How to return results only if value exists in SQL?

Problem

You have a table with a column where some rows contain NULL values or empty strings. You want to retrieve rows where this column has a value (i.e., not NULL and not an empty string).

Input

product_id	product_name	product_description
1	Laptop	High performance gaming laptop
2	Mouse
3	Keyboard
4	Monitor	27 inch 4K display

Create Input Table: Gist

Desired Output

product_id	product_name	product_description
1	Laptop	High performance gaming laptop
4	Monitor	27 inch 4K display

Solution 1:

Using WHERE

SELECT * 
FROM Products 
WHERE product_description IS NOT NULL AND product_description != '';

Explanation:

• product_description IS NOT NULL filters out the rows where the product_description is NULL.

• product_description != ” filters out the rows where the product_description is an empty string.

Combining these conditions with an AND operator ensures that you retrieve rows where product_description has a value.

Solution 2:

Using COALESCE

SELECT * 
FROM Products 
WHERE COALESCE(product_description, '') <> ''
 DESC;

Explanation:

The COALESCE function returns the first non-NULL value in its list of arguments. By using COALESCE(product_description, ”), if product_description is NULL, it will be replaced by an empty string.

The condition <> ” then filters out both NULLs (which have been converted to empty strings by COALESCE) and actual empty strings

.
This method uses a single condition instead of two, which can be considered more concise in some scenario
s.

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