A family of Microsoft relational database management systems designed for ease of use.
Click Query Design in the Create tab of the ribbon.
Add your table.
Add * from the field list to the query grid.
In the next column, create a calculated field:
Rand: Rnd([FieldName])
where FieldName is the name of a number field in your table (it doesn't matter which, but an AutoNumber field is ideal for this purpose).
Clear the Show check box for this column.
Click in an empty part of the top pane of the query design window.
If necessary, activate the Property Sheet.
Set the Top Values property to 50 (this value is not in the dropdown list, but you can type it yourself).
Each time you "run" the query, it will select 50 records at random.