USE THE EXISTS CLAUSE WITH SELECT *

Although it isn't a standard that the EXISTS clause must be used with
"SELECT *" statements, it's a good practice to follow. The primary reason
is that the recipient of the result set may have a static structure in
which to hold the result set. If the underlying table(s) and/or view(s) have
columns added or deleted, the recipient of the result set will have
failed to account for the change. Another consideration is that the impact of
modifying code that contains a large number of "SELECT *" statements can
be significant. This adds to the maintenance and design considerations
for new or enhanced functionality within the system that the database
supports.

Reducing the SELECT statement's columns to just those that are needed
may improve performance. The best approach is to always use qualified SQL
statements. This includes INSERT statements. Even if the recipient of the
result set has a dynamic structure in which to hold the result set, it is
easier to read and maintain the code if qualified SQL statements are
used.