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SQL Syntax

SQL (Structured Query Language) is a programming language used for managing and manipulating relational databases. Here's a basic overview of its syntax:


  1. SELECT: Used to retrieve data from a database.

SELECT column1, column2 FROM table_name WHERE condition;


Example


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




  1. INSERT INTO: Used to insert new records into a table.

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


Example


INSERT INTO employees (first_name, last_name) VALUES ('John', 'Doe');



  1. UPDATE: Used to modify existing records in a table.

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


Example


UPDATE employees SET department = 'Finance' WHERE employee_id = 101;


  1. DELETE: Used to delete records from a table.

DELETE FROM table_name WHERE condition;


Example


DELETE FROM employee WHERE employee_id=102;


  1. CREATE TABLE: Used to create a new table in the database.

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) );



  1. ALTER TABLE: Used to modify an existing table.

ALTER TABLE table_name ADD column_name datatype;


Example


ALTER TABLE employees ADD email VARCHAR(100);



  1. DROP TABLE: Used to delete a table and all its data from the database.

DROP TABLE table_name;


Example


DROP TABLE table_name;



  1. JOIN: Used to combine rows from two or more tables based on a related column.

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



Example


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




  1. GROUP BY: Used to group rows that have the same values into summary rows.

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


Example


SELECT product_id, SUM(quantity) AS total_quantity FROM orders GROUP BY product_id;



  1. ORDER BY: Used to sort the result set in ascending or descending order.

SELECT * FROM table_name ORDER BY column_name ASC|DESC;


Example


SELECT * FROM customers ORDER BY last_name ASC;



These are some of the fundamental SQL commands and their syntax. The exact syntax may vary slightly depending on the database management system you are using (e.g., MySQL, PostgreSQL, SQLite, etc.), so it's always a good idea to consult the documentation specific to your database.

 

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