Throughout this book, syntax is described using the structure defined as follows:
Read the syntax diagrams from left to right and top to bottom, following the path of the line.
The >>--- symbol indicates the beginning of a statement.
The ---> symbol indicates that the statement syntax is continued on the next line.
The >--- symbol indicates that a statement is continued from the previous line.
The -->< symbol indicates the end of a statement.
Required items appear on the horizontal line (the main path).
>>-STATEMENT--required item------------------------------------><
Optional items appear below the main path.
>>-STATEMENT----+----------------+-----------------------------><
'-optional item--'
If an optional item appears above the main path, that item has no effect on the execution of the statement and is used only for readability.
.-optional item--.
>>-STATEMENT----+----------------+-----------------------------><
If you can choose from two or more items, they appear in a stack.
If you must choose one of the items, one item of the stack appears on the main path.
>>-STATEMENT----+-required choice1-+---------------------------><
'-required choice2-'
If choosing none of the items is an option, the entire stack appears below the main path.
>>-STATEMENT----+------------------+---------------------------><
+-optional choice1-+
'-optional choice2-'
If one of the items is the default, it will appear above the main path and the remaining choices will be shown below.
.-default choice--.
>>-STATEMENT----+-----------------+----------------------------><
+-optional choice-+
'-optional choice-'
An arrow returning to the left, above the main line, indicates an item that can be repeated. In this case, repeated items must be separated by one or more blanks.
.--------------------.
V |
>>-STATEMENT-------repeatable item---+-------------------------><
If the repeat arrow contains a comma, you must separate repeated items with a comma.
.-,------------------.
V |
>>-STATEMENT-------repeatable item---+-------------------------><
A repeat arrow above a stack indicates that you can make more than one choice from the stacked items or repeat a single choice.
Keywords appear in uppercase (for example, FROM). They must be spelled exactly as shown. Variables appear in lowercase (for example, column-name). They represent user-supplied names or values in the syntax.
If punctuation marks, parentheses, arithmetic operators, or other such symbols are shown, you must enter them as part of the syntax.
Sometimes a single variable represents a set of several parameters. For example, in the following diagram, the variable parameter-block can be replaced by any of the interpretations of the diagram that is headed parameter-block:
>>-STATEMENT----| parameter-block |----------------------------><
parameter-block
|--+-parameter1-----------------+-------------------------------|
'-parameter2--+-parameter3-+-'
'-parameter4-'
Adjacent segments occurring between "large bullets" (*) may be specified in any sequence.
>>-STATEMENT--item1--*--item2--*--item3--*--item4--------------><
The above diagram shows that item2 and item3 may be specified in either order. Both of the following are valid:
STATEMENT item1 item2 item3 item4 STATEMENT item1 item3 item2 item4