#### SQL database considerations

Since indexes are not critical with SQL data, the primary concern with both linked tables and subreports is whether or not there is a selection formula in the primary report that puts range limits on Table A. See Linking data files.

##### Linked SQL tables

If there are range limit conditions in the selection formula, the program passes those conditions down to the server.

- If there is a selection formula that puts range limits on Table A, the server locates the records in Table A that satisfy the selection criteria (2), matches them up with the appropriate records in Table B (100), and returns 200 merged records to the Report Engine.
- If there is no selection formula, or if there is a selection formula that does not put range limits on Table A, the server matches up each record in Table A (26) with the appropriate records in Table B (100), and returns 2600 merged records to the Report Engine.

In either case, the Report Engine will then apply the entire selection formula to the merged records.

##### Subreports and SQL databases

If you are creating a primary report based on Table A and a subreport based on Table B:

- The number of subreports that are run is determined by the selection formula situation in the primary report.
  - If there is a selection formula and it passes down range limits on Table A, the program runs a subreport only for those records that satisfy range limit conditions (2).
  - If there is no selection formula, or if the selection formula does not pass down range limits on Table A, the program runs a subreport for every record in Table A (26).
- The number of records read by each subreport remains the same regardless of whether there was range limit selection on Table A. Each subreport will read only those records in Table B that match each record read in Table A (100).

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