int es_mba_addformula( struct es_mba *agg, const char *formuladefn, char *errbuf, unsigned errbufsize );
Create an algebraic formula to be used to filter-out rows in the query plan.
Formula construction follows the same rules as es_mba_addformula() with the difference that the formula must yield an integer result. A formula result of zero indicates that a row of data should not be incorporated in the aggregate result.
For example, a formula to filter for all sales made in 2007 might look something like:
struct es_mba *agg; char errbuf; es_mba_addfilter( agg, "getyear(SaleDate)==2007", errbuf, 1024 );
|Copyright © 2012 by Richard Brooks|