Sams Teach Yourself SQL in 24 Hours, Third Edition By Ronald R. Plew, Ryan K. Stephens
Table of Contents
Hour 13. Joining Tables in Queries
The following workshop is composed of a series of quiz questions and practical exercises. The quiz questions are designed to test your overall understanding of the current material. The practical exercises are intended to afford you the opportunity to apply the concepts discussed during the current hour, as well as build upon the knowledge acquired in previous hours of study. Please take time to complete the quiz questions and exercises before continuing. Refer to Appendix C,"Answers to Quizzes and Exercises," for answers.
Quiz
1:
What type of join would you use to return records from one table, regardless of the existence of associated records in the related table?
2:
The join conditions are located in what part of the SQL statement?
3:
What type of join do you use to evaluate equality among rows of related tables?
4:
What happens if you select from two different tables but fail to join the tables?
5:
Use the following tables:
ORDERS_TBL
ORD_NUM
VARCHAR(10)
NOT NULL
PRIMARY KEY
CUST_ID
VARCHAR(10)
NOT NULL
PROD_ID
VARCHAR(10)
NOT NULL
QTY
Integer(6) NOT NULL
ORD_DATE
DATETIME
PRODUCTS_TBL
PROD_ID
VARCHAR(10)
NOT NULL
PRIMARY KEY
PROD_DESC
VARCHAR(40)
NOT NULL
COST
DECIMAL(,2) NOT NULL
6:
Is the following syntax correct for using an OUTER JOIN?
SELECT C.CUST_ID, C.CUST_NAME, O.ORD_NUM FROM CUSTOMER_TBL C, ORDERS_TBL O WHERE C.CUST_ID(+) = O.CUST_ID(+)
Exercises
1:
Invoke MySQL, point to your learnsql database, and type the following code and study the result set (Cartesian product):
SELECT E.LAST_NAME, E.FIRST_NAME, EP.DATE_HIRE FROM EMPLOYEE_TBL E, EMPLOYEE_PAY_TBL EP;
2:
Type the following code to properly join the EMPLOYEE_TBL and EMPLOYEE_PAY_TBL tables:
SELECT E.LAST_NAME, E.FIRST_NAME, EP.DATE_HIRE FROM EMPLOYEE_TBL E, EMPLOYEE_PAY_TBL EP WHERE E.EMP_ID = EP.EMP_ID;
3:
Write a SQL statement to return the EMP_ID, LAST_NAME, and FIRST_NAME from the EMPLOYEE_TBL and SALARY and BONUS from the EMPLOYEE_PAY_TBL.
4:
What is the average employee salary per city?
5:
Try writing a few queries with join operations on your own.