oracle practical tutorial

Oracle is one of the most famous relational database management systems in the world. It provides a simple, fast and secure way to store and manage various types of data. This article aims to introduce readers to practical tutorials on Oracle database and help beginners understand the basic operations and usage skills of Oracle database.

1. Preparation work

Before using Oracle database, you need to complete the following steps:

1.1. Download and install Oracle database

You can download the latest version of the Oracle database from the Oracle official website, and then follow the steps in the official guide to install it.

1.2. Create a user

Before using the Oracle database, you need to create a user for yourself. You can use the following SQL statement to create a user:

CREATE USER user_name IDENTIFIED BY password;

Where "user_name" is the user name you want to create, and "password" is the user you want to create Password set.

1.3. Grant permissions

Before using the database, you need to assign the required permissions to your users. You can use the following SQL statement to assign permissions to a user:

GRANT permission TO user_name;

where "permission" is the permission you want to assign to the user, and "user_name" is the permission you want to assign username.

2. Basic database operations

2.1. Create database

You can use the following SQL statement to create a database:

CREATE DATABASE database_name ;

Where "database_name" is the name of the database you want to create.

2.2. Display the database list

You can display the database list using the following SQL statement:

SHOW DATABASES;

This will display all available database lists .

2.3. Using a database

When you want to use a database, you need to use the following SQL statement:

USE database_name;

Where, " database_name" is the name of the database you want to use.

2.4. Create tables

In a database, you can create tables to store different types of data. The following is an example of a SQL statement to create a table:

CREATE TABLE table_name (
column1 datatype,
column2 datatype,
column3 datatype,
....
);

Among them, "table_name" is the name of the table you want to create, "column1", "column2", etc. are the names of the columns you want to create, and "datatype" is the data type you want to choose for the column. .

2.5. Displaying a list of tables

You can display a list of tables using the following SQL statement:

SHOW TABLES;

This will display a list of all available tables .

2.6. Inserting data

Inserting data into a table is a basic database operation. The following is an example of a SQL statement to insert data:

INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);

Among them, "table_name" is the name of the table into which you want to insert data, "column1", "column2", etc. are the names of the columns into which you want to insert values, and "value1", "value2", etc. are the values ​​you want to insert.

2.7. Update data

You can use the following SQL statement to update the data in the table:

UPDATE table_name
SET column1 = value1, column2 = value2, .. .
WHERE condition;

Among them, "table_name" is the name of the table you want to update, "column1", "column2", etc. are the names of the columns you want to update, "value1", "value2" " etc. are the values ​​you want to update, and "condition" is the update condition.

2.8. Delete data

The following is an example of a SQL statement to delete data in a table:

DELETE FROM table_name WHERE condition;

Where, "table_name ” is the name of the table from which you want to delete data, and “condition” is the deletion condition.

3. Data Query

3.1. Basic Query

Basic query allows you to retrieve data from a table. The following is an example of a basic query SQL statement:

SELECT column1, column2, ... FROM table_name;

Among them, "column1", "column2", etc. are the columns you want to query Name, "table_name" is the name of the table you want to query.

3.2. Conditional query

Conditional query allows you to retrieve data based on conditions. The following is an example of a conditional query SQL statement:

SELECT column1, column2, ...
FROM table_name
WHERE condition;

Among them, "table_name" is the parameter you want to query The name of the table, "condition" is the query condition.

3.3. Sort query

Sort query allows you to retrieve data in a specific order. The following is an example of a SQL statement for a sorting query:

SELECT column1, column2, ...
FROM table_name
ORDER BY column_name ASC/DESC;

Where, "table_name" is the name of the table you want to query, "column_name" is the name of the column you want to sort by, "ASC" means ascending order, and "DESC" means descending order.

3.4. Group query

Group query allows you to group and aggregate data based on specific conditions. The following is an example of a SQL statement for a group query:

SELECT column1, aggregate_function(column2)
FROM table_name
GROUP BY column1;

Where "table_name" is the name of the table you want to query, "column1" is the column you want to group by, and "aggregate_function" is the aggregate function you want to apply.

4. Application Integration

Oracle Database also provides an easy way to integrate it with applications. The following is an example of using Java to write code to access an Oracle database:

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class OracleExample {

public static void main(String[] args) {

Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
  String userName = "your_user_name";
  String password = "your_password";
  String url = "jdbc:oracle:thin:@localhost:1521:ORCL";
  Class.forName("oracle.jdbc.driver.OracleDriver");
  conn = DriverManager.getConnection(url, userName, password);
  stmt = conn.createStatement();
  rs = stmt.executeQuery("SELECT * FROM table_name");
  while (rs.next()) {
    System.out.println(rs.getString("column1") + ", " + rs.getString("column2"));
  }
} catch (ClassNotFoundException e) {
  e.printStackTrace();
} catch (SQLException e) {
  e.printStackTrace();
} finally {
  try {
    rs.close();
    stmt.close();
    conn.close();
  } catch (SQLException e) {
    e.printStackTrace();
  }
}

}
}

In the above example, "your_user_name" and "your_password" are the username and password of your Oracle user, and "jdbc:oracle:thin:@localhost:1521:ORCL" is the Oracle The connection string of the database, "table_name" is the name of the table you want to query.

Conclusion

Oracle is a powerful relational database management system that is suitable for various types of data storage and management. This article provides some basic Oracle database operation and usage skills, hoping to help beginners better master the Oracle database.

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