Handling NULL Values and Built-in Functions Null values and built-in functions play a crucial role in data management and SQL queries. They allow you to hand...
Null values and built-in functions play a crucial role in data management and SQL queries. They allow you to handle missing or unknown data points while still performing calculations and comparisons on the entire dataset.
Missing Values:
NULL is used to represent a missing or unknown value. It is not a value itself, but rather a marker that indicates the absence of a data point.
When a value is NULL, it will be ignored during calculations and comparisons.
For example, the following query returns all the customers from the 'customers' table where the 'country' column is NULL:
sql
SELECT * FROM customers WHERE country IS NULL;
Built-in Functions for Handling NULL:
IS NULL: This function checks if a value is NULL.
IS NOT NULL: This function checks if a value is not NULL.
IS EMPTY: This function checks if a value is empty string (an empty space or null string).
IS BLANK: This function checks if a value is an empty string or null string.
Using Built-in Functions with NULL:
sql
SELECT * FROM customers WHERE country IS NULL OR city = '';
Additional Notes:
NULL values can be assigned values, but it is recommended to avoid assigning values directly to NULL fields.
NULL values can be used in WHERE clauses and used in various ways within queries.
Understanding null values and built-in functions will significantly improve your data handling and SQL skills