unequal join

A join based on the inequality of the joined fields. The inequality operator can be either the greater than ">", the less than "<", the greater than or equal to ">=", the less than or equal to "<=", or the not equal to "<>" symbol.

union query

A single query that combines the resultant records of two or more select queries.

unique index

An index whose key fields contain unique values for each record of the table.

update query

An action query that will modify the field values of a record or group of records in a table.

upsize

The migration of data from one data format to another with the premise that the destination format is more robust or diverse than the original format.

user interface (UI)

The application that allows people to interact with the data; it is primarily comprised of forms and reports.

user-defined function (UDF)

Aprocedure or function created to return a result or perform a sequence of tasks.

validation of data

The process of ensuring that a program accepts and uses clean, correct, and useful data.

value list

A fixed list of values that are provided in the field properties as the row source for combo box and list box controls in Access. Although some updates can be managed through the UI, value lists are best for short, static lists.

work table

See temporary table.

XML schema definition (XSD)

Formally describes the elements in an Extensible Markup Language (XML) document. This description can be used to verify that the information in an XML document adheres to the expectations of the data.

zero-length strings (ZLS)

A string value that intentionally has no characters; but it is a known value. Often called a ZLS or an empty string, it isrepresented by a set of double quotes with nothing between " ". The ZLS can be contrasted with a Null value, which is an unknown value with no apparent data.