我正在学习如何将GROUP BY子句与Oracle Database 12c SQL一起使用。 我想知道当你需要在子句中列出多个列时，在GROUP BY子句中列出列的顺序是否会影响最终结果。
为了证明我的意思，我将使用这个样本表，BOOKSHELF：
+--------------------------------------------------------------------------------------------------------------------------------------------------------+
| TITLE PUBLISHER CATEGORY_NAME RATING |
+--------------------------------------------------------------------------------------------------------------------------------------------------------+
| ---------------------------------------------------------------------------------------------------- -------------------- -------------------- ------ |
| To Kill A Mockingbird Harper Collins ADULTFIC 5 |
| Wonderful Life W.W. Norton ADULTNF 5 |
| Innumeracy Vintage Books ADULTNF 4 |
| Kierkegaard Anthology Princeton Univ Pr ADULTREF 3 |
| Anne Of Green Gables Grammercy CHILDRENFIC 3 |
| Good Dog, Carl Little Simon CHILDRENPIC 1 |
| Letters And Papers From Prison Scribner ADULTNF 4 |
| The Discoverers Random House ADULTNF 4 |
| The Mismeasure Of Man W.W. Norton ADULTNF 5 |
| Either/Or Penguin ADULTREF 3 |
| Polar Express Houghton Mifflin CHILDRENPIC 1 |
| Runaway Bunny Harper Festival CHILDRENPIC 1 |
| My Ledger Bryla Press ADULTNF 5 |
| Complete Poems Of John Keats Viking ADULTREF 2 |
| Under The Eye Of The Clock Arcade Pub CHILDRENNF 3 |
| John Adams Simon Schuster ADULTNF 4 |
| Truman Simon Schuster ADULTNF 4 |
| Journals Of Lewis And Clark Mariner ADULTNF 4 |
| Gospel Picador ADULTFIC 4 |
| Emma Who Saved My Life St Martin'S Press ADULTFIC 3 |
| Midnight Magic Scholastic CHILDRENFIC 1 |
| Harry Potter And The Goblet Of Fire Scholastic CHILDRENFIC 4 |
| Shoeless Joe Mariner ADULTFIC 3 |
| Box Socials Ballantine ADULTFIC 3 |
| Trumpet Of The Swan Harper Collins CHILDRENFIC 3 |
| Charlotte's Web Harper Trophy CHILDRENFIC 3 |
| West With The Night North Point Press ADULTNF 3 |
| The Good Book Bard ADULTREF 4 |
| Preaching To Head And Heart Abingdon Press ADULTREF 4 |
| The Cost Of Discipleship Touchstone ADULTREF 3 |
| The Shipping News Simon Schuster ADULTFIC 4 |
+--------------------------------------------------------------------------------------------------------------------------------------------------------+
以下是以GROUP BY子句及其结果为特色的查询：
select publisher, category_name, avg(rating)
from bookshelf
group by category_name, publisher;
PUBLISHER CATEGORY_NAME AVG(RATING)
-------------------- -------------------- -----------
Arcade Pub CHILDRENNF 3
Simon Schuster ADULTNF 4
Mariner ADULTFIC 3
Harper Trophy CHILDRENFIC 3
Harper Festival CHILDRENPIC 1
Viking ADULTREF 2
Mariner ADULTNF 4
Houghton Mifflin CHILDRENPIC 1
Scholastic CHILDRENFIC 2.5
Abingdon Press ADULTREF 4
Princeton Univ Pr ADULTREF 3
Random House ADULTNF 4
North Point Press ADULTNF 3
W.W. Norton ADULTNF 5
Vintage Books ADULTNF 4
Grammercy CHILDRENFIC 3
Penguin ADULTREF 3
Picador ADULTFIC 4
Ballantine ADULTFIC 3
Touchstone ADULTREF 3
Harper Collins ADULTFIC 5
Little Simon CHILDRENPIC 1
Scribner ADULTNF 4
Bryla Press ADULTNF 5
St Martin'S Press ADULTFIC 3
Harper Collins CHILDRENFIC 3
Bard ADULTREF 4
Simon Schuster ADULTFIC 4
以下是相同的查询，但切换了GROUP BY子句中列的列的顺序：
select publisher, category_name, avg(rating)
from bookshelf
group by publisher, category_name;
PUBLISHER CATEGORY_NAME AVG(RATING)
-------------------- -------------------- -----------
Simon Schuster ADULTNF 4
Harper Trophy CHILDRENFIC 3
Bard ADULTREF 4
Harper Festival CHILDRENPIC 1
North Point Press ADULTNF 3
Princeton Univ Pr ADULTREF 3
Scribner ADULTNF 4
Bryla Press ADULTNF 5
Abingdon Press ADULTREF 4
Simon Schuster ADULTFIC 4
Grammercy CHILDRENFIC 3
Random House ADULTNF 4
Picador ADULTFIC 4
Harper Collins ADULTFIC 5
W.W. Norton ADULTNF 5
Vintage Books ADULTNF 4
Little Simon CHILDRENPIC 1
Harper Collins CHILDRENFIC 3
Houghton Mifflin CHILDRENPIC 1
Arcade Pub CHILDRENNF 3
Mariner ADULTNF 4
St Martin'S Press ADULTFIC 3
Scholastic CHILDRENFIC 2.5
Mariner ADULTFIC 3
Ballantine ADULTFIC 3
Penguin ADULTREF 3
Touchstone ADULTREF 3
Viking ADULTREF 2
除了以不同顺序呈现结果外，结果是相同的。在这种情况下，情况总是这样吗？
答案 0 :(得分：1)
GROUP BY中的列名称顺序无关紧要，结果将相同注意：结果是按行排序的UN，这意味着每次执行查询时 - 数据库都可能以不同的顺序返回
ORDER BY，ORDER BY中的列顺序会对行的顺序产生影响，但与实际结果集不同