Common SQL commands with example

Certainly! SQL (Structured Query Language) is used to interact with relational databases. Here are some common SQL commands with examples:

SELECT:

The SELECT statement is used to query the database and retrieve data.

   SELECT column1, column2 FROM table_name WHERE condition;

Example:

   SELECT first_name, last_name FROM employees WHERE department = 'IT';

INSERT:

The INSERT statement is used to insert new records into a table.

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

Example:

   INSERT INTO customers (first_name, last_name, email) VALUES ('John', 'Doe', 'john.doe@example.com');

UPDATE:

The UPDATE statement is used to modify existing records in a table.

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

Example:

   UPDATE products SET price = 25.99 WHERE product_id = 101;

DELETE:

The DELETE statement is used to delete records from a table.

   DELETE FROM table_name WHERE condition;

Example:

   DELETE FROM customers WHERE last_purchase_date < '2022-01-01';

CREATE TABLE:

The CREATE TABLE statement is used to create a new table.

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

Example:

   CREATE TABLE employees (
       employee_id INT PRIMARY KEY,
       first_name VARCHAR(50),
       last_name VARCHAR(50),
       department VARCHAR(50)
   );

ALTER TABLE:

The ALTER TABLE statement is used to modify an existing table (e.g., add or drop columns).

   ALTER TABLE table_name
   ADD column_name datatype;

   ALTER TABLE table_name
   DROP COLUMN column_name;

Example:

   ALTER TABLE employees
   ADD hire_date DATE;

   ALTER TABLE employees
   DROP COLUMN phone_number;

DROP TABLE:

The DROP TABLE statement is used to delete an existing table and all its data.

   DROP TABLE table_name;

Example:

   DROP TABLE customers;

JOIN:

The JOIN operation is used to combine rows from two or more tables based on a related column between them.

   SELECT * FROM table1
   INNER JOIN table2 ON table1.column_name = table2.column_name;

Example:

   SELECT orders.order_id, customers.first_name, customers.last_name
   FROM orders
   INNER JOIN customers ON orders.customer_id = customers.customer_id;

These are just a few examples of common SQL commands. SQL is a powerful language with many features, and its usage can vary depending on the specific database system you are working with (e.g., MySQL, PostgreSQL, SQLite, SQL Server).

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