SQL ‐ CURD Operation - CloudScope/DevOpsWithCloudScope GitHub Wiki

1. Create (INSERT)

• Purpose: To add new records to a table.
• Syntax:

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

• Example:

  INSERT INTO employees (first_name, last_name, email)
  VALUES ('John', 'Doe', '[email protected]');
  

2. Read (SELECT)

• Purpose: To retrieve data from one or more tables.
• Syntax:

  SELECT column1, column2, ...
  FROM table_name
  WHERE condition;
  

• Example:

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

3. Update (UPDATE)

• Purpose: To modify existing records in a table.
• Syntax:

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

• Example:

  UPDATE employees
  SET email = '[email protected]'
  WHERE employee_id = 1;
  

4. Delete (DELETE)

• Purpose: To remove records from a table.
• Syntax:

  DELETE FROM table_name
  WHERE condition;
  

• Example:

  DELETE FROM employees
  WHERE employee_id = 1;
  

5. DISTINCT

• Purpose: The DISTINCT keyword is used to remove duplicate rows from the result set. It ensures that the results returned by a query contain only unique values.
• Syntax:

  SELECT DISTINCT column1, column2, ...
  FROM table_name;
  

• Example:

  SELECT DISTINCT city
  FROM customers;
  

  This query retrieves unique cities from the customers table.

6. PRINT

• Purpose: The PRINT statement is primarily used in SQL Server to display messages to the user. It's not part of standard SQL and is specific to certain database systems.
• Syntax:

  PRINT 'Your message here';
  

• Example:

  PRINT 'Query executed successfully!';
  

  This will output the message "Query executed successfully!" to the console.

7. IN

• Purpose: The IN operator allows you to specify multiple values in a WHERE clause. It is used to filter records based on a list of specified values.
• Syntax:

  SELECT column1, column2, ...
  FROM table_name
  WHERE column_name IN (value1, value2, ...);
  

• Example:

  SELECT *
  FROM products
  WHERE category IN ('Electronics', 'Apparel');
  

  This query retrieves all products that belong to either the "Electronics" or "Apparel" categories.

8. WHERE

• Purpose: The WHERE clause is used to filter records based on specified conditions. It restricts the rows returned by a SELECT, UPDATE, or DELETE statement.
• Syntax:

  SELECT column1, column2, ...
  FROM table_name
  WHERE condition;
  

• Example:

  SELECT *
  FROM employees
  WHERE salary > 50000;
  

  This query retrieves all employees with a salary greater than 50,000.

Combining Keywords

You can combine these keywords to create more complex queries. Here’s an example that combines DISTINCT, WHERE, and IN:

SELECT DISTINCT city
FROM customers
WHERE country IN ('USA', 'Canada');