Abstract
This chapter delineates the importance of unlearning the procedural thinking and moves to a pure SQL view. Programmers tend to make the same kinds of errors in their designs and their code over and over. They confuse RDBMS with the file systems and 3GL- or OO-oriented programming environments they first learned. Programmers from the C family of languages tend to put the entire program in lowercase as if they were still using a teletype on a UNIX system. Mainframe programmers tend to put the entire program in uppercase as if they were still using punch cards or a 3270 video monitor for input. Cohesion is how well a module of code does one and only one thing, that it is logically coherent. There are several types of cohesion. The original definitions have been extended from procedural code to include OO and class hierarchies. The symptom in DDL is a table with lots of NULL-able columns. It is probably two or more entities crammed into a single table. The symptom in DML is a query or other statement that tries to do too many things. When the same procedure or query checks inventory and build a personnel report, cohesion problems crop up. The table-valued function shows that the programmer still wants to see procedural coding complete with parameters. An SQL programmer would think in terms of VIEWS and CTES.
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