As a result of the execution of this directive, an initial amount of space is reserved in secondary memory to accommodate future values of the tabular variable, and the metadata are modified to reflect the addition of the new tabular variable. Specialized SQL constructions, discussed later (insert, delete, and update) can be used to modify the value of this variable. Creation of tabular variables permits placing restrictions, called constraints on the contents of any value that the tabular variable may assume. The constraints that follow have a global character (which means that they apply to the contents of a table in its entirety) and apply to any value that the tabular variable may assume.