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Welcome to SQL 101, an introductory guide to Structured Query Language (SQL). SQL is a programming language designed specifically for managing data held in relational database systems. Even if you have no prior coding experience, SQL is a great language to start with, due to its straightforward syntax and widespread usage. In this guide, we will provide some basic SQL operations with examples.
Creating a Table
The CREATE TABLE statement is used to create a new table in SQL. Here is a basic example:
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CREATE TABLE customers ( id INT PRIMARY KEY, name VARCHAR(100), email VARCHAR(100) ); |
This will create a new table named “customers”, with three fields: “id”, “name”, and “email”. The data types of these fields are INT (integer) and VARCHAR (string), respectively.
Inserting Data
Once we have a table, we can insert data into it using the INSERT INTO statement. Here’s how:
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INSERT INTO customers (id, name, email) VALUES (1, 'John Doe', <a href="mailto:'john.doe@example.com'" >'john.doe@example.com'</a>); |
This will insert a new record into the “customers” table, with ID as 1, name as ‘John Doe’, and email as ‘john.doe@example.com’.
Querying Data
The SELECT statement is used to select data from a database. The data returned is stored in a result table, called the result-set. If you want to select all the fields available in the table, use the following SQL:
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SELECT * FROM customers; |
If you want to select just some of the fields, you will need to specify them, like so:
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SELECT name, email FROM customers; |
This will return a table with the ‘name’ and ’email’ fields of all records in the “customers” table.
Updating Data
The UPDATE statement is used to update existing records in a table. Here’s how to change the name of the customer with id 1 to ‘Jane Doe’:
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UPDATE customers SET name = 'Jane Doe' WHERE id = 1; |
This command updates the ‘name’ field to ‘Jane Doe’ for the record in the ‘customers’ table where ‘id’ equals 1.
Deleting Data
The DELETE statement is used to delete existing records in a table. Here’s how to delete the customer with id 1:
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DELETE FROM customers WHERE id = 1; |
This command deletes the record from the ‘customers’ table where ‘id’ equals 1.
Conclusion
In this guide, we’ve covered some of the most basic SQL operations. With just these commands, there’s already a lot you can do. We have a rich variety of resources to help you take the next steps in your SQL journey, don’t stop here! As an SQL computer programmer, remember each day is a learning process and there’s always something new to learn. Happy coding!