Key to Syntax Diagrams
A word bounded by diagram lines must be separated from adjoining words by at least one separator.
A separator is represented by a white-space character.
Words separated from each other by at least one space in the syntax diagram must also be separated from each other by at least one separator in the real statement.
Where the descriptive names for identifiers used in the diagrams consist of more than one word, these are bound together by hyphens.
Branched lines indicate alternative constructions. Only one branch may be followed for any one passage along the line: in this example either
option-2may be used, but not both.
This representation is used to show that a section of the syntax construction may be repeated. Any construction required between the repetitions is shown on the repeat line.
In this example, the statement must contain at least one instance of
parameter. If several instances are given, they must be separated from each other by a comma. If a comma or other separator is specified in a list, white spaces need not be used between the elements of the list.
Arrows at the beginning and end of a statement show that the statement is complete.
Dots at the beginning or end of a line in a diagram show that the statement on the line is incomplete.
The continuation may be in the same diagram or relate to a separate diagram, as in the language elements, see Operators and Values. The dots are not part of the statement syntax.
Keywords are words that are defined in the SQL language. Keywords are written in
UPPERCASEin the diagrams. They must always be written in the statement exactly as shown, except that the case of letters is not significant.
Examples of keywords are:ALTER CREATE NULL TABLE
Spaces between keywords are significant. Thus the keywords
CREATE TABLEin this example must be separated by at least one white space character.
Parameters are indicated by words in lowercase in the diagrams, and replaced by the appropriate identifiers or constructions when statements are written. Examples of parameters are:column-name expression data-type
The blank spaces in the diagrams are significant. Words bound together by hyphens (e.g.
data-type) represent single parameters.
Syntax Diagram Example
The following sample illustrates the use of the syntax diagrams.
Some valid formulations are:KEYWORD-1 (parameter) option-1 KEYWORD-2 string KEYWORD-1 (parameter, parameter) option-1 KEYWORD-2 string option-3 KEYWORD-1 (parameter, parameter, parameter) option-2 KEYWORD-2 string
The following formulations are not valid:KEYWORD-1 (parameter) KEYWORD-2 string
option-2missingKEYWORD-1 parameter option-1 KEYWORD-2 string
parentheses missingKEYWORD-1 (parameter,) parameter option-2 KEYWORD-2 string
closing parentheses wrongly placedKEYWORD-1 (parameter, parameter) option-1KEYWORD-2 stringoption-3
separating blanks missingKEYWORD-1 (parameter parameter parameter) option-2 KEYWORD-2 string
no commas in parameter list
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