Case Statement with comparison - mysql

Question

In the existing statement below I am comparing the host_name and ip_adress with records retrieved from an other table and mark the column as true when found, but I would like to tweak it to give a true result when the host_name is also a part of identifer from the record retrieved
i.e
host_name=abc
identifier=abc.google.com should also be true
CASE
WHEN
(
(`inv_y`.`host_name` <> '')
AND
`inv_y`.`host_name` IN (SELECT `inv_x`.`identifier`
FROM `inv_x`
ORDER BY `inv_x`.`creation_date` DESC
)
)
OR
(
(`inv_y`.`ip_address` <> '')
AND
inv_y`.`ip_address` IN (SELECT `inv_x`.`identifier`
FROM `inv_x`
ORDER BY `inv_x`.`creation_date` DESC
)
)
THEN
'True'
ELSE
'False'
END

Answer 1

It looks like you could benefit from the EXISTS function. Something like the following could work:
SELECT CASE WHEN EXISTS(SELECT 1
FROM inv_y
WHERE (ip IN (SELECT identifier
FROM inv_x)
OR hostname IN (SELECT identifier
FROM inv_x))
AND hostname LIKE '%eb%'
) = 1 THEN "True"
ELSE "False"
END AS Present;
Here's a demo of this working: SQL Fiddle
Note, the above could be simplified further if you can work with a 1 or 0 instead of true or false. EXISTS returns a 1 if the row is found, and 0 if not, and the CASE is there simply to translate this into 'True' or 'False', so you could simply have the following:
SELECT EXISTS(SELECT 1
FROM inv_y
WHERE (ip IN (SELECT identifier
FROM inv_x)
OR hostname IN (SELECT identifier
FROM inv_x)
)
AND hostname LIKE '%eb%') AS Present;