Conventions Used in This Book

The following typographical conventions are used in this book:


Used for emphasis, for the first use of a technical term, for example URLs, and for file and directory names.

Constant width

Used for SQL examples, file contents, and examples of output.


Used for table and column names, whether in SQL or referring to SQL from within the body of a paragraph. Also used for alias names and node names, which are elements in a SQL diagram that theoretically refer to table aliases, even when a diagram sometimes shows an abstract tuning problem without referring to a specific SQL statement that corresponds to that problem. Since aliases are usually made an acronym based on a table name, such as CT for the column Code_Translations, aliases are usually pure uppercase.

(C, O, OT, OD, ODT, P, S, A)

A constant-width list of aliases, node names, or columns, bounded in parentheses. I borrow this n-tuple notation from mathematics to indicate an ordered list of items. In the example case, the notation describes a join order between nodes in a join diagram, representing table aliases. In another example, (Code_Type, Code) would represent a pair of indexed columns in a two-column index, with Code_Type as the first column. Alternately, Code_Translations(Code_Type, Code) represents the same index, while specifying that it is on the table Code_Translations.


Constant-width italic text inside angle brackets describes missing portions of a SQL statement template, which you must fill in, that represents a whole class of statements. For example, SomeAlias.Leading_Indexed_Column=<Expression> represents any equality condition matching the leading column of an index with any other expression.


In SQL, uppercase indicates keywords, function names, and tables or views pre-defined by the database vendor (such as Oracle's PLAN_TABLE).

Pay special attention to notes set apart from the text with the following icons:

Indicates a general note, tip, or suggestion. For example, I sometimes use notes for asides specific to a particular database vendor, in the midst of an otherwise vendor-independent discussion.

Indicates a warning, used to point out special pitfalls I've seen relating to the current discussion.