July 2010
Intermediate to advanced
840 pages
16h 33m
English
Content preview from Joe Celko's SQL for Smarties, 3rd Edition
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Chapter 11. CASE Expressions
THE CASE EXPRESSION IS probably the most useful addition in SQL-92. This is a quick overview of how to use the expression, but you will find other tricks spread throughout the book.
The reason it is so important is that:
| 1. | It works with any data type. |
| 2. | It allows the programmer to avoid procedural code by replacing IF-THEN-ELSE control flow with CASE expression inside the query. |
| 3. | It makes SQL statements equivalent to primitive recursive functions. You can look up what that means in a book on the theory of computation, but it is a nice mathematical property that guarantees certain kinds of problems can be solved. |
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