问题
I'm reading through some old code at work, and have noticed that there are several views with an order by 1 clause. What does this accomplish?
Example:
Create view v_payment_summary AS
SELECT A.PAYMENT_DATE,
(SELECT SUM(paymentamount)
FROM payment B
WHERE PAYMENT_DATE = B.PAYMENT_DATE
and SOME CONDITION) AS SUM_X,
(SELECT SUM(paymentamount)
FROM payment B
WHERE PAYMENT_DATE = B.PAYMENT_DATE
and SOME OTHER CONDITION) AS SUM_Y
FROM payment A
ORDER BY 1;
回答1:
This:
ORDER BY 1
...is known as an "Ordinal" - the number stands for the column based on the number of columns defined in the SELECT clause. In the query you provided, it means:
ORDER BY A.PAYMENT_DATE
It's not a recommended practice, because:
- It's not obvious/explicit
- If the column order changes, the query is still valid so you risk ordering by something you didn't intend
回答2:
This is useful when you use set based operators e.g. union
select cola
from tablea
union
select colb
from tableb
order by 1;
回答3:
I believe in Oracle it means order by column #1
回答4:
This will sort your results by the first column returned. In the example it will sort by payment_date.
回答5:
it simply means sorting the view or table by 1st column of query's result.
回答6:
As mentioned in other answers ORDER BY 1 orders by the first column.
I came across another example of where you might use it though. We have certain queries which need to be ordered select the same column. You would get a SQL error if ordering by Name in the below.
SELECT Name, Name FROM Segment ORDER BY 1
回答7:
Also see:
http://www.techonthenet.com/sql/order_by.php
For a description of order by. I learned something! :)
I've also used this in the past when I wanted to add an indeterminate number of filters to a sql statement. Sloppy I know, but it worked. :P
回答8:
An example here from a sample test WAMP server database:-
mysql> select * from user_privileges;
| GRANTEE | TABLE_CATALOG | PRIVILEGE_TYPE | IS_GRANTABLE |
+--------------------+---------------+-------------------------+--------------+
| 'root'@'localhost' | def | SELECT | YES |
| 'root'@'localhost' | def | INSERT | YES |
| 'root'@'localhost' | def | UPDATE | YES |
| 'root'@'localhost' | def | DELETE | YES |
| 'root'@'localhost' | def | CREATE | YES |
| 'root'@'localhost' | def | DROP | YES |
| 'root'@'localhost' | def | RELOAD | YES |
| 'root'@'localhost' | def | SHUTDOWN | YES |
| 'root'@'localhost' | def | PROCESS | YES |
| 'root'@'localhost' | def | FILE | YES |
| 'root'@'localhost' | def | REFERENCES | YES |
| 'root'@'localhost' | def | INDEX | YES |
| 'root'@'localhost' | def | ALTER | YES |
| 'root'@'localhost' | def | SHOW DATABASES | YES |
| 'root'@'localhost' | def | SUPER | YES |
| 'root'@'localhost' | def | CREATE TEMPORARY TABLES | YES |
| 'root'@'localhost' | def | LOCK TABLES | YES |
| 'root'@'localhost' | def | EXECUTE | YES |
| 'root'@'localhost' | def | REPLICATION SLAVE | YES |
| 'root'@'localhost' | def | REPLICATION CLIENT | YES |
| 'root'@'localhost' | def | CREATE VIEW | YES |
| 'root'@'localhost' | def | SHOW VIEW | YES |
| 'root'@'localhost' | def | CREATE ROUTINE | YES |
| 'root'@'localhost' | def | ALTER ROUTINE | YES |
| 'root'@'localhost' | def | CREATE USER | YES |
| 'root'@'localhost' | def | EVENT | YES |
| 'root'@'localhost' | def | TRIGGER | YES |
| 'root'@'localhost' | def | CREATE TABLESPACE | YES |
| 'root'@'127.0.0.1' | def | SELECT | YES |
| 'root'@'127.0.0.1' | def | INSERT | YES |
| 'root'@'127.0.0.1' | def | UPDATE | YES |
| 'root'@'127.0.0.1' | def | DELETE | YES |
| 'root'@'127.0.0.1' | def | CREATE | YES |
