Tokens
The basic syntactical units of the SQL language are called tokens. A token consists of one or more characters of which none are blanks, control characters, or characters within a string constant or delimited identifier.
Tokens are classified as ordinary or delimiter tokens:
- An ordinary token is a numeric constant, an ordinary
identifier, a host identifier, or a keyword. Examples:
1 .1 +2 SELECT E 3
- A delimiter token is a string constant, a delimited
identifier, an operator symbol, or any of the special characters shown
in the syntax diagrams. A question mark (?) is also a delimiter token
when it serves as a parameter marker, as explained in PREPARE. Examples:
, 'string' "fld1" = .
Spaces
A space is a sequence of one or more blank characters.
Control characters
A control character is a special character that is used for string alignment. Treated similar to a space, a control character does not cause a particular action to occur. The following table shows the control characters that DB2® recognizes and their hexadecimal values.
Control character | EBCDIC hex value | UTF-8 hex value | UTF-16 hex value |
---|---|---|---|
Tab | 05 | 09 | U+0009 |
Form feed | 0C | 0C | U+000C |
Carriage return | 0D | 0D | U+000D |
New line | 15 | C285 | U+0085 |
Line feed | 25 | 0A | U+000A |
DBCS space | - | - | U+3000 |
Tokens, other than string constants and certain delimited identifiers, must not include a control character or space. A control character or space can follow a token. A delimiter token, control character, or a space must follow every ordinary token. If the syntax does not allow a delimiter token to follow an ordinary token, a control character or a space must follow that ordinary token.
Comments
- simple comments
- Simple comments are introduced with two consecutive hyphens (--). Simple comments cannot continue past the end of the line. For additional information, see SQL comments.
- bracketed comments
- Bracketed comments are introduced with /* and end with */. A bracketed comment can continue past the end of the line. For additional information, see SQL comments.
Uppercase and lowercase
A token in an SQL statement can include lowercase letters, but lowercase letters in an ordinary token are folded to uppercase. However, lowercase letters are folded to uppercase in a C or Java program only if the appropriate precompiler option is specified. Delimiter tokens are never folded to uppercase.
select * from DSN8A10.EMP where lastname = 'Smith';
SELECT * FROM DSN8A10.EMP WHERE LASTNAME = 'Smith';