Database written test-------------Identify employees ' names, salary, department name and department average salary exceeding department's average salary.

Source: Internet
Author: User

There is a period of time did not do the database problem, the interview by chance to do so a topic, feel good, with memory will be written down, and then implemented in the database once.

The topic is like this: an Employee table employee, including field id,name,salary,dep_no; A Departmental Information table department, which contains field Id,dep_no,name, where employee dep_no is associated department dep_no; Write SQL find out the names, salaries, department names and departments of employees who have exceeded the department's average salary. Average salary.

Here are the two tables I created:

DROP TABLE IF EXISTSDepartment;CREATE TABLEDepartment (IDint  not NULLAuto_incrementPRIMARY KEY, Dep_noint  not NULL, ' name 'VARCHAR( -) not NULL);INSERT  intoDepartment (Dep_no,name)VALUES(Ten,'Research Department');INSERT  intoDepartment (Dep_no,name)VALUES( -,'Testing Department');INSERT  intoDepartment (Dep_no,name)VALUES( -,'Finance Department');

DROP TABLE IF EXISTSemployee;CREATE TABLEemployee (' ID 'int  not NULLauto_increment, ' name 'varchar( -) not NULL, ' salary 'Double(Ten,2) not NULL DEFAULT 0, ' Dep_no 'INTEGER  not NULL,PRIMARY KEY(' id '));INSERT  intoEmployee (NAME,SALARY,DEP_NO)SELECT 'Bruce',15000.00, Dep_no fromDepartmentWHERE' Name '= 'Research Department';INSERT  intoEmployee (NAME,SALARY,DEP_NO)SELECT 'Kevin',16000.00, Dep_no fromDepartmentWHERE' Name '= 'Research Department';INSERT  intoEmployee (NAME,SALARY,DEP_NO)SELECT 'LWW',12000.00, Dep_no fromDepartmentWHERE' Name '= 'Finance Department';INSERT  intoEmployee (NAME,SALARY,DEP_NO)SELECT 'Linda',10000.00, Dep_no fromDepartmentWHERE' Name '= 'Finance Department';INSERT  intoEmployee (NAME,SALARY,DEP_NO)SELECT 'David',10000.00, Dep_no fromDepartmentWHEREName= 'Testing Department';INSERT  intoEmployee (NAME,SALARY,DEP_NO)SELECT 'Sandy',8000.00, Dep_no fromDepartmentWHEREName= 'Testing Department';INSERT  intoEmployee (NAME,DEP_NO)SELECT 'Dennis', Dep_no fromDepartmentWHEREName= 'Testing Department';

The analysis of the topic: first of all to get the name of the target staff, pay needless to be obtained from the employee table; As for the latter two data department name and department average salary, direct check department certainly not get, need two table joint query, may write this piece of sql:

SELECT AVG  as avg_sal,d.dep_no,d. ' Name '  from  WHERE=  e.dep_noGROUP by d.dep_no,d. ' Name ';

The reason why Dep_no,name two fields as a group field is because there is name in the following query target, and Dep_no as a unique identifier of the department, it is a natural grouping field, taking into account that the query results in this section are linked to the employee table, and the two can only be Dep_no connection.

Put the above results as temporary table tmp into the main query, and finally get:

SELECTE. ' Name ', e.salary,tmp.dep_name,tmp.avg_sal fromemployee E, (SELECT AVG(e.salary) asAvg_sal,d.dep_no,d. ' Name ' asDep_name fromEmployee E,department DWHERED.dep_no=E.dep_noGROUP  byd.dep_no,d. ' name ') TMPWHEREE.dep_no=Tmp.dep_no andE.salary>Tmp.avg_sal;

Search a circle, as if other places also have similar problems, but I think I do this version is very detailed, very valuable reference.

  

Database written test-------------Identify employees ' names, salary, department name and department average salary exceeding department's average salary.

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.