| 'root'@'127.0.0.1' | def | DROP | YES |
| 'root'@'127.0.0.1' | def | RELOAD | YES |
| 'root'@'127.0.0.1' | def | SHUTDOWN | YES |
| 'root'@'127.0.0.1' | def | PROCESS | YES |
| 'root'@'127.0.0.1' | def | FILE | YES |
| 'root'@'127.0.0.1' | def | REFERENCES | YES |
| 'root'@'127.0.0.1' | def | INDEX | YES |
| 'root'@'127.0.0.1' | def | ALTER | YES |
| 'root'@'127.0.0.1' | def | SHOW DATABASES | YES |
| 'root'@'127.0.0.1' | def | SUPER | YES |
| 'root'@'127.0.0.1' | def | CREATE TEMPORARY TABLES | YES |
| 'root'@'127.0.0.1' | def | LOCK TABLES | YES |
| 'root'@'127.0.0.1' | def | EXECUTE | YES |
| 'root'@'127.0.0.1' | def | REPLICATION SLAVE | YES |
| 'root'@'127.0.0.1' | def | REPLICATION CLIENT | YES |
| 'root'@'127.0.0.1' | def | CREATE VIEW | YES |
| 'root'@'127.0.0.1' | def | SHOW VIEW | YES |
| 'root'@'127.0.0.1' | def | CREATE ROUTINE | YES |
| 'root'@'127.0.0.1' | def | ALTER ROUTINE | YES |
| 'root'@'127.0.0.1' | def | CREATE USER | YES |
| 'root'@'127.0.0.1' | def | EVENT | YES |
| 'root'@'127.0.0.1' | def | TRIGGER | YES |
| 'root'@'127.0.0.1' | def | CREATE TABLESPACE | YES |
| 'root'@'::1' | def | SELECT | YES |
| 'root'@'::1' | def | INSERT | YES |
| 'root'@'::1' | def | UPDATE | YES |
| 'root'@'::1' | def | DELETE | YES |
| 'root'@'::1' | def | CREATE | YES |
| 'root'@'::1' | def | DROP | YES |
| 'root'@'::1' | def | RELOAD | YES |
| 'root'@'::1' | def | SHUTDOWN | YES |
| 'root'@'::1' | def | PROCESS | YES |
| 'root'@'::1' | def | FILE | YES |
| 'root'@'::1' | def | REFERENCES | YES |
| 'root'@'::1' | def | INDEX | YES |
| 'root'@'::1' | def | ALTER | YES |
| 'root'@'::1' | def | SHOW DATABASES | YES |
| 'root'@'::1' | def | SUPER | YES |
| 'root'@'::1' | def | CREATE TEMPORARY TABLES | YES |
| 'root'@'::1' | def | LOCK TABLES | YES |
| 'root'@'::1' | def | EXECUTE | YES |
| 'root'@'::1' | def | REPLICATION SLAVE | YES |
| 'root'@'::1' | def | REPLICATION CLIENT | YES |
| 'root'@'::1' | def | CREATE VIEW | YES |
| 'root'@'::1' | def | SHOW VIEW | YES |
| 'root'@'::1' | def | CREATE ROUTINE | YES |
| 'root'@'::1' | def | ALTER ROUTINE | YES |
| 'root'@'::1' | def | CREATE USER | YES |
| 'root'@'::1' | def | EVENT | YES |
| 'root'@'::1' | def | TRIGGER | YES |
| 'root'@'::1' | def | CREATE TABLESPACE | YES |
| ''@'localhost' | def | USAGE | NO |
+--------------------+---------------+-------------------------+--------------+
85 rows in set (0.00 sec)
And when it is given additional order by PRIVILEGE_TYPE or can be given order by 3 . Notice the 3rd column (PRIVILEGE_TYPE) getting sorted alphabetically.
mysql> select * from user_privileges order by PRIVILEGE_TYPE;
+--------------------+---------------+-------------------------+--------------+
| GRANTEE | TABLE_CATALOG | PRIVILEGE_TYPE | IS_GRANTABLE |
+--------------------+---------------+-------------------------+--------------+
| 'root'@'127.0.0.1' | def | ALTER | YES |
| 'root'@'::1' | def | ALTER | YES |
| 'root'@'localhost' | def | ALTER | YES |
| 'root'@'::1' | def | ALTER ROUTINE | YES |
| 'root'@'localhost' | def | ALTER ROUTINE | YES |
| 'root'@'127.0.0.1' | def | ALTER ROUTINE | YES |
| 'root'@'127.0.0.1' | def | CREATE | YES |
| 'root'@'::1' | def | CREATE | YES |
| 'root'@'localhost' | def | CREATE | YES |
| 'root'@'::1' | def | CREATE ROUTINE | YES |
| 'root'@'localhost' | def | CREATE ROUTINE | YES |
| 'root'@'127.0.0.1' | def | CREATE ROUTINE | YES |
| 'root'@'::1' | def | CREATE TABLESPACE | YES |
| 'root'@'localhost' | def | CREATE TABLESPACE | YES |
| 'root'@'127.0.0.1' | def | CREATE TABLESPACE | YES |
| 'root'@'::1' | def | CREATE TEMPORARY TABLES | YES |
