SQL (Standard Query Language) Yong Choi School of Business CSU, Bakersfield

2 Study Objectives Understand the basic commands and functions of SQL Learn how to use SQL to query a database to extract useful information Practice SQL

3 Introduction to SQL Standard Query Language (SQL) is a computer language for the relational database model. SQL is a nonprocedural language (click here for the example). So, it is much easier to use.here –what is to be done without having to worry about how it's to be done. Procedural language (click here for the example)here –Must be programmed correctly and compiled –Java, C++, and Pascal. SQL is relatively easy to learn –SQL commands set has a basic vocabulary of less than 100 words. Go To Next Topic

4 SQL Example SELECT ID, L_Name, F_Name, Salary, Dept_No FROM Employee; ID L_Name F_Name Salary Dept_No Kim John Johnson Steve Jonson Paul Lee Jim Basinger Jon Stone Sharon rows selected. Back

5 JAVA Example public class JavaProgramming { public static void main ( String[] args ) { long payAmount; payAmount = 123; System.out.println("The variable contains: " + payAmount ); } Output: The Variable contains 123. Back

6 Basic SQL Commands Followings are the most frequently used commands –Use always SELECT FROM –Use when conditions must be specified WHERE HAVING ORDER BY GROUP BY

7 The SELECT and FROM Statement Need both commands almost always….. –The SELECT statement is used to select data from a table. –The FROM statement is used to select tables. Syntax: –SELECT column_name(s) –FROM table_name To select all columns (fields) from a table, use * symbol instead of column names: –SELECT * –FROM table_name

8 The WHERE Statement To conditionally select data from a table, a WHERE clause can be added to the SELECT statement. Syntax: –SELECT column –FROM table –WHERE column operator value See next slide for various operators

9 SQL Comparison Operators FOR WHERE clause AND logical operator OR logical operator NOT Warehouse =‘3’ LIKE: LIKE ‘a*’, LIKE ‘*s’, Like ‘*Oxford*’ BETWEEN AND 78000

10 Semicolon after SQL Statements? Semicolon is the standard way to a block of SQL statement in database systems. So, you must use a semicolon at the end of a block of SQL statement. –Access SQL commands are not case sensitive but try to follow exact names for better readability. Download SQL data file form the class web site. –SQL_300.mdb

11 CustomerNumCustomerNameStreetCityStateZipBalanceCreditLimitRepNum 148Al's Appliance and Sport 2837 Greenway FillmoreFL33336$6,550$7,50020 OrderNumPartNumNumOrderedQuotedPrice 21608AT9411$21.95 OrderNumOrderDateCustomerNum /20/ Customer OrderLine Orders PartNumDescriptionOnHandClassWarehousePrice AT94Iron50HW3$24.95 Part Rep RepNumLastNameFirstNameStreetCityStateZipCommissionRate 20KaiserValerie624 RandallGroveFL33321$20,

12 SQL Preparation Review tables and relationships first… –Review each table in both views Design view Datasheet view –Recognize PK and FK information –Examine Relationships information SQL using Access –Design view of query  Select SQL View using Style button –No need to add tables (unlike QBE)

13 SQL Sample I’d like to know the list of CustomerNum and CustomerName. –SELECT CustomerNum, CustomerName –FROM Customer; I’d like to know the list of PartNum, Description, RepNum, and LastName –SELECT PartNum, Description, RepNum, LastName –FROM Part, Rep;

14 SQL Example 1 & 2 Example 1: –I’d like to know a list of the Customer number, Customer name, and balance of all customers. –Save as SQL 1 Example 2: –I’d like to know a list of the Order number, Part number, Price and Order Date. –Save as SQL 2

15 SQL Example 3 Restriction requirements –Where command –Exact Match Example 3: –I’d like to know customer names who are located in the city of Grove –Save as SQL 3

16 SQL Query to Find All Customers in ‘Grove’

17 SQL Example 4 Restriction requirements –Where command –Comparison operator Example 4: –I’d like to know a list of the number, name, credit limit, and balance for customers with credit limits that exceed their balances. –Save as SQL 4

18 Query to find Customers with Credit Limit Exceeding Balance

19 SQL Example 5 Restriction requirements –Where command –Compound conditions Example 5: –List the description of all parts that are located in warehouse 3 and for which there are more than 20 units on hand. –Save as SQL 5

20 SQL Query with Compound Condition using ‘AND’

21 SQL Example 6 Default value of ORDER BY: ascending Example 6: –List the number, name, and credit limit of all customers. Sort the customers by name in ascending order. –Save as SQL 6

22 SQL Query to Sort Data