DROP STATISTICS (QCD Form)
Purpose
Drops sampled statistics on the specified table from the TableStatistics table in the specified QCD_name.
Syntax
where:
|
Syntax Element … |
Specifies … |
|
FROM QCD_name |
the name of the QCD database from which statistics on the specified table columns and indexes are to be dropped from the TableStatistics table. |
|
database_name | user_name |
the name of the containing database or user for table_name if different from the current database or user. |
|
table_name |
the name of the table for which sampled column and index statistics are to be dropped. |
|
COLUMN column_name |
the set of non-indexed columns for which sampled statistics are to be dropped. You cannot drop statistics on a UDT column. |
|
COLUMN PARTITION |
that statistics are to be dropped on the system‑derived PARTITION column for a PPI table. You cannot reference the PARTITION#Ln columns of a PPI table in a DROP STATISTICS request. See “Collecting QCD Statistics on the PARTITION Column of a PPI Table” on page 560 for more information about the PARTITION column. |
|
INDEX index_name |
the name of the index for which sampled statistics are to be dropped. |
|
INDEX column_name |
the column set for which sampled statistics are to be dropped. |
ANSI Compliance
DROP STATISTICS (QCD Form) is a Teradata extension to the ANSI SQL:2011 standard.
Required Privileges
You must have the following privileges to perform DROP STATISTICS (QCD Form):
Invocation
Normally invoked using client‑based database query analysis tools.
Difference Between DROP STATISTICS (QCD Form) and DROP STATISTICS (Optimizer Form)
Unlike the DROP STATISTICS (Optimizer Form) statement, DROP STATISTICS (QCD Form) does not drop the statistics kept in the data dictionary for use by the Optimizer. The DROP STATISTICS (QCD Form) drops statistics from the TableStatistics table of the specified QCD database.
DROP STATISTICS (QCD Form) and INSERT EXPLAIN WITH STATISTICS
DROP STATISTICS (QCD Form) does not drop statistics from the QCD that were captured using an INSERT EXPLAIN WITH STATISTICS request. These statistics are dropped automatically whenever their corresponding query plan is deleted from the QCD.
DROP STATISTICS (QCD Form) and Transaction Processing
You can place a DROP STATISTICS (QCD Form) request anywhere within a transaction because it is not treated as a DDL statement by the Transaction Manager.
Dropping Statistics On UDTs
You cannot DROP STATISTICS on a UDT column.
Example
The following example drops statistics on all columns and indexes for the orders table from the TableStatistics table of the QCD database named MyQCD.
DROP STATISTICS FROM MyQCD
ON orders;
Example
The following example drops statistics on a single‑column NUSI named orderDateNUPI from the TableStatistics table of the QCD database named MyQCD.
DROP STATISTICS FROM MyQCD
ON orders INDEX orderDateNUPI;
Example : Dropping PARTITION Statistics
The following DROP STATISTICS request drops statistics on the PARTITION column only for the PPI table named table_1 from the TableStatistics table in the QCD named QCD_11:
DROP STATISTICS FROM QCD_11 ON table_1
COLUMN PARTITION;
The following DROP STATISTICS request drops statistics on the column named column_1 and the system‑derived PARTITION column for the PPI table named table_2 from the TableStatistics table in the QCD named QCD_12:
DROP STATISTICS FROM QCD_12 ON table_2
COLUMN (column_1, PARTITION);
The following table-level DROP STATISTICS request drops all the statistics, including statistics on the system‑derived PARTITION column, for the PPI table named table_3 from the TableStatistics table in the QCD named QCD_13:
DROP STATISTICS FROM QCD_13 ON table_3;
For More Information
See these related statements for more information: