unique values for the columns requested in a SELECT statement. Duplicate values are ignored and only displayed once.
The SELECT command is the most commonly used command in SQL. It allows database users to retrieve the specific information they desire from an operational database.
Backing up your Microsoft Access databases is an important part of protecting your critical data. In this tutorial, we walk through the process of backing up an Access database, step-by-ste.
SQL Server allows you to automatically notify database administrators when unusual circumstances occur. This powerful alerting mechanism enables 24-hour monitoring of your database performance without staffing a 24-hour operations center.
NOT NULL constraints in Microsoft SQL Server allow you to specify that a column may not contain NULL values. When you create a new NOT NULL constraint on a database column, SQL Server checks the column’s current contents for any NULL values. If the column currently contains NULL values, the constraint creation fails. Otherwise, SQL Server adds the NOT NULL constraint and any future INSERT or UPDATE commands that would cause the existence of a NULL value fail.
The true power of relational databases lies in their ability to track relationships (hence the name!) between data elements. However, many database users don’t understand how to take advantage of this functionality and simply use Access as an advanced spreadsheet. In this tutorial, we’ll walk through the process of creating a relationship between two tables in an Access database.
Selecting appropriate data types is one of the most important considerations when designing a SQL Server database. Choices you make in the database design phase may have a significant impact on the efficiency, performance and storage requirements of your database down the road.
The definition of trivial functional dependency in relational database theory, along with an example and some further reading.
Database Maintenance Plans allow you to automate many database administration tasks in Microsoft SQL Server. You can create maintenance plans using an easy wizard-based process without any knowledge of Transact-SQL.
Would you like to share your Access reports with the web? This step-by-step tutorial will walk you through the process.
Do your databases contain fields where users have entered a mess of information in a variety of different formats? Microsoft Access input masks may help you alleiviate this inconsistency in your desktop databases. Input masks allow you to specify the format of allowable user input, preventing users from entering information in a form that does not meet your data quality requirements.
According to most sources, Microsoft is rapidly gaining market share in the RDBMS arena. Have they finally surpassed Oracle? Read the latest results!
Are you ready to convert your unwieldy Excel spreadsheet to a flexible Access database? Let us walk you through the process!
What is classification? Learn about this data mining term here.
SQL joins allow you to retrieve data from multiple database tables. Your About.com Guide to Databases provides a comprehensive introduction. Page 2.
k-means clustering is a data mining/machine learning algorithm used to cluster observations into groups of related observations without any prior knowledge of those relationships. The k-means algorithm is one of the simplest clustering techniques and it is commonly used in medical imaging, biometrics and related fields.
Over time, Microsoft Access databases grow in size and unnecessarily use disk space. Additionally, repeated modifications to the database file may result in data corruption. Therefore, it's a good idea to periodically run the compact and repair database tool to ensure the consistency of your data.
Character string data types are used to store text values in Microsoft SQL Server databases.
Are you overwhelmed by the large quantities of data that need to be tracked in your organization? Perhaps you're currently using a paper filing system, text documents or a spreadsheet to keep track of your critical information. If you're searching for a more flexible data management system, a database might be just the salvation you're looking for and Microsoft Access 2013 provides an excellent option.
Oftentimes, you wish to share data with users in your organization who may, in turn, wish to create their own forms and reports. While you may want them to have the ability to view and/or update your data, you may not wish them to modify the interface you use to work with the data yourself. Fortunately, Microsoft Access provides the ability to split a database into front-end and back-end components. You can safely share data with other users while keeping your interface private.
With the release of SQL Azure, Microsoft is now offering serious database users the ability to put their databases in the cloud. SQL Azure is a relational database that supports Transact-SQL using Microsoft SQL Server Technology but allowing you to place all of the server and operating system administration tasks in the hands of Microsoft Engineers.
It’s very tempting to simply come up with something off the top of your head and run with it, but that’s not a great practice. Either you or your successors will curse the difficult field names you created down the road. In this article, I offer my advice on creating logical, consistent names for database fields, tables, reports, stored procedures and other objects.
What is Second Normal Form? Find out here!: acme widgets fred flintstone abc corporation john doe two tables
Want to learn how to modify a query in Microsoft Access? Find out on the About.com Databases site!
SQL Server constraints allow you to enforce rules in your database. These rules may affect business logic, database integrity and/or table structures. Each one plays an important role in your database architecture.
The Health Insurance Portability and Accountability Act of 1996 (HIPAA) places a large regulatory burden on organizations that deal with certain types of health-related information. We're now only a couple of weeks away from the compliance deadline for the Security Rule. Are you ready for April 21st?
What is Third Normal Form? Find out here!: state zip code database designers abc corporation city state zip columbia md 21046
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If you’re looking for some of the flexible query power of a database but don’t want to mess with relational database design, pivot tables may be just the technology you need. Chances are you’re already using one of the popular spreadsheet packages that include this technology, such as Microsoft Excel or the free Google Spreadsheets package.