PL / SQL query optimization of the five Principles and Examples

But basically these few, for example will be described later

Use of a query or high-level functions to reduce the sub
2, the appropriate use of the index
3, note associated conditions associated multi-table
4, the number of planned to take a good way of writing table, see table to be used;
5, should be avoided term use is not a very resource-consuming, if they can not try to do (with the key query is not like taboo)
6, sub-queries do not write in conditions where write in select years;

Example 1 (try not to use a key not like the query)

select *
       from IFSAPP.SHOP_ORD
 where DATE_ENTERED>=DATE'2019-11-1'
 AND DATE_ENTERED<= DATE '2019-11-30'
 AND CONTRACT='PPCD' 
 AND PART_NO NOT IN (SELECT PART_NO FROM IFSAPP.SHOP_ORD WHERE PART_NO LIKE'45%'OR PART_NO LIKE '50%')

The following three minutes 52 seconds

select *
       from IFSAPP.SHOP_ORD
 where DATE_ENTERED>=DATE'2019-11-1'
 AND DATE_ENTERED<= DATE '2019-11-30'
 AND CONTRACT='PPCD' 
 AND SUBSTR(PART_NO,1,2) NOT IN ( '50','45')

The following took 57seconds

select *
  from IFSAPP.SHOP_ORD so1
 where DATE_ENTERED >= DATE '2019-11-1'
   AND DATE_ENTERED <= DATE '2019-11-30'
   AND CONTRACT = 'PPCD'
   AND not exists
 (SELECT 1
          FROM IFSAPP.SHOP_ORD so2
         WHERE so1.contract = so2.contract
           and so1.order_no = so2.order_no
           and so1.part_no = so2.part_no
           and (PART_NO LIKE '45%' OR PART_NO LIKE '50%')) 

Why is efficiency so high? I think the next.
The following took 55seconds

select *
  from IFSAPP.SHOP_ORD
 where DATE_ENTERED >= DATE '2019-11-1'
   AND DATE_ENTERED <= DATE '2019-11-30'
   AND CONTRACT = 'PPCD'
   and instr(PART_NO, '45') != 1
   and instr(PART_NO, '50') != 1

Multi 56 seconds

SQL optimization article: https: //blog.csdn.net/jianzhang11/article/details/102867120

ORACLE operation and maintenance
https://bbs.csdn.net/topics/395382796