Organizations that optimize SQL Queries can increase their operational efficiency and benefit from accelerated time-to-market.
Database administrators (DBAs) have busy jobs that require them to perform a wide variety of diverse activities. Optimizing SQL queries may not seem to be very important when compared to tasks like ensuring databases are backed up and available to their users. Maintaining robust security measures to protect enterprise data resources is another critical part of a DBAs job that needs to be given high priority.
The availability and performance of a database and its associated applications are what concern end-users. They want to reliably access systems and enjoy a high level of performance that results in fast response times. Next to unavailability, DBAs will face more complaints from users regarding poor performance than anything else.
That’s where SQL query optimization comes in. Modern databases are complex creatures that present multiple opportunities for mistakes made in configuration or hardware provisioning that can lead to degraded performance. Ill-formed SQL queries can drag down database response time despite other attempts at improving performance. For this reason, SQL queries must be optimized.
Anatomy of a SQL Query
Structured Query Language or SQL is the query language that is most often used by DBAs. A subset of SQL called Data Manipulation Language is used to create queries that interrogate and extract data from a database and format it into human-readable form.
A SQL query consists of two mandatory and two optional blocks of code that determine what data is returned and how it is formatted. Specific keywords are used in each of the four code blocks.
Mandatory code blocks
- The SELECT keyword identifies the information requested to be returned by the query.
- The FROM keyword identifies the data source used to fulfill the SELECT request.
Optional code blocks
- A WHERE statement sets parameters that limit the data elements returned by the query.
- GROUP BY or ORDER BY statements are used to control the way returned data is displayed.
From these simple building blocks, incredibly complex SQL queries can be defined and executed. But there can be a substantial difference in the amount of time required to complete a query based on how it is coded and structured. Finding inefficient queries and tuning them can have a tremendously positive impact on database performance.
Optimizing SQL Queries
One of the factors that affect the performance of SQL queries is the amount of data that needs to be scanned to return the requested results. The number of concurrent transactions being performed on the database by a large user community can also slow down query performance.
DBAs have no control over the popularity of their databases or the number of users vying for system resources. But they can tune the SQL queries user are executing. One method of accomplishing this goal is to eliminate the retrieval of unnecessary data. Minimizing the amount of data that needs to be queried to obtain the result will invariably speed up database response time.
The goal is to limit the number of rows and columns used to satisfy the query. A simple example will suffice to illustrate how a small modification in an SQL query can have a huge impact on its execution speed.
A lazy way to ensure that all data in a table that might be useful for query processing is included makes use of a SELECT * statement. This pulls in all rows and columns in an attempt to locate the requested data. In almost every case, additional processing time is required to search through data that is essentially irrelevant to the success of the query.
Tuning a query by selecting a subset of columns and rows is a much more efficient method of retrieving information from a database. The use of parameters on the SELECT statement as well as limiters specified on a WHERE statement can exponentially reduce the amount of time required to satisfy a query. Searching for opportunities to improve the performance of SQL queries is what query optimization is all about.
The Right Tool for SQL Query Optimization
IDERA’s DB Optimizer is a SQL query optimizing tool that supports Oracle, SQL Server, Db2, and Sybase systems from a single unified interface. A SQL tuning wizard enables even novice DBAs to efficiently tune SQL queries. The tool provides tuning recommendations and displays SQL code graphically in Visual SQL Tuning (VST) diagrams.
DB Optimizer identifies the SQL code that leads to degraded database performance. Simulate production environments and use load testing to check on the performance of existing SQL code and to try alternatives. Run queries multiple times in parallel to test improvements without impacting your production environment. The tool offers DBAs a comprehensive platform from which to tune and optimize SQL queries.
DB Optimizer can be purchased as a stand-alone application or as part of the DB PowerStudio suite of database tools. DB PowerStudio is a collection of four tools that enable teams to administer systems, manage changes, tune queries, and develop relational databases. All of the tools can be test-driven during a 14-day, fully-functional trial period. You’ve got nothing to lose except maybe some unnecessary query processing time.