Database - mysql
description
Transcript of Database - mysql
Database - mysql
Contents
Database – DBMS– Relational model
SQL– MySQL
Database
Database– a collection of data– Entity, relationship
DBMS– Database management system
DBMS
Why use a DBMS?– efficient access – reduced application development
time– data integrity and security– concurrent access– recovery from system crash
Relational model
Most widely used data model Relation
– A set of records– Schema
• Name of a relation, name of each fields
– Instance• A table with rows and columns
Students(sid:string, sname:string, snum:integer)
sid sname snum
euny Chang Eun Young 99
cavalist Ryu Han Seung 99
netj Jaeho Shin 00
Fields (attributes, columns)
Tuples (records, rows)
Field names
SQL
Structured query languageStandard language for interacting
with a DBMSData definitionManipulation
MySQL
Connect– mysql [–h host] [–u user] [–p[password]] [dbname]
>mysql -u root -p test
Enter password: ********
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 14 to server version: 3.23.34a
Type 'help;' or '\h' for help. Type '\c' to clear the buffer
mysql>
MySQL
Data definition
– CREATE/DROP DATABASE dbname;– SHOW DATABASES;– USE dbname;
– CREATE TABLE table_name (field_name type,.., constraints,..);
– SHOW TABLES;– SHOW COLUMNS FROM table_name;– DROP TABLE table_name;
MySQL
Data manipulation
– INSERT INTO table_name [(field_name,..)]
VALUES (value,..);
– DELETE FROM table_name WHERE condition;
– UPDATE table_name SET field_name=value,.. [WHERE condition];
MySQL
Data manipulation(2)
– SELECT field_name [as field_name],.. FROM table_name [WHERE condition] [ORDER BY field_name];
– =, <, >, AND, OR, NOT (field_name LIKE “_%….”)
MySQL
ALTER TABLE
– ALTER TABLE table_name [RENAME new_table_name]/ [ADD field_name type]/ [DROP field_name]/ [CHANGE name new_name new_type];
mysql> show databases;
+----------+
| Database |
+----------+
| mysql |
| test |
+----------+
2 rows in set (0.00 sec)
mysql> use test;
Database changed
mysql> create database test2;
Query OK, 1 row affected (0.00 sec)
mysql> CREATE TABLE Students(
-> sid VARCHAR(8) NOT NULL,
-> sname VARCHAR(20),
-> snum INT,
-> PRIMARY KEY(sid));
Query OK, 0 rows affected (0.01 sec)
MySQL Data Types
Type Size Description
inttinyint,smallint,mediumint,bigint
4 bytes1,2,3 and 8 bytes
2^32 values
floatdouble
4 bytes8 bytes
Date 3 bytes In the format of YYYY-MM-DD
Time 3 bytes In the format of HH:MM:SS
char[length]varchar[length]
fiString length + 1 byte
Fixed length stringVariable length from 0 to 255 characters long
mysql> show tables;+----------------+| Tables_in_test |+----------------+| students |+----------------+1 row in set (0.00 sec)
mysql> show columns from students;+-------+-------------+------+-----+---------+-------+| Field | Type | Null | Key | Default | Extra |+-------+-------------+------+-----+---------+-------+| sid | varchar(8) | | PRI | | || sname | varchar(20) | YES | | NULL | || snum | int(11) | YES | | NULL | |+-------+-------------+------+-----+---------+-------+3 rows in set (0.01 sec)
Primary KeyPrimary Key is a column or set of columns Uniquely identifies the rest of the data in
any given row.
For Example: in the employee table, employee number is the primary key.
Foreign Key
A foreign key is a column in a table
This column is a primary key of another table
Any data in a foreign key column must have corresponding data in the other table
Foreign Key
The goal of using foreign keys is that tables can be related without repeating data
Note that foreign keys in SQL are used to check and enforce referential integrity, not to join tables. If you want to get results from multiple tables from a SELECT statement, you do this by performing a join between them:SELECT * FROM t1, t2 WHERE t1.id = t2.id;
employer
Create table with foreign keys
create table employee2 (empno smallint(4) not null, salary float,primary key (empno)) type = innodb;
create table employer (id smallint(4), employee_no smallint(4), index employ_ind (employee_no), foreign key(employee_no) references employee2(empno) on delete cascade) type=innodb;
empno (PK)
salary
100 200.85
200 129.54
300 98.17
id employee_no(FK)
51 100
52 100
53 200
54 300
employee2
MySQL Table Types
If we want to use Foreign Key– InnoDB tables
Otherwise– Default table type, MyISAM
In SQL queries you can freely mix InnoDB type tables with other table types of MySQL, even within the same query.
