第一次注意到这样也可以查看执行计划阿！

SQL> explain plan for select * from stats_week where name =:gzw1;

Explained.

Elapsed: 00:00:00.01
SQL> @?/rdbms/admin/utlxpls

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------

--------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost |
--------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | |
|* 1 | TABLE ACCESS FULL | STATS_WEEK | | | |
--------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

1 - filter("STATS_WEEK"."NAME"=:Z)

Elapsed: 00:00:00.03
SQL> select * from stats_week where name=:gzw1;
SP2-0552: Bind variable "GZW1" not declared.
Elapsed: 00:00:00.00