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 | A2-3039 | ext:2561 | sitinurbaya@kedah.uitm.edu.my | 012-7760562 |

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;

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

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;

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

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

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

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.

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

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

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;

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, custEMAIL) 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“;

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