Conventions Used in This Book

I use a number of typographical and coding conventions in this book. Take time to become familiar with them. Doing so will enhance your understanding of the text. Coding conventions in particular are important, because I can't discuss them anew for each recipe in the book. Instead, I list the important conventions here.

Typographical Conventions

The following typographical conventions are used in this book:

UPPERCASE

Used to indicate SQL keywords within text

lowercase

Used for all queries in code examples. Other languages such as C and JAVA use lowercase for most keywords and I find it infinitely more readable than uppercase. Thus all queries will be lowercase.

Constant width bold

Indicates user input in examples showing an interaction.

Indicates a tip, suggestion, or general note.

Indicates a warning or caution.

Coding Conventions

My preference for case in SQL statements is to always use lowercase, for both keywords and user-specified identifiers. For example:

 select empno, ename   from emp; 

Your preference may be otherwise. For example, many prefer to uppercase SQL keywords. Use whatever coding style you prefer, or whatever your project requires.

Despite my use of lowercase in code examples, I consistently uppercase SQL keywords and identifiers in the text. I do this to make those items stand out as something other than regular prose. For example:

The preceding query represents a SELECT against the EMP table.

While this book covers databases from five different vendors, I've decided to use one format for all the output:

  EMPNO ENAME  ----- ------   7369 SMITH   7499 ALLEN … 

Many solutions make use of inline views, or subqueries in the FROM clause. The ANSI SQL standard requires that such views be given table aliases. (Oracle is the only vendor that lets you get away without specifying such aliases.) Thus, my solutions use aliases such as x and y to identify the result sets from inline views:

 select job, sal   from (select job, max(sal) sal           from emp         group by job) x; 

Notice the letter X following the final, closing parenthesis. That letter X becomes the name of the "table" returned by the subquery in the FROM clause. While column aliases are a valuable tool for writing self-documenting code, aliases on inline views (for most recipes in this book) are simply formalities. They are typically given trivial names such as X, Y, Z, TMP1, and TMP2. In cases where I feel a better alias will provide more understanding, I do so.

You will notice that the SQL in the SOLUTION section of the recipes is typically numbered, for example:

 1 select ename 2     from emp 3  where deptno = 10 

The number is not part of the syntax; I have included it so I can reference parts of the query by number in the discussion section.