Oracle database SQL statement execution plan, statement tracking and optimization instance

How to find the ones that consume the most system resources SQL Sentence? utilize I/O Optimize the identification of resource consuming methods, i.e AWR The report , Can make it easy .

When you identify the one most likely to go wrong SQL After the statement , The next step is how to track the execution of this statement , The most common way is to find out what SQL Statement execution plan .

With the increase of data in the database , The response speed of the system has become one of the main problems that the system needs to solve , A very important aspect of system optimization is SQL Statement optimization .

A large number of data point to inferior SQL Statement and quality SQL The speed difference between statements can be hundreds of times , For a system, it is not easy to realize the function , It's about writing high quality SQL Statement to improve the availability of the system .

01、 utilize autotrace track SQL sentence

utilize autotrace track SQL The code of the statement is as follows :

SQL> set autotrace on
SQL> select * from dual;

D
-
X

 Implementation plan 
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Plan hash value: 272002086

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| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT |    |     1 | 2 |     2   (0)| 00:00:01 |
| 1 | TABLE ACCESS