In this book, syntax for some commands is presented in syntax diagrams. This section shows some of the structures contained in these diagrams.
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 or command.
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.
Diagrams of syntactical units that are not complete statements start with the >--- symbol and end with the ---> symbol.
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, it can be added for improved readability of the statement but it has no effect on the statement's execution.
+-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, CREATE TABLE). 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.