COLLECT DEMOGRAPHICS
Purpose
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.
Syntax
where:
|
Syntax element … |
Specifies … |
|
database_name user_name |
the containing database or user for table_name if something different from the current database or user. |
|
table_name |
the names of tables for which data demographic estimates are to be collected. |
|
QCD_name |
the name of the QCD database into which the collected data demographic estimates are to be written. |
|
ALL |
to collect both primary and index subtable data demographic estimates. This is the default. |
|
WITH NO INDEX |
to exclude index subtable data demographic estimates from the collection and collect only primary data estimates. |
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:
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 on an AMP-wise basis into the DataDemographics table of the specified query capture database. 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 SQL Request and Transaction Processing.
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:
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, Teradata Database aborts the request and returns an error.
Example
Collect demographic estimates on table_1 in database db_1 and write the results into the DataDemographics table of user-defined QCD MyQCD.
COLLECT DEMOGRAPHICS FOR db_1.table_1 INTO MyQCD;
Example
An entry already exists in the DataDemographics table for the specified table, then it is updated with the currently collected demographic estimates. The value of TimeStamp is updated to reflect the current time.
COLLECT DEMOGRAPHICS FOR db_1.table_1 INTO MyQCD; /* Inserts data
into DataDemographics table of MyQCD */
COLLECT DEMOGRAPHICS FOR db_1.table_1 INTO MyQCD; /* Updates data
in DataDemographics table of MyQCD */
For More Information
For more information about index analysis, see: