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Blogs
Toad and Database Commentaries |
Toad World blogs are a mix of insightful how-tos from Quest experts as well as their commentary on experiences with new database technologies.
 Do you have a topic that you'd like discussed? We'd love to hear from you. Send us your idea for a blog topic.
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Author: |
RichardTo |
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Monday, October 30, 2006 2:28 PM |
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Solving problems in your SQL code, tune queries, and share new tips, tricks, and techniques |
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From SQL Optimization Hints to Plan Instructions |
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RichardTo
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Wednesday, May 02, 2007 7:05 AM
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Most database vendors provide optimization hints which enable a user to influence the decision the database SQL optimizer will make when determining which execution plan it will choose. Oracle provides a full set of optimization hints to help users to rectify an i ...
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Dummy SQL Transformation Rules? |
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RichardTo
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Thursday, March 01, 2007 10:33 AM
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I have been asked many times that why there are some dummy SQL transformations/rewrites that look meaningless, but it works in certain situations. Let me give you some examples that may help to explain what theory on behind of Quest SQL Optimizer.
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Transformation Rules Relating to Index Usage |
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RichardTo
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Friday, February 09, 2007 8:25 AM
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In Quest SQL Optimizer, transformation rules relating to index usage are designed to guide the database SQL optimizer as to how it should use the indexes for a specific SQL statement. Although those rules may familiar to most of SQL developers, but it is still worth to illustrate some commonly used rules for SQL beg ...
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How to control many table join |
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RichardTo
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Wednesday, January 03, 2007 3:42 PM
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In my last blog, I use two tables join to illustrate the simple path control, now let’s use a three table join SQL statement to demonstrate a more complicated scenario. Let’s assume that A.key, B.key and C.key are all indexed.
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How to Control Two Tables Join Path? |
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RichardTo
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Thursday, December 07, 2006 3:06 PM
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In old version of Oracle database, it is easy to control the join path by reordering the tables in table list after the FROM clause, but it is getting difficult to control the join path in today’s cost based SQL optimizer, I am going to introduce method that is applicable in most databases such as Oracle, Sybase, DB2 and SQL Server in the following:
To control a join path, we cannot tell the database SQL optimizer which path is the best one to select. Instead, we add something to the syntax of the SQL statement that causes an increase to the cost of the current join path selected by database SQL optimizer. Let’s take a look at the following example of two table join scenarios.
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Why Join Path Matters |
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RichardTo
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Monday, November 13, 2006 12:28 PM
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The Nested Loop join operation is the basic join operation which is supported by most RDBMS, since it requires less memory and less temporary space. Normally, it can provide faster data response time than other join operations. But, the path of a Nested Loop join will significantly affect the speed of the join operation. Let’s use a two table join as an example to understand how this works.
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Why SQL Tuning? |
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RichardTo
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Monday, October 30, 2006 2:28 PM
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For years, commercial database manufacturers have fought an endless battle to improve the performance of inserting, updating, deleting, and retrieving information stored in the database. Despite their continual efforts and hard work, we have not seen a significant improvement in the performance of most Relational Database Management Systems (RDBMS). Users still suffer from under-performing SQL statements and database expe ...
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