What are some of the problems with arrays or repeated groups in a database?

What will be an ideal response?

When there is an array or a repeated group in a database entity, it is difficult to retrieve data. With an array, the only way to retrieve a specific value from the column is to use some sort of string function to extract it from the list. With a repeated group, the user has no idea which column of the group will contain the value he or she wants, so they will have to query all the columns in the group. Groups also lack flexibility. Say you have three columns in a group. If there are only two values then one of the columns must remain null; if there are four values, there is nowhere to store the fourth one.