SQL has several parts: Major ones: DDL – Data Definition Language {Defining, Deleting, Modifying relation schemas} DML – Data Manipulation Language {Inserting, Deleting, Modifying tuples in database} Embedded SQL – defines how SQL statements can be used with general-purposed programming

SQL For help: shell> mysql --help Using SQL: On any solaris/linux you have to use this to log on to MySQL: shell> /usr/local/mysql/bin/mysql -h faure -D loginname -p Basic Query: select A 1, A 2,…,A n from r 1, r 2, …,r m where P A 1, A 2,…,A n represent attributes r 1, r 2, …r m represent relations P represents predicate (guard condition)

Representations: Prompt Meaning mysql> Ready for new command. -> Waiting for next line of multiple-line command. ‘> Waiting for next line, collecting a string that begins with a single quote (` ’ ’). “> Waiting for next line, collecting a string that begins with a double quote (` ” ’). mysql> SELECT * -> FROM my_table -> WHERE name = “Smith” AND age < 30; mysql> SELECT * FROM my_table WHERE name = “Smith” AND age < 30; \c to cancel the execution of a command Keywords may be entered in any letter case: mysql> SELECT VERSION(), CURRENT_DATE; mysql> select version(), current_date; mysql> SeLeCt vErSiOn(), current_DATE; mysql> SELECT SIN(PI()/4), (4+1)*5;

Creating and Using a Database mysql> SHOW DATABASES; SHOW statement can be used to find out the databases currently existing on the server mysql> USE testdb testdb is a database name. USE command does not need a semi colon and must be given in a single line. Database needs to be invoked in order to use it. mysql> CREATE DATABASE example; Database names are case-sensitive unlike keywords; Same applies for table names So example != Example != EXAMPLE or some other variant

Creating a Table mysql> SHOW TABLES; Displays the current list of tables mysql> CREATE TABLE pet (name VARCHAR(20), owner VARCHAR(20), -> species VARCHAR(20), sex CHAR(1), birth DATE, death DATE); mysql> SHOW TABLES; Will display the table with the table name pet Verification of the table can be done with DESCRIBE command mysql> DESCRIBE pet; | Field | Type | Null | Key | Default | Extra | | name | varchar(20) | YES | | NULL | | | owner | varchar(20) | YES | | NULL | | | species| varchar(20) | YES || NULL | | | sex | char(1) | YES | | NULL | | | birth | date | YES| | NULL | | | death | date | YES || NULL | |

Loading Data into a Table LOAD DATA uses a text file with single record in a line that match the attributes in the table. Useful for inserting when multiple records are involved. Example: pet.txt is a text file with a single record Nameowner species sex birth death WhistlerGwen bird \N \N mysql> LOAD DATA LOCAL INFILE "pet.txt" INTO TABLE pet; INSERT command can be used when records needs to be inserted one at a time. NULL can be directly inserted in the field column Example: mysql> INSERT INTO pet -> VALUES ('Puffball','Diane','hamster','f',' ',NULL); Using User Variables select from shop; select * from shop where or

Examples of some common queries CREATE TABLE shop ( article INT(4) UNSIGNED ZEROFILL DEFAULT ‘0000' NOT NULL, dealerCHAR(20) DEFAULT ‘’NOT NULL, price DOUBLE(16,2) DEFAULT '0.00’ NOT NULL, PRIMARY KEY(article, dealer)); INSERT INTO shop VALUES (1,'A',3.45),(1,'B',3.99),(2,'A',10.99),(3,'B',1.45),(3,'C',1.69), (3,'D',1.25),(4,'D',19.95); mysql> SELECT * FROM shop; | article | dealer | price | | 0001 | A | 3.45 | | 0001 | B | 3.99 | | 0002 | A | | | 0003 | B | 1.45 | | 0003 | C | 1.69 | | 0003 | D | 1.25 | | 0004 | D | | The maximum value for a column The row holding the maximum of a certain column Maximum of column per group The rows holding the group-wise maximum of a certain field

SELECT MAX(article) AS article FROM shop SELECT article, dealer, price FROM shop WHERE price=(SELECT MAX(price) FROM shop) (or) 1.Get the maximum price value from the table with a SELECT statement. 2.Using this value compile the actual query: SELECT article, dealer, price FROM shop WHERE price=19.95 SELECT article, MAX(price) AS price FROM shop GROUP BY article SELECT article, dealer, price FROM shop s1 WHERE price=(SELECT MAX(s2.price) FROM shop s2 WHERE s1.article = s2.article);