Filtering is typically done by comparing at least one field with some criterion value or expression. The comparison operators include those discussed for comparison in Excel s IF function. For such purpose, it s useful to note that there is such a thing as a null string . For example, suppose we wish to query the database for the names of all our foreign students. Recall that we have not filled anything into the Country field of a US address.
Text has order, closely related to alphabetical order.
Suppose we wish to select the records of all students with last initial between N and R, inclusively. Suppose we wish to select the records of those students, and only those students, who have out-state addresses or unpaid bills or are in Academic Exploration. Note in particular that we may use a previously designed query as the data source for another query.