COLLECT DEMOGRAPHICS | SQL Statements | Teradata Vantage - 17.05 - COLLECT DEMOGRAPHICS - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Manipulation Language

Product
Advanced SQL Engine
Teradata Database
Release Number
17.05
Release Date
January 2021
Content Type
Programming Reference
Publication ID
B035-1146-175K
Language
English (United States)

Collects various table demographic estimates and writes the data to the DataDemographics table of a user-defined QCD database for subsequent analysis by the Teradata Index Wizard.

For more information about index analysis, see:

ANSI Compliance

COLLECT DEMOGRAPHICS is a Teradata extension to the ANSI SQL:2011 standard.

Required Privileges

You must have all of the following privileges to perform COLLECT DEMOGRAPHICS:
  • DELETE on the DataDemographics table in QCD_name.
  • INSERT on the DataDemographics table in QCD_name or INSERT on the QCD_name database.
  • SELECT on the specified tables or containing databases or users.

Invocation

Normally invoked using the Teradata Index Wizard utility or the Visual Explain tool.

Demographics Collected

COLLECT DEMOGRAPHICS determines and writes the following information for each specified table into the DataDemographics table of the specified query capture database:
  • Subtable type
  • Subtable ID
  • Estimated cardinality
  • Estimated average row length
  • Various system-related information

One row of information is collected in the appropriate DataDemographics subtable of the specified QCD for each AMP that is online at the time the request is performed.

COLLECT DEMOGRAPHICS does not capture information for the QCD table TableStatistics. TableStatistics is used only during the collection of statistics invoked by performing an INSERT EXPLAIN … WITH STATISTICS or COLLECT STATISTICS (QCD Form) request.

For more detailed information, see Teradata Vantage™ - SQL Request and Transaction Processing, B035-1142.

Relationship to INSERT EXPLAIN WITH STATISTICS AND DEMOGRAPHICS

The information retrieved for COLLECT DEMOGRAPHICS and INSERT EXPLAIN WITH STATISTICS AND DEMOGRAPHICS is identical. The principal differences are:
  • INSERT EXPLAIN WITH STATISTICS AND DEMOGRAPHICS uses an SQL query to collect the information, while COLLECT DEMOGRAPHICS obtains the information directly.
  • Demographics captured by INSERT EXPLAIN WITH STATISTICS AND DEMOGRAPHICS are automatically deleted whenever you delete the relevant query plans.

    Demographics captured by COLLECT DEMOGRAPHICS are not deleted when you perform associated DROP actions on the subject table and must be deleted explicitly.

COLLECT DEMOGRAPHICS Not Supported From Macros

You cannot specify a COLLECT DEMOGRAPHICS request from a macro. If you execute a macro that contains a COLLECT DEMOGRAPHICS request, the database aborts the request and returns an error.