Limitations on use of strings

The following varying-length string data types cannot be referenced in certain contexts:

Table 4. Contexts for limitations on use of varying-length strings
Context of usage LOB (CLOB, DBCLOB, or BLOB)
A GROUP BY clause Not allowed
An ORDER BY clause Not allowed
A CREATE INDEX statement Not allowed
A SELECT DISTINCT statement Not allowed
A subselect of a UNION, EXCEPT, or INTERSECT without the ALL keyword Not allowed
The definition of primary, unique, and foreign keys Not allowed
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 CLOB or DBCLOB strings, or both as input. See the description of the individual functions in Built-in functions for the data types that are allowed as input to each function.