Book Image

Teradata Cookbook

By : Abhinav Khandelwal, Viswanath Kasi, Rajsekhar Bhamidipati
Book Image

Teradata Cookbook

By: Abhinav Khandelwal, Viswanath Kasi, Rajsekhar Bhamidipati

Overview of this book

Teradata is an enterprise software company that develops and sells its eponymous relational database management system (RDBMS), which is considered to be a leading data warehousing solutions and provides data management solutions for analytics. This book will help you get all the practical information you need for the creation and implementation of your data warehousing solution using Teradata. The book begins with recipes on quickly setting up a development environment so you can work with different types of data structuring and manipulation function. You will tackle all problems related to efficient querying, stored procedure searching, and navigation techniques. Additionally, you’ll master various administrative tasks such as user and security management, workload management, high availability, performance tuning, and monitoring. This book is designed to take you through the best practices of performing the real daily tasks of a Teradata DBA, and will help you tackle any problem you might encounter in the process.
Table of Contents (19 chapters)
Title Page
Dedication
Packt Upsell
Contributors
Preface
Index

Improving left join


There can be two kinds of left joins, or outer joins:

  • Left outer join
  • Right outer join

This type of outer join will return all rows from the left or right table, and only those rows that match from the right or left table. This is handy when there may be missing values in the other table, but you want to get a description or other information from the other table. The following image shows the working of outer joins, represented as a VENN diagram:

Rows for which matching values are derived will be NULL in each case of join.

Getting ready

You need to connect to the Teradata database using SQLA or Studio. Identify the query in which left join is causing performance issues. 

 

How to do it...

  1. Connect to the Teradata database using SQLA or Studio.
  2. Write SHOW in front of the query and execute it to get the list of all objects in the query, with their definitions.
  3. Once you have DDLs of all the objects, check the columns involved in joins.
  4. Execute EXPLAIN for the query by pressing F6 in...