Fine-Tuning Your SQL Code for Better Performance

The need to provide reliable and fast database performance is one of those DBA tasks that can suddenly pop up at any time. Changing conditions can adversely affect a system that was previously exhibiting sterling performance. Users start complaining about slow response time and soon management is pressuring the database team to come up with a solution that solves the issue. Welcome to the wonderful world of database administration!

The problem faced by your DBAs is that there can be multiple reasons behind the degraded performance of their databases. Pinpointing the specific one can be difficult and may involve a substantial period of trying different approaches to narrow down and address the issue. In many cases, providing the required level of performance can be a never-ending proposition as systems and their usage patterns evolve. Problematic database performance can be a recurring thorn in the side of your database team.

What Causes Database Performance Issues?

A complicated question that needs to be answered before tackling the performance problems is what is behind the degraded response time that has end-users flocking to the phone. The issues could have been present since the system was implemented and have only become evident due to growth in the size of the database or an increase in the number of users. Environmental changes such as migrating to a new hardware platform can also contribute to problems in satisfying user requirements.

Some specific areas that are ripe for investigating performance problems include:

  • A slow network - Network performance impacts your whole IT environment and can be a major reason for slow database performance. Moving to the cloud or a new piece of hardware may have network implications that were not fully understood before the move. This kind of problem will require the assistance of system admins and the networking team as well as your DBAs.

  • Small buffer pool size - Databases use a buffer pool to store pages that have recently been written to or read by the system. A small pool stresses the disk system as data constantly needs to be moved in and out to make it available to the system. Additional memory can be configured for use by the database to minimize this problem.

  • Index issues - A poorly designed index structure can result in long-running queries that have an expensive execution plan. Missing indexes can also lead to disk performance problems and increase the number of deadlocks a database experiences. This is a design issue that may manifest itself over time as the volume of data grows.

  • Suboptimal SQL coding - The way the SQL coding was implemented can result in serious performance issues. This is also a design issue that may not become evident in testing or the initial phases of database deployment. Here are some potential coding errors that can be resolved to increase a system’s response time.

  • Coding loops should be avoided where they can be replaced by INSERT of UPDATE statements. Removing SQL queries from being executed inside loops can often result in improved performance.

  • Correlated SQL subqueries are statements where a value is used from a parent query. They should be avoided, as additional queries are required as each row is executed, which leads to degraded performance.

  • Avoid the use of SELECT * statements. A better solution is to call for the specific columns that you need. You can save a tremendous amount of time and processing by eliminating the use of this type of SQL statement.

Improving Database SQL Code

IDERA’s DB Optimizer can be just the tool to enable your DBA team to address tuning their SQL code. Advanced techniques such as visual SQL tuning diagrams make it easier for your team to successfully identify the modifications that need to be made. Index analysis shows which indexes are being used and can locate missing indexes and offer recommendations to optimize performance. Graphical visualization of wait-time analysis quickly pinpoints the code responsible for system bottlenecks.

DB Optimizer facilitates SQL code optimization across a range of database platforms from one interface for enhanced DBA productivity. The tool supports SQL execution tuning and workload profiling for SQL Server, Oracle, Sybase, and IBM Db2.  You can also perform execution tuning on JDBC systems. Database instances on-premises and on cloud virtual machines are supported by DB Optimizer.

Your SQL code may need to be tuned at irregular intervals to address performance issues. Having a reliable tool like DB Optimizer makes it more likely that your team can identify and correct coding issues that are slowing down database response time, keeping everybody happy.

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