SEARCH_CONDITION is LONG so you can't use it for .... very much useful.
For this particular use, I suggest PLSQL routine to write the LONG col into a VARCHAR2(32767) and then apply the check on teh VARCHAR2 variable.
LONGs are an absolute pain.
Also, in your case you can restrict the dataset further by querying ALL_CONS_COLUMNS WHERE column_name = 'colname' and joining the ALL_CONSTRAINTS to get the SERACH_CONDITION.
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