CODD: Well, a couple of things. Before I moved out to San Jose in ’68, I attended a talk in Poughkeepsie given by a small software firm from Los Angeles, and they were describing the firm’s DBMS. Now, in predicate logic, the two main quantifiers are the existential and the universal. I asked him to what extent the product - 30 - supported the existential quantifier. ” So right there, I knew that he didn’t know a damn thing about predicate logic. DBMS: I guess for him it wasn’t an an [sic] intuitive leap to connect predicate logic to the management of data.

In this case, you are depending on the indexing method to allow the first part of the index, the last name, to be searched so that the first name will be brought along with it. 4 Hashing Functions Hashing functions take a very different approach to finding data. These functions take the value of the column(s) used in the search and convert them into a number that maps into an address in physical data storage. ), which has the actual disk address in it. The disk drive can then be positioned directly to that physical address and read the data.

A UNIQUE or PRIMARY KEY constraint) in the base table. 3. All columns not shown in the VIEW must have default values or be NULLable (if you think about it for a minute, this lets you construct and insert a complete row into the base table). - 47 - The whole idea is that an updatable VIEW looks and behaves pretty much like a base table, but slightly restricted as to what you can see. One row in the VIEW maps to exactly one row in the base table from which it is drawn. However, other views are updatable, and some vendors support more than the basic version given in the SQL-92 standard.