查询一个表的主键名称
select  *
  from dba_constraints t
  where t.table_name =upper('dl_cjhb')
      and t.constraint_type='P'
查询表的主键对应的字段列表
select  tt.column_name
  from dba_constraints t, dba_ind_columns tt
  where t.table_name =upper('dl_cjhb')
      and tt.table_name=t.table_name
      and t.constraint_type='P'
      and t.index_name = tt.index_name
dba_cons_columns
OWNER                          CONSTRAINT_NAME                CONSTRAINT_TYPE TABLE_NAME                     SEARCH_CONDITION                                                                 R_OWNER                        R_CONSTRAINT_NAME              DELETE_RULE STATUS   DEFERRABLE     DEFERRED  VALIDATED     GENERATED      BAD RELY LAST_CHANGE INDEX_OWNER                    INDEX_NAME                     INVALID VIEW_RELATED
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