mysql> INSERT INTO Students -> VALUES ('euny', 'Chang Eun-young', 99);Query OK, 1 row affected (0.00 sec)…
mysql> SELECT * FROM Students;+----------+-----------------+------+| sid | sname | snum |+----------+-----------------+------+| euny | Chang Eun-young | 99 || cavalist | Ryu Han Seung | 99 || netj | Jaeho Shin | 2000 |+----------+-----------------+------+3 rows in set (0.00 sec)
mysql> DELETE FROM Students -> WHERE sid='euny';Query OK, 1 row affected (0.00 sec)
mysql> UPDATE Students -> SET sid='asdf' -> WHERE sid='euny';Query OK, 1 row affected (0.00 sec)
mysql> SELECT * FROM Students;+----------+-----------------+------+| sid | sname | snum |+----------+-----------------+------+| asdf | Chang Eun-young | 99 || cavalist | Ryu Han Seung | 99 || netj | Jaeho Shin | 2000 |+----------+-----------------+------+1 row in set (0.00 sec)
mysql> SELECT * FROM Students ORDER BY sname;+----------+-----------------+------+| sid | sname | snum |+----------+-----------------+------+| asdf | Chang Eun-young | 99 || netj | Jaeho Shin | 2000 || cavalist | Ryu Han Seung | 99 |+----------+-----------------+------+3 rows in set (0.02 sec)
mysql> SELECT sname FROM Students WHERE snum=99;+-----------------+| sname |+-----------------+| Chang Eun-young || Ryu Han Seung |+-----------------+1 row in set (0.00 sec)
Using Connector/J
MySQL Connector/J is a native Java driver that converts JDBC (Java Database Connectivity) calls into the network protocol used by the mySQL database.
It lets developers working with the Java programming language easily build programs and applets that interact with MySQL and connect all corporate data, even in a heterogeneous environment.
MySQL Connector/J is a Type IV JDBC driver and has a complete JDBC feature set that supports the capabilities of MySQL.
Using Connector/J Download the software from http://dev.mysql.com/downloads/connector/j/5.0.html
MySQL Connector/J is distributed as a zip or .tar.gz archive containing the sources, the class files, and the JAR archive named mysql-connector-java-[version]-bin.jar
Install this file in C:\Program Files\Java\jdk1.5.0_07\jre\lib\
ext or similar directory on your machine
Accessing mySQL from a servlet<HTML><BODY><TITLE>See Account Information</TITLE>Enter account number to view:<BR><form action="StudentList" method="post"> <input name="account"> <input type="submit" name="submit"
value="submit"></form></BODY></HTML>
Accessing mySQL from a servletpackage dbpackage;import java.io.*;import java.sql.*;import javax.servlet.*;import javax.servlet.http.*;
public class StudentList extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html"); PrintWriter out = response.getWriter(); String docType = "<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 " + "Transitional//EN\"\
n"; String title = "Student List in mySQL"; out.print(docType + "<HTML>\n" + "<HEAD><TITLE>" + title + "</TITLE></HEAD>\n" + "<BODY BGCOLOR=\"#FDF5E6\"><CENTER>\n" + "<H1>Database Results</H1>\n");
Accessing mySQL from a servlet String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost/newdb"; String username = "ira"; String password = "mypassword"; String query = "SELECT * from student;"; showTable(driver, url, username, password, query, out); out.println("</CENTER></BODY></HTML>"); }
public void showTable(String driver, String url, String username, String password,
String query, PrintWriter out) { try { // Load database driver if it's not already loaded. Class.forName(driver); // Establish network connection to database. Connection connection = DriverManager.getConnection(url, username,
password); // Look up info about the database as a whole. DatabaseMetaData dbMetaData = connection.getMetaData(); out.println("<UL>"); String productName = dbMetaData.getDatabaseProductName(); String productVersion = dbMetaData.getDatabaseProductVersion(); out.println(" <LI><B>Database:</B> " + productName + " <LI><B>Version:</B> " + productVersion + "</UL>");
Accessing mySQL from a servletStatement statement = connection.createStatement(); // Send query to database and store results. ResultSet resultSet = statement.executeQuery(query); // Print results. out.println("<TABLE BORDER=1>"); ResultSetMetaData resultSetMetaData =
resultSet.getMetaData(); int columnCount = resultSetMetaData.getColumnCount(); out.println("<TR>"); // Column index starts at 1 (a la SQL), not 0 (a la Java). for(int i=1; i <= columnCount; i++) { out.print("<TH>" + resultSetMetaData.getColumnName(i)); } out.println(); // Step through each row in the result set. while(resultSet.next()) { out.println("<TR>"); // Step across the row, retrieving the data in each // column cell as a String.}
Accessing mySQL from a servletfor(int i=1; i <= columnCount; i++) { out.print("<TD>" + resultSet.getString(i)); } out.println(); } out.println("</TABLE>"); connection.close(); } catch(ClassNotFoundException cnfe) { System.err.println("Error loading driver: " + cnfe); } catch(SQLException sqle) { System.err.println("Error connecting: " + sqle); } catch(Exception ex) { System.err.println("Error with input: " + ex); } }
}
Accessing mySQL from a servletprivate static void showResults(ResultSet results) throws SQLException { while(results.next()) { System.out.print(results.getString(1) + " "); } System.out.println(); }
private static void printUsage() { System.out.println("Usage: PreparedStatements host " + "dbName username password " + "vendor [print]."); }
public void doPost(HttpServletRequest inRequest, HttpServletResponse outResponse)
throws ServletException, IOException { doGet(inRequest, outResponse); }