【文件属性】:
文件名称:在查询时尽量少用格式转换-ORACLE+SQL性能优化(全)
文件大小:2.32MB
文件格式:PPT
更新时间:2021-04-25 22:11:54
SQL
在查询时尽量少用格式转换
如用 WHERE a.order_no = b.order_no
不用
WHERE TO_NUMBER (substr(a.order_no, instr(b.order_no, '.') - 1)
= TO_NUMBER (substr(a.order_no, instr(b.order_no, '.') - 1)