Appendix C: Syntax Conventions

Syntax diagrams in this book use Backus-Naur Form syntax notation conventions. Backus-Naur Form has become the de facto standard for most computer texts :

• Angle brackets:  < ... >. Angle brackets are used to represent names of categories and are also known as substitution variable representation . In this example, <table> will be replaced with a table name :

     SELECT * FROM <table>;   

  The preceding code becomes:

     SELECT * FROM country;   

• OR:  . A pipe or character represents an OR conjunction meaning either can be selected. In this case, all or some fields can be retrieved, some meaning one or more:

     SELECT { *  { <field>, ... } } FROM <table>;   

  The preceding code becomes:

     SELECT name, id, population FROM country;   

• Optional:  [ ]. In a SELECT statement, a WHERE clause is syntactically optional:

     SELECT * FROM <table> [ WHERE <field> = ... ];   

  The preceding code becomes:

     SELECT * FROM name WHERE name='England';   

• At least one of:  { }. For example, the SELECT statement must include one of *, or a list of one or more fields:

     SELECT { *  { <field>, ... } } FROM <table>;   

  The preceding code becomes:

     SELECT name, id, population FROM country;   

This is not a precise interpretation of Backus-Naur Form where curly braces usually represent zero or more. In this book, curly braces represent one or more iterations, never zero.