Oracle和TOAD的sql语句解析阶段
调整大型 sql 字符串时是否只需要查看解释计划？ 因为当我在 TOAD for Oracle（生成解释计划）中按下 Ctrl+E 时，这需要几秒钟的时间。 TOAD 是否除了生成解释计划之外还做了其他任何事情，或者它真的让特定 sql 语句的解析阶段需要 2-3 秒吗？
当我查看解释计划时，我真的看不到如何优化sql字符串了。所以我想在执行计划之前可能会发生一些事情？
提前致谢 Martin（新手预言机调优专家）
Is it only the explain plan to look in when tuning a large sql string?
Because when I push Ctrl+E in TOAD for Oracle (which generates explain plan), this takes several seconds. Does TOAD do anything more than generating the explain plan, or is it really so that the parse phase takes 2-3 seconds for that specific sql statement?
I really can't see how to optimize the sql string anymore when looking at the explain plan. So I thought maybe there is something going on BEFORE executing the plan?
thanks in advance
Martin (newbie oracle tuning expert)
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解释计划不会告诉您一切 - Oracle 只是告诉您查询成本的估计。
要获得查询的真实成本，您必须实际执行它并随后检查性能（例如使用 tkprof）。
我建议查看 Asktom，例如
http://asktom.oracle。 com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:8764517459743
并获得一本关于 Oracle 性能调优的好书（例如 Tom Kyte 的《Effective Oracle by Design》）。
The explain plan doesn't tell you everything - Oracle just tells you an estimate of the costs of your query.
To get the real costs of your query, you have to actually execute it and check the performance afterwards (e.g. using tkprof).
I'd recommend checking out Asktom, e.g.
http://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:8764517459743
and getting a good book on Oracle performance tuning (e.g. "Effective Oracle by Design" by Tom Kyte).