sql query with multiple where statements

If you're wondering how to write an SQL query with multiple WHERE statements, the key is understanding how to combine multiple conditions properly in a single WHERE clause.

In SQL, you don’t use multiple separate WHERE keywords; instead, you combine several conditions within one WHERE clause using logical operators like AND, OR, and sometimes NOT.

How to use multiple conditions in WHERE:

• Use AND to require all conditions to be true.
  
• Use OR to allow any one of the conditions to be true.
  
• Combine AND and OR carefully with parentheses to control the logic.
  

Example:

Suppose you want to select employees who work in the 'Sales' department and have a salary greater than 50000:

SELECT * FROM employees
WHERE department = 'Sales' AND salary > 50000;

If you want employees who work in 'Sales' or 'Marketing':

SELECT * FROM employees
WHERE department = 'Sales' OR department = 'Marketing';

You can combine multiple conditions like this:

SELECT * FROM employees
WHERE (department = 'Sales' OR department = 'Marketing') AND salary > 50000;

Tips:

• Use parentheses to group conditions and make your intent clear.
  
• Remember that AND has higher precedence than OR, so parentheses help avoid logic errors.
  
• You can also use other operators like <, >, IN, BETWEEN in your WHERE conditions.
  

Summary:

• Multiple WHERE conditions are combined inside a single WHERE clause.
  
• Use AND and OR to control how conditions interact.
  
• Parentheses are important for complex logical expressions.