Issue and solution

This only applies when you are trying to use native sql instead of querydsl and forcing fields into a pure sql query. The types of entity’s fields need to be considered whether they match the constraints of the DB you are using.

The field type that I was trying to get and insert by performing outer joining does not seem to match with the field im trying to select. I double checked the column constraint but both were NUMBER (10,0).

Turns out the field in that table was Long while mine was Integer.

If the error is not still fixed

Even if you cast to an explicit type and still get this error, it is possible your database schema is the problem. For me, I declared my database column as NUMBER but my JPA entity is an Integer. Actually number also accepts Integer but im not sure why there was this error. So I deleted the table and created a fresh new table that accepts

“RELAY_SUCCESS_COUNT INTEGER”

I think it is probably cuz if you allowed JPA to create the database schema automatically and not put ddl as none, then this problem would not have occurred. But since I was using native SQL, this problem arised.