nested mysql case when - mysql

Question

SELECT ( CASE
WHEN 1944.0000 >= country_from_price
AND 1944.0000 <= country_to_price
THEN ((1944.0000 + ((1944.0000 * country_percentage)/100)))
ELSE 1944.0000
END
)
FROM `country_markup`
WHERE estatus = '1'
AND country_id REGEXP '[[:<:]]138[[:>:]]'
Above query return value increased by percent but if condition is not full fill than it return NULL. What i want is if query return NULL value than it should return 1944.0000
and For this i have tried below code but did not get any success
SELECT IF( (SELECT (CASE
WHEN 1944.0000 >= country_from_price
AND 1944.0000 <= country_to_price
THEN ((1944.0000 + ((1944.0000 * country_percentage)/100)))
ELSE 1944.0000
END
) as f1
FROM `country_markup`
WHERE estatus = '1'
AND country_id REGEXP '[[:<:]]223[[:>:]]') IS NOT NULL, f1 ,1944.0000) as final_price
Thanks in advance

Answer 1

This appears to work with COALESCE (assuming your original query can only return a single record):
SELECT COALESCE((
SELECT
CASE WHEN 1944.0000 >= country_from_price AND 1944.0000 <= country_to_price
THEN ((1944.0000 + ((1944.0000 * country_percentage)/100)))
ELSE 1944.0000
END
FROM `country_markup`
WHERE estatus = '1'
AND country_id REGEXP '[[:<:]]138[[:>:]]'), 1944.0000) final_price
SQL Fiddle Demo
You can add LIMIT 1 to your subquery to make sure it only returns a single record as well if needed.
Here's an alternative using the MAX aggregate with COALESCE:
SELECT
COALESCE(MAX( CASE WHEN 1944.0000 >= country_from_price AND 1944.0000 <= country_to_price
THEN ((1944.0000 + ((1944.0000 * country_percentage)/100)))
ELSE 1944.0000
END ),1944.0000) final_price
FROM `country_markup`
WHERE estatus = '1'
AND country_id REGEXP '[[:<:]]138[[:>:]]'
More Fiddle

Answer 2

You just need to test that the country_percentage is not null in your expression:
SELECT (CASE WHEN 1944.0000 between country_from_price AND country_to_price and
country_percentage is not null
THEN ((1944.0000 + ((1944.0000 * country_percentage)/100)))
ELSE 1944.0000
END)
FROM `country_markup`
WHERE estatus = '1' AND country_id REGEXP '[[:<:]]138[[:>:]]';
I also changed the comparison logic to use between.