Netezza uses a cost-based optimizer to determine the best method for scan and join operations, join order, and data movement between SPUs, that is, redistribute or broadcast operations. You can use the Netezza EXPLAIN command to display the actual execution plan that Netezza generates and uses while executing any query in the system. Netezza Optimizer Netezza uses the cost based optimizer to determine the best methods for the query to be executed in the Netezza system. Optimizer uses the statistics to determine the optimal and best execution plan for Netezza…

Netezza data warehouse appliance does soft delete until the groom process is performed. Netezza logically deletes the rows by flagging deletexid. The data will be there in the system and you can recover the same whenever you accidentally delete the rows from the table. In this article, We will check how to perform Netezza recover deleted rows. Netezza Recover Deleted Rows Every table has the system columns such as createxid, deletexid and rowid. You can check the column by querying these columns from the table. Whenever you delete the record…

The Netezza rollup functionality gives aggregation results at multiple grouping levels in a single result set. In this article, we will check Netezza rollup group aggregates using grouping sets. Netezza Rollup Group Aggregates using Grouping sets You may want to aggregate the records in the tables for each records partition in the group. For examples, consider you want to find out sum of salary of the all employees in the department as a different rows in the query result (row with NULL employee name as highlighted in the image). To…

When you create a table in IBM Netezza, the table usually does not take any space on the data slices. Once you insert the rows then only system allocates the space to the rows. In this article, we will see the Netezza table row size details and what are the system columns and their size when you insert rows into the created table. Netezza Table Row Size Details When you insert new row to the created table, IBM Netezza system allocates at least one extent of size 3 MB of…

Life is much easier if you use any query tools to access Netezza nzsql queries. Some people do not like to use specific tool, instead they use Netezza command line. In this article, we will check on Netezza nzsql Query Buffer to edit command line Queries. Netezza nzsql Query Buffer Because the nzsql command is line oriented, it is difficult to edit a complex, multiline SQL statement. Netezza sql supports query buffer that you can use to edit complex and multiline queries. Netezza nzsql Query Buffer Options \e — Edit…

When you use the Netezza nzsql command in interactive mode, there are many options that you can use. These options, known as Netezza nzsql internal slash options, are called with a backslash (\). Many of the internal slash options are the same as those available on the command line. In this article, we will check some of commonly used Netezza nzsql Internal Slash Options. Netezza nzsql Internal Slash Options Following are some commonly used Netezza nzsql internal slash commands: Command Description \? Lists the available internal slash commands. \h Lists…