Aggregate functions like MAX(), COUNT() are NOT passed across the net but rather are performed on the local node.
: MAX(),COUNT() 같은 집계함수는 원격에서 수행되지 않고, 로컬로 데이타를 복사하여 수행됩니다.
Expressions in the SELECT list are decomposed into columns and evaluated when the data is retrieved.
: SELECT 리스트로 표현되는 것은 컬럼단위로 측정되어 되돌아 오는 것이다.
Only a relevant subset of columns are fetched across the net.
: 컬럼의 서브셋만이 패치(fetch)될 수 있다.
An expression in a WHERE clause is passed across to the remote database if it compares the remote column to a literal (eg ename = 'KING').
: WHERE 절에있는 표현식에서 원격의 리터럴 컬럼과 비교한다면 원격 데이터베이스를 통해서 전달한다. (예) ename='KING'
Expressions in a WHERE clause are passed to the remote database if all columns are in the expression are located in the same remote table the remote database (eg emp.sal * 0.20 > emp.bonus)
Datatype conversion functions like TO_CHAR() in a WHERE clause are subject to the conditions in #4 and #5.
The optimizer only has knowledge of local indexes when making decisions about how to execute a query.
Remote indexes can be still be used to resolve the decomposed query sent to the remote database.
GROUP BY is not sent to the remote database.
: GROUP BY 는 원격디비에서 계산되지 않는다
ORDER BY is not sent to the remote database.
: ORDER BY 는 원격디비에서 계산되지 않는다