1. ITS232 Introduction To Database Management Systems
CHAPTER 7
An Introduction To SQL
Lab 2: Retriving Data From Multiple Tables
Siti Nurbaya Ismail
Faculty of Computer Science & Mathematics,
Universiti Teknologi MARA (UiTM), Kedah
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2. DML: Queries: SELECT Statement
The SELECT statement allows you to find, retrieve, and display data.
To execute the SELECT statement on a table, you must be the table owner, have DBA or SYSADM security privileges, or have the SELECT privilege for that table.
The result of SELECT statement is a set of rows known as the result set, which meets the conditions specified in the SELECT statement
SQL SELECT Syntax
Note
SQL is not case sensitive { SELECT is the same as select }
SELECT column_name(s)
FROM table_name;
SELECT *
FROM table_name;

3. DML: Queries: SQL Alias
You can give a table or a column another name by using an alias. This can be a good thing to do if you have very long or complex table names or column names.
An alias name could be anything, but usually it is short.
Usually it is used in multiple table joint.
SQL Alias Syntax For Tables
SQL Alias Syntax For Columns
SELECT column_name(s)
FROM table_name AS alias_name
SELECT column_name AS alias_name
FROM table_name

4. DML: Queries: SELECT Statement
staff
department
staffNO
name
city
salary
departNO
ABC987
Nadz
Kuala Lumpur
2300
0001
ABC988
Aina
Jerantut
2500
0002
ABC989
Halimaton
2200
ABC990
Norain
Johor
2000
0003
departNO
name
0001 IT
0002
Network
0003
Management
How do you list staff name and which deparment they work with?
The following statement list all the staff name.
The following statement list all the department name.
SELECT name
FROM staff;
SELECT name
FROM department;

5. DML: Queries: SELECT Statement
In order to list staff name with the coresponding deparment name they work with, the data must be retrive from 2 table which is, table staff and department.
In order to do so, both the table must be join, using either:
join predicate
JOIN keyword

6. DML: Queries: SELECT Statement with join predicate
staff
department
staffNO
name
city
salary
departNO
ABC987
Nadz
Kuala Lumpur
2300
0001
ABC988
Aina
Jerantut
2500
0002
ABC989
Halimaton
2200
ABC990
Norain
Johor
2000
0003
departNO
name
0001 IT
0002
Network
0003
Management
The following statement list all the name with the coresponding deparment name they work with.
name
Nadz IT
Aina
Network
Halimaton
Norain
Management
SELECT s.name, d.name
FROM staff AS s, department AS d
WHERE d.departNO = s.departNO;
join predicate

7. DML: Queries: SELECT Statement with JOIN keyword
staff
department
staffNO
name
city
salary
departNO
ABC987
Nadz
Kuala Lumpur
2300
0001
ABC988
Aina
Jerantut
2500
0002
ABC989
Halimaton
2200
ABC990
Norain
Johor
2000
0003
departNO
name
0001 IT
0002
Network
0003
Management
The following statement list all the name with the coresponding deparment name they work with.
name
Nadz IT
Aina
Network
Halimaton
Norain
Management
SELECT s.name, d.name
FROM staff AS s
JOIN department AS d
ON d.departNO = s.departNO;
JOIN keyword

8. SQL JOINs
The JOIN keyword is used in an SQL statement to query data from two or more tables, based on a relationship between certain columns in these tables.
Tables in a database are often related to each other with keys.
A primary key is a column (or a combination of columns) with a unique value for each row. Each primary key value must be unique within the table. The purpose is to bind data together, across tables, without repeating all of the data in every table.

9. SQL JOINs Different SQL JOINs JOIN / INNER JOIN
Return rows when there is at least one match in both tables
LEFT JOIN
Return all rows from the left table, even if there are no matches in the right table
RIGHT JOIN
Return all rows from the right table, even if there are no matches in the left table
FULL JOIN
Return rows when there is a match in one of the tables

10. SQL INNER JOIN SQL INNER JOIN Syntax SELECT column_name(s)
NOTE
INNER JOIN is the same as JOIN.
SELECT column_name(s)
FROM table_name1
INNER JOIN table_name2
ON table_name1.column_name = table_name2.column_name

11. DML: Two-Table Joins SELECT s.staffNAME
Besides INNER JOIN, you can also use the following statements to combines two tables with join conditions.
staff(staffNO, staffNAME, city, salary, departmentNO*)
department(departNO, departNAME)
SELECT s.staffNAME
FROM staff AS s, department AS d
WHERE (d.departNO=s.departNO) AND d.departNAME=“IT”;
SELECT staff.staffNAME,department.departNAME
FROM staff
INNER JOIN department
ON department.departNO=staff.departNO;

12. DML: Multiple-Table Joins
A multiple table join is a join of more than two tables with join conditions for pairs of table.
A join condition is a comparison (relational operators) on two columns from each table.
Following is a three table joins which selects all the customer name that order biscuit Tart Nenas Gunting.
customer(custNO, custNAME, cust )
biscuit(bisNO, bisNAME, bisFLAVOUR, bisPRICE)
order(orderNO,*custNO,*bisNO, orderadate, qty, status)
SELECT custNAME
FROM customer AS c, biscuit AS b, order AS o
WHERE c.custNO=o.custNO AND o.bisNO=b.bisNO
AND b.bisNAME=“Tart Nenas Gunting“;

13. DML: Multiple-Table Joins
List down all customer name, biscuit name and order quantity that customer had order with confirm status.
tblcustomer(custNO, custNAME, cust )
tblbiscuit(bisNO, bisNAME, bisFLAVOUR, bisPRICE)
tblorder(orderNO,*custNO,*bisNO, orderadate, qty, status)