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: Restrictions using long strings : A long string has one of the following varying-length string data types: : : For character strings. A VARCHAR string with a maximum length that is greater than 255 bytes or any CLOB string. : For graphic strings. A VARGRAPHIC string with a maximum length that is greater than 127 characters or any DBCLOB string. : For binary strings. Any BLOB string. : Table 3 indicates the contexts in which long strings cannot be referenced. The restrictions differ slightly for long strings with LOB data types (CLOB, DBCLOB, and BLOB). : : Table 3. Contexts in which long strings cannot be referenced : : Context of usage : VARCHAR (>255) or VARGRAPHIC (>127) : LOB (CLOB, DBCLOB, or BLOB) : : A GROUP BY clause : Not allowed : Not allowed : : An ORDER BY clause : Not allowed : Not allowed : : A CREATE INDEX statement : Not allowed : Not allowed : : A SELECT DISTINCT statement : Not allowed : Not allowed : : A subselect of a UNION without the ALL keyword : Not allowed : Not allowed : : A host variable in a EXECUTE IMMEDIATE or a PREPARE statement : -- : Not allowed : : Predicates : Cannot be used in any predicate except EXISTS and LIKE. This restriction includes a simple-when-clause in a CASE expression. expression WHEN expression in a simple-when-clause is equivalent to a predicate with expression=expression. : Cannot be used in any predicate except EXISTS, LIKE, and NULL. This restriction includes a simple-when-clause in a CASE expression. expression WHEN expression in a simple-when-clause is equivalent to a predicate with expression=expression. : : The definition of primary, unique, and foreign keys : Not allowed : Not allowed : : Check constraints : -- : Cannot be specified for a LOB column : : Field procedure : -- : Cannot be specified for a LOB column. : : Parameters of built-in functions : Some functions that allow varying-length character strings, varying-length graphic strings, or both types of strings as input arguments do not support VARCHAR or VARGRAPHIC long strings, CLOB or DBCLOB strings, or both as input. See the description of the individual functions in "Chapter 3. Functions" in topic 3.0 for the data types that are allowed as input to each function. : : Distributed data applications : -- : LOB columns cannot be used if remote access is performed with DB2 private protocol access. :

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