The Structured Query Language (SQL) forms the backbone of most modern database systems. These links provide the best resources on the Net for neophytes and expert database administrators alike!
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.
The Structured Query Language (SQL) forms the backbone of all relational databases. This language offers a flexible interface for databases of all shapes and sizes and is used as the basis for all user and administrator interactions with the database. In this course, you'll learn the basics of using SQL to store, retrieve and manipulate information in a database.
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.
Database views allow you to easily reduce the complexity of the end user experience and limit their ability to access data contained in database tables by limiting the data presented to the end user. Essentially, a view uses the results of a database query to dynamically populate the contents of an artificial database table.
SQL includes a CASE statement that allows you to return varying results based upon the evaluation of expressions. You can use a CASE statement anywhere within a SQL statement that you would normally include an expression. CASE statements are often found in SELECT, UPDATE and DELETE statements as well as WHERE and IN clauses.
The INSERT command in SQL is used to add records to an existing table. Returning to the personal_info example from the previous section, let's imagine that our HR department needs to add a new employee to their database.
The DROP command allows us to remove entire database objects from our database.
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.
Looking for a definition of self-join? Find it in the About Databases Glossary!
Interested in the definition of concatenation? Find out in the About Databases glossary!
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, youÂ’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.
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.
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.
O'Reilly's SQL Cookbook is the best reference I've seen for skilled SQL developers. Modeled after a true cookbook, it offers many short snippets of SQL code designed to solve specific problems. You can pick and choose the ingredients you need to help complete your SQL project.
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.
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.
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.
This software-independent book takes a hands-on approach to learning SQL. After some brief introductory material, it dives right into developing SQL queries designed to meet specific goals. It's a great reference for those who occasionally use SQL and forget the details.
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.
Would you like to learn SQL? This tutorial will introduce you to the basics.
Our databases contain information that is vital to the continued operations of our organizations. In this article, your About.com Guide introduces the SQL commands used to control access to your database.
SQL provides several aggregate functions to assist with data summarization. In this article we explore the usage of SUM, AVG, COUNT, MIN and MAX.
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.
Just getting started with the Structured Query Language? This tutorial walks you through the process of creating tables and databases in SQL databases.
The SQL DELETE command allows the removal of some or all of the data stored in a relational database table.
SQL join statements allow you to combine data from two or more tables in your query results. Learn how to leverage this powerful technology to supercharge your database queries.
Learn to retrieve information from your database with the SQL SELECT statement. This tutorial provides an introduction to the basics of database queries.
The Structured Query Language provides the foundation for all relational database systems. Join us as we explore the fundamental concepts behind this powerful language.
SQL's CUBE and ROLLUP commands allow for the efficient summarization of data.
How can fuzzy logic be used to enhance SQL? Fuzzy Systems Solutions markets a tool that does just that! This series explains the basics.
The Web Developer's Virtual Library provides a very readable introduction to the Structured Query Language.
A tremendous resource for all database administrators! Philip Greenspun provides the complete text of an SQL reference book online.
Are your SQL queries as efficient as possible? BASIS Corporation provides a feature article describing SQL optimization techniques.
This online book from Que offers a three-week tutorial on the Structured Query Language. At the conclusion of the series of lessons, readers will have gained a solid understanding of SQL concepts.
