How to read the syntax diagrams
This topic describes the structure of SQL syntax diagrams.
Read the syntax diagrams from left to right and top to bottom, following the path of the line.
Two right arrowheads and a line ►►── indicates the beginning of a syntax diagram.
A line and a single right arrowhead ──► indicates that the syntax is continued on the next line.
A right arrowhead and a line ►── indicates that the syntax is continued from the previous line.
A line followed by a right arrowhead and a left arrowhead ──►◄ indicates the end of a syntax diagram.
Syntax fragments start with a vertical bar and hyphens |── and end with hyphens and a vertical bar ──|.
Required items appear on the horizontal line (the main path).
Optional items appear below the main path.
If an optional item appears above the main path, that item has no effect on execution, and is used only for readability.
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.
If choosing one of the items is optional, the entire stack appears below the main path.
If one of the items is the default, it will appear above the main path, and the remaining choices will be shown below.
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.
If the repeat arrow contains a comma, you must separate repeated items with a comma.
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,
They must be spelled exactly as shown. Variables appear in lowercase
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 larger fragment
of the syntax. For example, in the following diagram, the variable
the whole syntax fragment that is labeled parameter-block:
Adjacent segments occurring between
large bullets (●)
may be specified in any sequence.
required_item item1 item2 item3 item4 required_item item1 item3 item2 item4