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Report Builder
User’s Guide


Using the No Join Reorder Option

The SQL Engine in Report Builder checks the SQL in reports to optimize performance. If you are using implicit join syntax for inner joins, the SQL Engine might change the order in which tables are listed in the FROM clause of a SELECT statement during optimization. The hierarchy the SQL Engine uses to reorder the tables might not always produce the best order to query the database.

You can specify that you do not want the tables to be reordered. Choose Database No Join Reorder. The SQL Engine will not reorder the tables in an implicit join. Choosing this option might improve the performance of your reports.

For example, the hierarchy ranks a field that is a unique index as better than a field that is not an index. The SQL Engine would reorder the FROM clause to query the table with the unique index field first. However, if the table with the unique index field contains 500,000 records and the table with the other field contains 30,000 records, the reordered query is less efficient than a query that looks at the smaller table first.

This option does not work if you use the -rbexpjoins startup parameter. The -rbexpjoins startup parameter forces Report Builder to use explicit join syntax for inner joins. See the Progress SQL-89 Guide and Reference for more information on the difference between implicit and explicit joins.


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