SQL SQL Tutorial SQL Database



SQL In

Structured Query Language (SQL) is a programming language used to manage and manipulate relational databases. It is a standard language used by most relational database management systems (RDBMS) such as MySQL, Oracle, Microsoft SQL Server, and PostgreSQL. SQL is used to create, modify, and delete databases, tables, and data within those tables. It is also used to retrieve data from databases using queries.

SQL is a declarative language, which means that you tell the database what you want to do, and it figures out how to do it. This is different from procedural languages like Java or Python, where you tell the computer how to do something step-by-step.

Basic SQL Syntax

The basic syntax of SQL consists of a few keywords and clauses:

  • SELECT: used to retrieve data from one or more tables
  • FROM: specifies the table(s) to retrieve data from
  • WHERE: filters the data based on a condition
  • INSERT INTO: adds new data to a table
  • UPDATE: modifies existing data in a table
  • DELETE FROM: removes data from a table

Here are some examples of SQL queries:

<?php
// Connect to the database
$conn = mysqli_connect("localhost", "username", "password", "database");

// Retrieve all data from the "users" table
$result = mysqli_query($conn, "SELECT * FROM users");

// Loop through the results and display them
while ($row = mysqli_fetch_assoc($result)) {
  echo $row['name'] . " - " . $row['email'] . "<br>";
}

// Insert a new user into the "users" table
mysqli_query($conn, "INSERT INTO users (name, email) VALUES ('John Doe', 'john@example.com')");

// Update the email address of a user in the "users" table
mysqli_query($conn, "UPDATE users SET email='jane@example.com' WHERE name='Jane Doe'");

// Delete a user from the "users" table
mysqli_query($conn, "DELETE FROM users WHERE name='John Doe'");
?>

Conclusion

SQL is a powerful language used to manage and manipulate relational databases. It is a standard language used by most RDBMS and is essential for anyone working with databases. By understanding the basic syntax of SQL, you can create, modify, and delete databases, tables, and data within those tables.

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