Introduction to SQL Yong Choi School of Business CSU, Bakersfield
Study Objectives • Understand the basic commands and functions of SQL • Learn how SQL is used for data manipulation (to add, modify, delete, and retrieve data) • Learn how to use SQL to query a database to extract useful information • Learn how SQL is used for data administration (to create tables, indexes, and views) • Practice SQL
Ideal Database Language Requirements • Create database and table structures. • SQL has a data definition component that gives us the ability to meet this requirement. • Manage the data component of the database. • SQL gives us a set of commands to add, update, and delete data within the database tables. • Provide detailed data query capability. • "Standard" SQL uses a set of approximately thirty commands that allow us to retrieve data and to convert the raw data into useful information.
Introduction to SQL • Standard Query Language (SQL) is the relational model’s standard language. • The original version of SQL was developed at IBM's San Jose Research Laboratory. This language, originally called Sequel. The Sequel language has evolved since then, and its name has changed to SQL (Structured Query Language). • In 1986, the American National Standards Institute (ANSI) published an SQL standard. • In 1992, work was completed on a significantly revised version of the SQL standard (SQL-92).
Introduction to SQL (con’t) • SQL is relatively easy to learn • SQL commands set has a basic vocabulary of less than 100 words. • SQL is a nonprocedural language. So, it is much easier to use. • Its user merely commands what is to be done without having to worry about how it's to be done. • Procedural language: COBOL, C, or Pascal.
Basic Structure of SQL Queries • SELECT <attribute list> • FROM <table list> • WHERE <condition> • GROUP BY < grouping attribute(s)> • HAVING <group condition> • ORDER BY <attribute list>
The SELECT and FROM Statement • The SELECT statement is used to select data from a table. The tabular result is stored in a result table (called the result set). The FROM statement is used to select tables. • Syntax: • SELECT column_name(s) • FROM table_name • To select all columns from a table, use a * symbol instead of column names: • SELECT * FROM table_name
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
Typical Data Types • INTEGER: Numbers without a decimal point • SMALLINT: Uses less space than INTEGER • DECIMAL(p,q): P number of digits; q number of decimal places • CHAR(n): Character string n places long • DATE: Dates in DD-MON-YYYY or MM/DD/YYYY
Semicolon after SQL Statements? • Semicolon is the standard way to separate each SQL statement in database systems that allow more than one SQL statement to be executed in the same call to the server. • MS Access and SQL Server do not require to put a semicolon after each SQL statement, but other database SQLs force you to use it such as Oracle. So, you must use a semicolon for this class. • Access SQL commands are not case sensitive (including table and attribute names) but try to follow exact names for better readability. • Download SQL data file form the class web site.
CustomerNum OrderNum OrderNum RepNum PartNum LastName Description OrderDate PartNum CustomerName FirstName NumOrdered OnHand CustomerNum Class Street QuotedPrice Street Warehouse City Price State City Zip State Commission Zip Balance Rate CreditLimit RepNum 148 21608 20 21608 AT94 Kaiser Iron 10/20/2003 AT94 Al's Appliance and Sport Valerie 11 50 148 HW 624 Randall $21.95 2837 Greenway 3 Grove $24.95 FL Fillmore 33321 FL $20,542.50 33336 $6,550 0.05 $7,500 20 Customer OrderLine Order Part Rep
Example 1 • Example 1: Save as example 1 • List the number, name, and balance of all customers.
Example 1 SELECT Customernum, CustomerName, Balance FROM Customer;
Example 2 • Example 2: Save as example 2 • List the complete Part table. • Use of “ * “
Example 2 SELECT * FROM Part;
SQL Example – WHERE clause • Example 3: Save as example 3 • List the name of every customers with $10,000 credit limit. • Credit limit must be equal to $10000
Example 3 SQL Query with Where Condition
Example 3 SELECT Customername FROM Customer WHERE
SQL Example – WHERE clause • Example 4: Save as example 4 • Find the name of customer 148.
Example 4 SQL Query to Find Customer 148
Example 4 SELECT CustomerNum FROM Customer WHERE
SQL Comparison Operators For WHERE clause NOT Warehouse =‘3’ LIKE: LIKE ‘a*’, LIKE ‘*s’, Like ‘*Oxford*’ (NOT) BETWEEN 45000 AND 78000 (NOT) IN (123, 345)
SQL Examples • Example 5: Save as example 5 • Find the customer name for every customer located in the city of Grove
Example 5 SELECT Customername FROM Customer WHERE
SQL Examples • Example 6: Save as example 6 • List the number, name, credit limit, and balance for customers with credit limits that exceed their balances.
Example 6 SELECT CustomerName, CustomerName, CreditLimit, Balance FROM Customer WHERE
SQL Examples – Compound Conditions • Example 7: Save as example 7 • List the description of all parts that are located in warehouse 3 and for which there are more than 20 units on hand.
Example 7 SQL Query with Compound Condition using ‘AND’
Example 7 SELECT Description FROM Part WHERE
SQL Examples – Compound Conditions • Example 8: Save as example 8 • List the descriptions of all parts that are located in warehouse 3 or for which there are more than 20 units on hand.
Example 8 SQL Query using ‘OR’
Example 8 SELECT Description FROM Part WHERE
SQL Examples • Example 9: Save as example 9 • List the description of all parts that are not in warehouse 3. • Use “NOT” (i.e., where NOT A = 100;)
Example 9 SQL Query using ‘NOT’
Example 9 SELECT Description FROM Part WHERE NOT
SQL Examples • Example 10: Save as example 10 • List the number, name, and balance of all customers with balances greater than or equal to $1,000 and less than or equal to $5,000. • (NOT) BETWEEN 45000 AND 78000
Example 10 Query with ‘BETWEEN’ Operator
Example 10 SELECT CustomerNum, CustomerName, Balance FROM Customer WHERE
SQL Examples – Computed Field • Computed field can involve: • addition(+), subtraction(-), Multiplication(*), or division (/) • Example 11: Save as example 11 • List the number, name and available credit for all customers. • Use “AS” for assigning a new field name
Example 11 SQL Query with Computed Field
SQL Examples – Computed Field • Computed field can involve: • addition(+), subtraction(-), Multiplication(*), or division (/) • Example 12: Save as example 12 • List the number, name, and available credit for all customers with credit limits that exceed their balances.
Example 12 SQL Query with Computed Field and Condition
SQL Examples – LIKE and IN • Example 13: Save as example 13 • List the number, name, and complete address of every customer located on a street that contain the letters “Oxford.” • Customer names begin with B: Like B* • Customer names end with E: Like *E • Fine exact customer last name: like ‘*Choi*’
Example 13 SQL Query with ‘LIKE’ Operator
SQL Examples – LIKE and IN • Example 14: Save as example 14 • List the number, name, and credit limit for every customer with a credit of $7,500, $10,000, or $15,000. • IN (7500, 10000, 15000);
Example 14 SQL Query with ‘IN’ Operator