How to Write SQL Query with Multiple Where Condition
Writing SQL queries with multiple WHERE conditions can be a challenging task, especially for beginners. However, understanding how to construct such queries is crucial for efficient data retrieval and manipulation. In this article, we will discuss the basics of writing SQL queries with multiple WHERE conditions and provide some practical examples to help you master this skill.
Understanding WHERE Clauses
The WHERE clause is used to filter records from a database table based on specified conditions. When you want to retrieve data that meets multiple criteria, you can use multiple WHERE conditions in your query. These conditions are combined using logical operators such as AND, OR, and NOT.
Using AND Operator
The AND operator is used to combine two or more conditions, and the query will return results that satisfy all the conditions. For example, consider the following query:
“`sql
SELECT FROM employees
WHERE department = ‘Sales’ AND salary > 50000;
“`
In this query, we are selecting all records from the “employees” table where the department is ‘Sales’ and the salary is greater than 50000.
Using OR Operator
The OR operator is used to combine two or more conditions, and the query will return results that satisfy at least one of the conditions. For example:
“`sql
SELECT FROM products
WHERE category = ‘Electronics’ OR category = ‘Books’;
“`
This query will return all records from the “products” table where the category is either ‘Electronics’ or ‘Books’.
Using NOT Operator
The NOT operator is used to negate a condition, and the query will return results that do not satisfy the specified condition. For example:
“`sql
SELECT FROM customers
WHERE NOT status = ‘Inactive’;
“`
In this query, we are selecting all records from the “customers” table where the status is not ‘Inactive’.
Combining AND, OR, and NOT Operators
You can combine AND, OR, and NOT operators to create complex queries that meet specific requirements. For example:
“`sql
SELECT FROM orders
WHERE (status = ‘Shipped’ OR status = ‘Delivered’) AND (order_date BETWEEN ‘2021-01-01’ AND ‘2021-12-31’);
“`
This query will return all records from the “orders” table where the status is either ‘Shipped’ or ‘Delivered’, and the order date is between January 1, 2021, and December 31, 2021.
Conclusion
Writing SQL queries with multiple WHERE conditions can be a powerful tool for data retrieval and manipulation. By understanding how to use AND, OR, and NOT operators, you can create complex queries that meet your specific requirements. Practice with various examples and scenarios will help you become proficient in constructing efficient and effective SQL queries.
