• A brief introduction that explains the purpose of the statement
• A syntax diagram that shows how to enter the statement correctly
• A syntax table that explains each input parameter in the syntax diagram
• Rules of usage, including examples that illustrate these rules

Each statement description concludes with references to related information in this manual and other manuals.

The major aids for entering SQL statements successfully include:

• the combination of the syntax diagram and syntax table.
• the examples of syntax that appear in the rules of usage.
• the references to related information.

The "Syntax Conventions" section explains the elements that can appear in a syntax diagram and the paths that connect the elements to each other. This section also includes a sample syntax diagram that illustrates the major elements of all syntax diagrams. The narrative that follows the sample diagram shows how to read the diagram in order to enter the statement successfully.

When a syntax diagram within a statement description includes input parameters, the syntax diagram is followed by a syntax table that shows how to enter the parameters without generating errors. Each syntax table includes the following columns:

• The Elements column lists the name of each parameter as it appears in the syntax diagram.
• The Purpose column briefly states the purpose of the parameter. If the parameter has a default value, it is listed in this column.
• The Restrictions column summarizes the restrictions on the parameter, such as acceptable ranges of values.
• The Syntax column refers to the SQL segment that gives the detailed syntax for the parameter.

• To show how to accomplish particular tasks with the statement or its clauses
• To show how to use the syntax of the statement or its clauses in a concrete way

Tip: An efficient way to understand a syntax diagram is to find an example of the syntax and compare it with the keywords and parameters in the syntax diagram. By mapping the concrete elements of the example to the abstract elements of the syntax diagram, you can understand the syntax diagram and use it more effectively.

Using References

The "References" section points to related information in this manual and other manuals that helps you to understand the statement in question. This section provides some or all of the following information:

• The names of related statements that might contain a fuller discussion of topics in this statement
• The titles of other manuals that provide extended discussions of topics in this statement
• The chapters in the Informix Guide to SQL: Tutorial that provide a task-oriented discussion of topics in this statement

Tip: If you do not have extensive knowledge and experience with SQL, the "Informix Guide to SQL: Tutorial" gives you the basic SQL knowledge that you need to understand and use the statement descriptions in this manual.