SQL WHERE CASE 子句中的表达式

Question

I want to fetch data from a table Item that has the two fields name and nullable_name , the second one can be empty.

Now I want to add a filter string, so that only results will get fetched that contain that string (in the name field if nullable_name is null, and in the nullable_name field if it is present). So I want one of two WHERE expressions to take place, depending on the situation.

What I tried but didn't work:

SELECT * FROM Item
WHERE
CASE 
    WHEN Item.nullable_name IS NULL THEN (Item.name LIKE '%filter%')
    ELSE (Item.nullable_name LIKE '%filter%')
END

Answer 1

You seem to want coalesce() :

where coalesce(item.nullable_name, item.name) like '%filter%'

coalesce() is a function that returns the first non- NULL value.

Answer 2

Try Where isnull(item.nullable_name, item.name) like '%filter%'