Last Returns the last value. Where Allows criteria to be established for queriesperforming calculations. Some functions work with specific data types. For example, you can use Sum with number and currency fields but not with OLE object or memo fields. To tell Access to carry out one of these functions on the data in a table, you open a Query window, click the Totals button on the toolbar to add a new Total row to the QBE grid, and then indicate the function you want to use in the appropriate column.
Access puts the result in a new field in the query datasheet.
Count, Avg, and Sum. Close any open Select Query windows without saving the queries, and open a new query for the Invoices and Clients table. Double-click the OrganizationName field to add it to the QBE grid, and then click the Totals button on the toolbar. Group By in the Size column of this row, meaning that by default it will simply group the records in the Estimates table by size. Click in the Total row and enter sum using the drop-down menue .