当执行查询时,ORACLE采用了内部的操作. 下表显示了几种重要的内部操作.
|
ORACLE Clause |
内部操作 |
|
ORDER BY |
SORT ORDER BY |
|
UNION |
UNION-ALL |
|
MINUS |
MINUS |
|
INTERSECT |
INTERSECT |
|
DISTINCT,MINUS,INTERSECT,UNION |
SORT UNIQUE |
|
MIN,MAX,COUNT |
SORT AGGREGATE |
|
GROUP BY |
SORT GROUP BY |
|
ROWNUM |
COUNT or COUNT STOPKEY |
|
Queries involving Joins |
SORT JOIN,MERGE JOIN,NESTED LOOPS |
|
CONNECT BY |
CONNECT BY |