An array is a list of values grouped into a single value. An array may be of variable length; in one record the array field may contain two elements, while in the next record, it contains six elements. 



Ragged arrays: The above arrays are collectively a set of ragged arrays. The number of elements in each array varies. When arrays are ragged, some array functions may return null or empty values.

Nested arrays: The last example above is a nested array, in which one array is nested inside of another.