use the function_based index to access the null value
select .... from ... where lxr is null;
this statement can't use the idnex!!!
grant query rewrite to scott;
alter system set query_rewrite_enabled=true; --the default is false
alter system set query_rewrite_integrity=trusted; -- the default is enforced
create index idx_c_khxx_zb_lxr on c_khxx_zb(case when lxr is null then 1 end);
-- alter the index created, gather the table's stats
begin
dbms_stats.gather_table_stats(user,'C_KHXX_ZB',cascade=>true);
end;
/
set autotrace traceonly explain (if not , system @rdbms/admin/utlxplan.sql)
select * from emp.......
set autotrace off
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