| 'root'@'localhost' | def | CREATE TEMPORARY TABLES | YES |
| 'root'@'127.0.0.1' | def | CREATE TEMPORARY TABLES | YES |
| 'root'@'localhost' | def | CREATE USER | YES |
| 'root'@'127.0.0.1' | def | CREATE USER | YES |
| 'root'@'::1' | def | CREATE USER | YES |
| 'root'@'localhost' | def | CREATE VIEW | YES |
| 'root'@'127.0.0.1' | def | CREATE VIEW | YES |
| 'root'@'::1' | def | CREATE VIEW | YES |
| 'root'@'127.0.0.1' | def | DELETE | YES |
| 'root'@'::1' | def | DELETE | YES |
| 'root'@'localhost' | def | DELETE | YES |
| 'root'@'::1' | def | DROP | YES |
| 'root'@'localhost' | def | DROP | YES |
| 'root'@'127.0.0.1' | def | DROP | YES |
| 'root'@'127.0.0.1' | def | EVENT | YES |
| 'root'@'::1' | def | EVENT | YES |
| 'root'@'localhost' | def | EVENT | YES |
| 'root'@'127.0.0.1' | def | EXECUTE | YES |
| 'root'@'::1' | def | EXECUTE | YES |
| 'root'@'localhost' | def | EXECUTE | YES |
| 'root'@'127.0.0.1' | def | FILE | YES |
| 'root'@'::1' | def | FILE | YES |
| 'root'@'localhost' | def | FILE | YES |
| 'root'@'localhost' | def | INDEX | YES |
| 'root'@'127.0.0.1' | def | INDEX | YES |
| 'root'@'::1' | def | INDEX | YES |
| 'root'@'::1' | def | INSERT | YES |
| 'root'@'localhost' | def | INSERT | YES |
| 'root'@'127.0.0.1' | def | INSERT | YES |
| 'root'@'127.0.0.1' | def | LOCK TABLES | YES |
| 'root'@'::1' | def | LOCK TABLES | YES |
| 'root'@'localhost' | def | LOCK TABLES | YES |
| 'root'@'127.0.0.1' | def | PROCESS | YES |
| 'root'@'::1' | def | PROCESS | YES |
| 'root'@'localhost' | def | PROCESS | YES |
| 'root'@'::1' | def | REFERENCES | YES |
| 'root'@'localhost' | def | REFERENCES | YES |
| 'root'@'127.0.0.1' | def | REFERENCES | YES |
| 'root'@'::1' | def | RELOAD | YES |
| 'root'@'localhost' | def | RELOAD | YES |
| 'root'@'127.0.0.1' | def | RELOAD | YES |
| 'root'@'::1' | def | REPLICATION CLIENT | YES |
| 'root'@'localhost' | def | REPLICATION CLIENT | YES |
| 'root'@'127.0.0.1' | def | REPLICATION CLIENT | YES |
| 'root'@'::1' | def | REPLICATION SLAVE | YES |
| 'root'@'localhost' | def | REPLICATION SLAVE | YES |
| 'root'@'127.0.0.1' | def | REPLICATION SLAVE | YES |
| 'root'@'127.0.0.1' | def | SELECT | YES |
| 'root'@'::1' | def | SELECT | YES |
| 'root'@'localhost' | def | SELECT | YES |
| 'root'@'127.0.0.1' | def | SHOW DATABASES | YES |
| 'root'@'::1' | def | SHOW DATABASES | YES |
| 'root'@'localhost' | def | SHOW DATABASES | YES |
| 'root'@'127.0.0.1' | def | SHOW VIEW | YES |
| 'root'@'::1' | def | SHOW VIEW | YES |
| 'root'@'localhost' | def | SHOW VIEW | YES |
| 'root'@'localhost' | def | SHUTDOWN | YES |
| 'root'@'127.0.0.1' | def | SHUTDOWN | YES |
| 'root'@'::1' | def | SHUTDOWN | YES |
| 'root'@'::1' | def | SUPER | YES |
| 'root'@'localhost' | def | SUPER | YES |
| 'root'@'127.0.0.1' | def | SUPER | YES |
| 'root'@'127.0.0.1' | def | TRIGGER | YES |
| 'root'@'::1' | def | TRIGGER | YES |
| 'root'@'localhost' | def | TRIGGER | YES |
| 'root'@'::1' | def | UPDATE | YES |
| 'root'@'localhost' | def | UPDATE | YES |
| 'root'@'127.0.0.1' | def | UPDATE | YES |
| ''@'localhost' | def | USAGE | NO | +--------------------+---------------+-------------------------+--------------+
85 rows in set (0.00 sec)
DEFINITIVELY, a long answer and alot of scrolling.
Also I struggled hard to pass the output of the queries to a text file.
Here is how to do that without using the annoying into outfile thing-
tee E:/sqllogfile.txt;
And when you are done, stop the logging-
tee off;
Hope it adds more clarity.
来源：https://stackoverflow.com/questions/3445118/what-is-the-purpose-of-order-by-1-in-sql-select-statement