When we create or change tuples, we sometimes do not have values for all components. For instance, we mentioned in "Simple Table Declarations" Example 2 that when we add a column to a relation schema, the existing tuples do not have a known value, and it was

Selection of indexes requires a trade-off by the database designer, and in fact, this choice is one of the principal factors that influence whether a database design is acceptable. Two important factors to examine are:

Relations that are defined with a CREATE TABLE statement in fact exist in the database. That is an SQL system stores tables in some physical organization. They are persistent, in the sense that they can be expected to exist indefinitely and not to change unless they are clearly told to

In limited conditions it is possible to carry out an insertion, deletion, or update to a view. In the beginning, this idea makes no sense at all, since the view does not exist the way a base table (stored relation) does. What could it mean, say, to insert a new tuple into a view? Where