A topic that is essential for all SQL programmers and database designers. This session examines the mysteries of the English text that appears when an EXPLAIN is requested.

You will learn what the EXPLAIN facility is, how and where the text is generated, how to read the output, what spool sizes and estimated time really represent, and choices that can be made to affect the Optimizer. There is an explanation of topics such as confidence levels, aggregations and the various joins, including Merge, Exclusion and Product joins and also optimized versus non-optimized queries. At the end of this session you will be able to explain the EXPLAIN.

Topics include how EXPLAIN informs the user about table scans and sync scanning, multi-table joins, and various types of merge join processing. Additionally, we use EXPLAIN to look at merge joins versus sub-queries, exclusive merge joins and cartesian product joins. Finally, we look at how statistics are collected and used, and how minor changes in coding can affect the resultant EXPLAIN. Don’t miss this in-depth look at the value and usefulness of EXPLAIN to any Teradata environment which is serious about performance.

Through this course, you will learn about the EXPLAIN facility, how and where it is generated and how to read the output. An introduction to Visual Explain with examples will also be provided.

Key Points:

  • How to use EXPLAIN text to understand join processing
  • How statistics are collected and used by the plan being EXPLAINed
  • How different coding approaches affect EXPLAIN output

Release information: Updated for TD 13 & 14


Larry Carter, Senior Learning Consultant - Teradata Corporation
Alison Torres, Director, Teradata Warehouse Consulting - Teradata Corporation

This course is offered by the Teradata Education Network. To enroll online, click the Training URL link below to go to the TEN site and Log in. If you're not a member click browse, select your region, and search on the Course Number. Or to enroll by phone, call the Enrollment Center at 1-937-242-4460. Note: You must be a member to register for a course.

Audience: DWA, DW Application Specialist, DWArchitect/Designer, DW Technical Specialist

Course number 49911
Training URL http://www.teradata.com/t/ten/
Format Recorded webcast
Price $195.00
Credit hours 2.00