CPSC 421: Database Management Systems

Transcription

1 CPSC 421: Database Management Systems MySQL Basics Getting Started The server The MySQL Shell Creating Tables Loading data Querying Data Prepared Statements & Views Getting Started MySQL Website Download The community server version (free) I installed version 5.1 (other version avail.) Almost all platforms supported (OS X, Windows, Linux, ) Binary installers available Should read installation instructions (if installing on your own) Documentation Should read about setting up accounts, passwords, etc. in manual Also, section on database administration is useful 2 1

2 For this course Matt Bergman has set up MySQL on ada, windows/linux servers You can use one of these, install your own version on a personal machine, or use an entirely different DBMS If you use the installation at Gonzaga please send to Matt to request an account If you are going to use a different DBMS let me know which you are planning on using other options might be PostgreSQL, MonetDB/SQL (also free) or Oracle, DB2, SQL Server, MS Access* (commercial) 3 About MySQL Features Open-source (GPL) A Real DBMS (e.g., disk storage depending on storage engine) Supports much of SQL (99) but not all Many advanced features, e.g., stored procedures, triggers, views, Different storage engines, per table This can be a bit confusing because of different choices MySQL allows new engines to be created ( Pluggable API ) Caching Replication Transactions (InnoDB, others) 4 2

3 Starting and Stopping the Server Typical installation Start the server (see installation instructions) Run mysql command (e.g., /usr/local/mysql/bin/mysql) Create accounts, set up passwords and priviledges Alternatively, you can use the MySQL GUI Tools This is a lot easier! MySQL Administrator for doing above and more MySQL Query Browser for creating tables, writing and running queries, etc. 5 MySQL Monitor (client app) Command line application mysql $ mysql $ mysql -u user -p $ mysql -h host -u user -p From the monitor, you can: Perform admin, exec. queries, check system status, etc. For example: [sbowers:~]$ mysql -u sbowers -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 22 Server version: MySQL Community Server (GPL) Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> SHOW DATABASES; Database information_schema row in set (0.00 sec) mysql> quit Bye [sbowers:~]$ 6 3

4 Creating a Database As root (depending on permissions) mysql> CREATE DATABASE <dbname>; Creates a database, and now you can add tables, etc. To select the database: mysql> USE <dbname>; Can start the monitor in the database: $ mysql -u user -p <dbname> Can see the tables of the db: mysql> show tables; Can also do this via MySQL Query Browser 7 Creating Tables Can issue SQL statements via the monitor, including create table mysql> USE mydb mysql> CREATE TABLE ingredients (id INT, name VARCHAR(30)); Creates a 2-column table To verify that your table was created: mysql> DESCRIBE ingredients; Field Type Null Key Default Extra id int(11) YES NULL name varchar(30) YES NULL rows in set (0.08 sec) To remove the table: Mysql> DROP TABLE ingredients; 8 4

5 Creating Tables The MySQL Query Browser can also be used to create tables 9 Creating Tables MySQL Query Browser exposes more options, e.g., allowing the storage engine of a table, and much more InnoDB is (currently) most feature rich (transactions, indices, etc.) MyISAM is the other major engine Generates underlying SQL, which is sent to the server: CREATE TABLE `mydb`.`ingredients` ( `id` INT, `name` VARCHAR(30) ) ENGINE = InnoDB CHARACTER SET utf8; 10 5

6 Loading Data Again, can issue insert command: mysql> INSERT INTO ingredients VALUES (1, jalapeno ); mysql> INSERT INTO ingredients VALUES (2, habanero ); Can also use the load data command: mysql> LOAD DATA LOCAL INFILE ~/ingredients.txt INTO TABLE ingredients; The data file should be tab-delimitted with each record on a newline. Nulls values are denoted by \N, e.g.: 1 jalapeno 2 habanero 3 tomatillo 4 \N Data can be removed using delete command: mysql> DELTE FROM ingredients WHERE id < 10; 11 Querying Data Can issue queries directly in monitor: mysql> SELECT * FROM ingredients; id name 1 'jalapeno' 2 'habanero' 3 'tomatillo' 4 'bell pepper' 5 'onion' 6 'cayenne' 7 NULL As well as from the MySQL Query Browser 12 6

7 Explaining Queries Can prepend queries with Explain to show information the query optimizer uses: mysql> EXPLAIN SELECT * FROM ingredients WHERE id=3 or id=4; id select_type table type possible_keys key key_len ref rows Extra SIMPLE ingredients ALL NULL NULL NULL NULL 7 Using where Can run Explain through MySQL Query Browser as well The result is more interesting as queries become more complicated 13 Prepared Statements Allow you to assign a name to an SQL query, which typically contains parameters Stored on the server and executed by passing parameter values Here is a simple example: mysql> PREPARE get_ingredient_name FROM 'select name from ingredients where id=?'; mysql> = 3; mysql> EXECUTE get_ingredient_name name 'tomatillo' row in set (0.00 sec) mysql> DEALLOCATE PREPARE get_ingredient_name Often used when building applications that interact with a database (through a prepared statement API) 14 7

8 Views Views provide a way to name a query, and then use that name as a relation in another query Here is a simple example: mysql> CREATE VIEW peppers AS SELECT * FROM ingredients WHERE id IN(1,2,4,6); mysql> SELECT * FROM peppers; id name 1 'jalapeno' 2 'habanero' 4 'bell pepper' 6 'cayenne' 15 MySQL in batch mode Instead of using mysql interactively, you can also use it to run scripts (series of mysql commands) For example: $ mysql < batch-file $ mysql -u user -p < batch-file etc. You can also load your script via mysql: mysql> source batchfile Why use batch files? Saves typing Stores your database table def s, views, etc., in case you need to start over Easy to edit/extend your scripts (e.g., if trying to figure out the right query) Can create your database on different servers, etc. Documentation of what you did Etc. 16 8

9 Lots more MySQL has many features we did not discuss the MySQL documentation is a great resource some things you might want to look at are: Transactions Stored Procedures How to access MySQL via JDBC Crash recovery Storage engines How to backup your database Limitations of SQL support, and workarounds (e.g., minus) Spatial Extensions Functions and operators Data types PHP support other tools supporting MySQL, e.g., phpmyadmin (web-based database administration) 17 9