Shulou(Shulou.com)06/01 Report--

The execution order of the query statement:

Select ename as name from scott.emp emp where emp.job=' CLERK' order by name

Select deptno,avg (sal), count () from scott.emp group by deptno order by count () desc

Select job,avg (sal) from scott.emp group by job having avg (sal) > 2000

1. First execute from to determine where the data comes from, and then execute the where condition to determine the qualified data. You can use the alias emp3 of table scoot.emp, and then perform group by grouping (filtering travel and then grouping) 4. Having packet filtering (having must appear with group by, without group by, there can be no having. Where condition can not appear statistical function grouping function) 5, execute select query query data 6, and finally execute order by to sort the checked data, so you can use the alias name of field eame after order by.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.