CRUD (short for Create, Read, Update, and Delete) operations are the four fundamental actions performed on data in a relational database using SQL.

Here are the standard SQL commands for each operation, assuming you have a table named Employees with columns EmployeeID, Name, and Department.

1. Inserting Records (C-reate Operation)

The INSERT INTO command is used to add new rows (records) to a table.

Syntax:

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

Example:

INSERT INTO Employees (EmployeeID, Name, Department)
VALUES (101, 'Alice Smith', 'Sales');

2. Selecting/Retrieving Records (R-ead Operation)

The SELECT command is used to retrieve data from a table or a set of tables. This is the most frequently used command.

Syntax:

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

The WHERE clause is optional but crucial for filtering results.

Example:

-- Retrieve all columns and all rows
SELECT *
FROM Employees;

-- Retrieve specific columns for employees in the 'Sales' department
SELECT Name, EmployeeID
FROM Employees
WHERE Department = 'Sales';

3. Updating Records (U-pdate Operation)

The UPDATE command is used to modify existing data in one or more rows of a table.
Crucial Note: Always use the WHERE clause with UPDATE. If you omit it, all rows in the table will be updated.

Syntax:

UPDATE table_name 
SET column1 = new_value1, column2 = new_value2, ... 
WHERE condition;

Example:

-- Change the department of the employee with `EmployeeID = 101`
UPDATE Employees
SET Department = 'Marketing'
WHERE EmployeeID = 101;

4. Deleting Records (D-elete Operation)

The DELETE FROM command is used to remove one or more rows from a table.
Crucial Note: Similar to UPDATE, always use the WHERE clause with DELETE FROM. If you omit it, all rows in the table will be deleted.

Syntax:

DELETE FROM table_name WHERE condition;

Example:

-- remove the employee with `EmployeeID = 101`
DELETE FROM Employees
WHERE EmployeeID = 101;