When you confirm the data of nUser ID from TB_EVENT_LOG, some user ID could be "-" at the front of the user ID.
If User ID is more than 2147483647, the nUserID of TB_EVENT_LOG will be minus at the front of the number.
It is because the data type is different.
: nUserID of TB_EVENT_LOG table can be -2,147,483,648 ~ 2,147,483,647. (Signed integer type)
: sUserID of TB_USER table can be 0 ~ 4294967295 .
Please refer the following query to change the data type.
If you would like to confirm that nEventIdn is 27, you have to use the below query.
select nEventIDn, nUSerID, CAST(CAST(nUserID AS BINARY) AS bigint) from TB_EVENT_LOG where nEventIdn = 217;
For your reference, I've attached the table structure.