How to read the syntax diagrams 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 bP-required item-repeatable it 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, FROM). They must be spelled exactly as shown. Variables appear in lowercase(for example, col umn-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 parameter-block represents he whole syntax fragment that is labeled parameter-block -required item- parameter-block parameter-block Adjacent segments occurring between"large bullets"(O)may be specified in required item-ttem1-●ttem2-●ttem3-●tem4 The above diagram shows that item2 and item3 may be specified in either order. Both of the following are validAn 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.

required_item  repeatable_item
If the repeat arrow contains a comma, you must separate repeated items with a comma.

required_item  , 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 larger fragment of the syntax. For example, in the following diagram, the variable parameter-block represents the whole syntax fragment that is labeled parameter-block:

required_item parameter-block
parameter-block: parameter1 parameter2 parameter3 parameter4 Adjacent segments occurring between “large bullets” (*) may be specified in any sequence.

required_item item1 * item2 * item3 * item4
The above diagram shows that item2 and item3 may be specified in either order. Both of the following are valid: How to read the syntax diagrams x SQL Reference, Volume 2