how to find constraints on a table in oracle
SELECT cons.OWNER AS CHILD_OWNER,
cons.TABLE_NAME AS CHILD_TABLE,
cons.CONSTRAINT_NAME AS CONSTAINT_NAME,
cons.CONSTRAINT_TYPE AS CONSTRAINT_TYPE,
col.OWNER AS PARENT_OWNER,
col.TABLE_NAME AS PARENT_TABLE,
col.COLUMN_NAME AS COLUMN_NAME
FROM DBA_CONS_COLUMNS col, DBA_CONSTRAINTS cons
WHERE cons.R_OWNER = col.OWNER
AND cons.R_CONSTRAINT_NAME = col.CONSTRAINT_NAME
AND cons.TABLE_NAME = 'table_name';