Best way to check for "empty or null value"

A tale of two string types

SQL offers multiple string types, and when checking for NULL or empty, the type of string considerable influences the approach. Let's dive into each:

Plain old equality

This is the straightforward way and works well for non-padded types like text and varchar:

SELECT *
FROM your_table
WHERE (your_column = '') IS NOT FALSE;


The IS NOT FALSE returns true for NULL or empty strings, and false for strings full of spaces or containing characters.

The double negative

For cases where you want to check for non-empty and non-null strings:

SELECT *
FROM your_table
WHERE (your_column <> '') IS NOT TRUE;


In other words, the above code tells SQL to return data only when your_column has some actual content, not just air! 🌬️

Length check deluxe

Particularly for char(n) types where whitespaces may throw off the balance:

SELECT *
FROM your_table
WHERE LENGTH(TRIM(COALESCE(your_column, ''))) > 0;


This trims any leading or trailing spaces, filters NULL values, and returns TRUE only for strings of positive length.

Advanced trickery for performance and integrity

Crafting SQL checks to handle NULL or EMPTY values might seem straightforward, but some advanced techniques can further optimize your queries:

Using NULL conditions efficiently

Leverage the benefit of indexing to fast-track NULL condition evaluations:

SELECT *
FROM your_table
WHERE your_column IS NOT NULL AND your_column <> '';


SQL servers love to hang around with indexed columns, making them super fast! 🏎️

Combining COALESCE and TRIM

Preserve data integrity while keeping your queries efficient:

SELECT *
FROM your_table
WHERE COALESCE(TRIM(your_column), 'placeholder') <> 'placeholder';


The TRIM and COALESCE function duo gives leading/trailing spaces and null values a firm handshake goodbye before the query execution. 🤝

Be brief, be smart

Avoid checking the same value twice. Instead of a lengthy value IS NULL OR value = '', turn on your SQL efficiency mode:

SELECT *
FROM your_table
WHERE COALESCE(NULLIF(your_column, ''), '') <> '';


The code above packs fiercely coded compactness and strict precision! 🥊

Play it safe with SQL's evaluation

If your SQL engine short-circuits logical operations (stops evaluating as soon as the outcome is determined), then form your conditions to take advantage of it for faster checks.

Going the extra mile

Compound (but not confusing!) checks

For those complex days when you need to cover all bases:

SELECT *
FROM your_table
WHERE COALESCE(NULLIF(TRIM(your_column), ''), 'non_empty_string') <> 'non_empty_string';


Perfect for those "I want absolutely no emptiness or nullness, and oh, remove the darn spaces" kind of days!

Understanding your strings

The choice of method very much depends on the nature of your string - think before you choose your SQL weaponry!

In the function jungle

Some of us scroll through Stackoverflow; others go wild in the SQL functions jungle. Know your functions, know their strengths, your query will thank you! (And maybe your DBA, too...)