Improving update performance
An update is a data manipulation language, or DML operator. Updating a PI column causes performance degradation:
UPDATE table_name SET col_name=expression [, ..., col_name=expression] [ALL | WHERE condition];
Getting ready
For this recipe to complete, you need to connect to the Teradata instance and open SQLA.
How to do it...
- Identify the target table that needs to be updated.
- Identify the source table from which the update is to be done:
update test01.web_clicks a -- Target update table from test02.wed_address b -- Source update table set acc_last_date= date -- Target column that's need to updated where a.Rego_Start_Dt between '2016-12-25' and '2017-01-28' -- Partition column
How it works...
As we understand it, update is used to alter or change the values of existing rows of a table. The updating of the rows can be based on some where condition or full table if needed. You can use sub queries in update statements.
There is much to consider when it comes to updating rows...