9+ Sql With 使い方 References
Introduction to SQL
SQL, or Structured Query Language, is a programming language that is used to manage and manipulate databases. It is used to create, modify, and delete data in a database. SQL is used in many industries, including finance, healthcare, and technology. In this article, we'll explore the basics of SQL and how it can be used.Why Learn SQL?
SQL is an important language to learn for a variety of reasons. It is widely used in the industry, making it a valuable skill to have. Additionally, SQL allows you to manage and manipulate data in a relational database, which is an essential skill for anyone working with data.Getting Started with SQL
To get started with SQL, you'll need to have access to a database management system (DBMS) like MySQL, Oracle, or Microsoft SQL Server. Once you have access to a DBMS, you can start creating and manipulating data.The Basics of SQL
Creating a Database
To create a database in SQL, you'll need to use the CREATE DATABASE statement. This statement creates a new database with the specified name.CREATE DATABASE mydatabase;
Creating a Table
After you've created a database, you'll need to create a table to store your data. To create a table in SQL, you'll need to use the CREATE TABLE statement. This statement creates a new table with the specified columns.CREATE TABLE customers (id INT, name VARCHAR(255), email VARCHAR(255));
Inserting Data
Once you've created a table, you can insert data into it using the INSERT INTO statement. This statement adds a new row to the table with the specified values.INSERT INTO customers (id, name, email) VALUES (1, 'John Doe', 'john.doe@example.com');
Updating Data
To update data in SQL, you'll need to use the UPDATE statement. This statement modifies existing data in a table.UPDATE customers SET name='Jane Doe' WHERE id=1;
Deleting Data
To delete data in SQL, you'll need to use the DELETE statement. This statement removes data from a table.DELETE FROM customers WHERE id=1;
Advanced SQL
Joining Tables
In SQL, you can use the JOIN statement to combine data from multiple tables. This is useful when you need to retrieve data that is spread across multiple tables.SELECT * FROM customers JOIN orders ON customers.id = orders.customer_id;
Grouping Data
To group data in SQL, you'll need to use the GROUP BY statement. This statement groups data based on a specified column.SELECT COUNT(*) as num_orders, customer_id FROM orders GROUP BY customer_id;
Ordering Data
To order data in SQL, you'll need to use the ORDER BY statement. This statement sorts data based on a specified column.SELECT * FROM customers ORDER BY name ASC;
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