1. Structured Query Language SQL: An Introduction

2. SQL (Pronounced S.Q.L) The standard user and application program interface to a relational database is the Structured Query Language (SQL) SQL statements are used both for interactive queries for information from a relational database and for gathering data for reports – SQL uses keywords to interact with databases – It allows creating a database, populating, and querying it – In this slide we learn to apply MySQL Workbench to do all of these You can also use MySQL client

3. Create a Database/Table The syntax to create a database : CREATE DATABASE databaseName //Comment: SQL is case sensitive! The CREATE keyword is also used to create a table CREATE TABLE tablename //Capitalize keywords for clarity! ( Column1 description, //define each column Column2 description, // put a comma after each … ) Note: text written after // is comment, and is NOT part of the syntax!

4. Use MySQL to name the database Connect to MySQL// Read Chapter 4 Ullman – Make sure you have permission to create database CREATE DATABASE sitename; // end each statement with a ; USE sitename; // tells MySQL that you want to use the database from here on

5. Create the users Table in the Database CREATE TABLE user ( User_id MEDIUMINT UNSIGNED NOT NULL AUTO_INCREMENT, first_name VARCHAR(20) NOT NULL, Last_name VARCHAR(40) NOT NULL, email VARCHAR(60) NOT NULL, pass CHAR(40) NOT NULL, registration_date DATETIME NOT NULL, PRIMARY KEY (user_id), ); NOTE: The user table was designed in Chapter 4 Ullman’s book!

6. Confirm that the table exists SHOW TABLES; SHOW CCOLUMNS FROM users;

7. Populating the table Now that the table exists, insert records into it For this purpose we use the INSERT syntax: When we want only to enter values for certain columns: INSERT INTO tablename (column1, column2, …) VALUES (value1, value2, …); // Columns not given a value will get NULL unless they have a default // value. If they are NOT NULL and have no default there will be an error When we want to enter values for all columns use the following: INSERT INTO tablename VALUES (value1, NULL, value2, value3, …)

8. Inserting multiple rows (records) INSERT INTO tablename (column1, column2) VALUES (valueA, valueB), (valueC, valueD), (valueE, valueF), // this is not supported by all database systems (only by MySQL)

9. Insert real data into the users table INSERT INTO users (first_name, last_name, email, pass, registration_date,) VALUES (‘Hassan’, ‘Babaie’, ‘mylonite_7@yahoo.com’, SHA1(‘mypassword’), NOW()); //or without naming columns INSERT INTO users VALUES (NULL, ‘Hassan’, ‘Babaie’, ‘mylonite_7@yahoo.com’, SHA1(‘mypassword’), NOW()); // note: NULL is for the user_id (since all values must be provided!) //Comments: // note: put strings in “quotation marks”! // char, varchar, and text are strings! // NULL should not be quoted // backslash escapes a mark, e.g., O’clock is written as ‘O\’clock’ //the SHA1() and NOW() are functions. //the SHA1() encripts data to a 40 character long string, hence //CHAR(40) is used for password

10. Joins Table joins are used 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 Table Store_Information store_nameSalesDate Los Angeles$1500Jan-05-1999 San Diego$250Jan-07-1999 Los Angeles$300Jan-08-1999 Boston$700Jan-08-1999

11. Table Geography Region_namestore_name EastBoston EastNew York WestLos Angeles WestSan Diego

12. To get the sales information by region, we have to combine the information from the two tables These two tables are linked by the common field, "store_name“ The following SQL will retrieve the sales data by the region. SELECT A1.region_name REGION, SUM(A2.Sales) SALES FROM Geography A1 JOIN Store_Information A2 ON A1.store_name = A2.store_name GROUP BY A1.region_name Result: REGIONSALES East$700 West$2050

13. Join 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

14. Views A Database View is a subset of the database sorted and displayed in a particular way For each view, you can control which columns are displayed, what order they are displayed in, how the data is sorted, and what types of records to display A view consists of rows and columns just like a table The difference between a view and a table is that views are definitions built on top of other tables (or views), and do not hold data themselves If a data item is changing in the underlying table, the same change is reflected in the view A view can be built on top of a single table or multiple tables. It can also be built on top of another view

15. View Customer Table CREATE TABLE Customer (First_Name varchar(100), Last_Name varchar(100), Address varchar(50), City varchar(30), Country varchar(25), Birth_Date date NOT NULL) Use the following syntax to create a view called V_Customer that contains only the First_Name, Last_Name, and Country columns from this table CREATE VIEW V_Customer AS SELECT First_Name, Last_Name, Country FROM Customer Now we have a view called V_Customer with the following structure: View V_Customer (First_Name char(100), Last_Name char(100), Country char(25))

16. Alter Table Alter Table - Once a table is created in the database, you can use the Alter statement to change the structure of the table For example: Add a column Drop a column Change a column name Change the data type for a column ALTER table Customer add Gender char(1) ALTER table Customer drop Country

17. Drop Table Drop Table - Sometimes we may need to delete a table in the database This allows to get rid of tables not needed anymore and frees up database space Use the following command to delete the Customer table. DROP TABLE Customer

18. Truncate Table TRUNCATE TABLE - Sometimes we may need to delete all of the data in a table One way of doing this is with DROP TABLE But what if we wish to simply get rid of the data but not the table itself? For this, we can use the TRUNCATE TABLE command Use the following command to delete all data in Customer table. TRUNCATE TABLE Customer

19. Insert Into INSERT INTO Statement – Insert statement is used to add one or more rows to a table INSERT INTO Customer values ('4','Adams','Joe') – adds one row INSERT INTO Store_Information (store_name, Sales, Date) SELECT store_name, Sales, Date FROM Sales_Information WHERE Year(Date) = 1998

20. Update UPDATE Statement - allows to update data in an existing table UPDATE Store_Information SET Sales = 2000 WHERE store_name = "Los Angeles" AND Date = "Jan-08-1999"

21. Delete DELETE Statement – allows to remove rows from a table DELETE FROM Store_Information WHERE store_name = "Los Angeles"

22. Stored procedures A stored procedure is executable code that is associated with, and generally stored in, the database Stored procedures usually collect and customize common operations, like inserting a row into a table, gathering statistical information about usage patterns, or encapsulating complex business logic and calculations