Character string constants

A character string constant specifies a varying-length character string. There are two forms of character string constant.

• A sequence of characters that starts and ends with a string delimiter, which is either an apostrophe (') or a quotation mark ("). For the factors that determine which is applicable, see Apostrophes and quotation marks as string delimiters. This form of string constant specifies the character string contained between the string delimiters. The number of bytes between the delimiters must not be greater than 32704. The limit of 32704 refers to the length (in bytes) of the UTF-8 representation of the string. If you produced the string in a CCSID other than UTF-8 (for example, an EBCDIC CCSID), the length of the UTF-8 representation might differ from the length of the string's representation in the source CCSID. Two consecutive string delimiters are used to represent one string delimiter within the character string.
• An X followed by a sequence of characters that starts and ends with a string delimiter. This form of a character string constant is also called a hexadecimal constant. The characters between the string delimiters must be an even number of hexadecimal digits. The number of hexadecimal digits must not exceed 32704. A hexadecimal digit is a digit or any of the letters A through F. If the MIXED DATA subsystem parameter is set to YES, hexadecimal digits in a hexadecimal constant must be specified in upper case. Otherwise, an error might be returned when SQL statements are processed. Under the conventions of hexadecimal notation, each pair of hexadecimal digits represents a character. A hexadecimal constant allows you to specify characters that do not have a keyboard representation.

'12/14/1985'    '32'    'DON''T CHANGE'    X'FFFF'    ''

The right most string in the example ('') represents an empty character string constant, which is a string of zero length.

A character string constant is classified as mixed data if it includes a DBCS substring. In all other cases, a character string constant is classified as SBCS data. For information about the CCSID that is assigned to the constant, see Determining the encoding scheme and CCSID of a string. A mixed string constant can be continued from one line to the next only if the break occurs between single byte characters. A Unicode string is always considered mixed regardless of the content of the string.

For Unicode, character constants can be assigned to UTF-8 and UTF-16. The form of the constant does not matter. Typically, character string constants are used only with character strings, but they also can be used with graphic UTF-16 data. However, hexadecimal constants are just character data. Thus, hexadecimal constants being used to insert data into UTF-16 data strings should be in UTF-8 format, not UTF-16 format. For example, if you wanted to insert the number 1 into a UTF-16 column, you would use X'31', not X'0031'. Even though X'0031' is a UTF-16 value, DB2 treats it as two separate UTF-8 code points. Thus, X'0031' would become X'00000031'.