This section covers two related but subtly different topics: Unique Values and Duplication in data.
In particular, this section is organized as follows:
Unique Values: We cover how to identify
unique values, count unique values, and compute the frequency and proportion of occurrence of each
unique value. We look at scenarios involving a single column and scenarios involving the unique
combinations of a set of columns of a table.
Duplicates: We cover how to identify,
count, return, and drop duplicate values. The focus is on duplication among rows in a table where
a duplicate may be defined as the values of all or a subset of columns being equal among
multiple rows.