问题
I am trying to select of the duplicate rows in mysql table it's working fine for me but the problem is that it is not letting me select all the fields in that query , just letting me select the field name i used as distinct , lemme write the query for better understading
mysql_query("SELECT DISTINCT ticket_id FROM temp_tickets ORDER BY ticket_id")
mysql_query("SELECT * , DISTINCT ticket_id FROM temp_tickets ORDER BY ticket_id")
1st one is working fine
now when i am trying to select all fields i am ending up with errors
i am trying to select the latest of the duplicates let say ticket_id 127 is 3 times on row id 7,8,9 so i want to select it once with the latest entry that would be 9 in this case and this applies on all the rest of the ticket_id's
Any idea thanks
回答1:
Are you looking for "SELECT * FROM temp_tickets GROUP BY ticket_id ORDER BY ticket_id ?
UPDATE
SELECT t.*
FROM
(SELECT ticket_id, MAX(id) as id FROM temp_tickets GROUP BY ticket_id) a
INNER JOIN temp_tickets t ON (t.id = a.id)
回答2:
DISTINCT is not a function that applies only to some columns. It's a query modifier that applies to all columns in the select-list.
That is, DISTINCT reduces rows only if all columns are identical to the columns of another row.
DISTINCT must follow immediately after SELECT (along with other query modifiers, like SQL_CALC_FOUND_ROWS). Then following the query modifiers, you can list columns.
RIGHT:
SELECT DISTINCT foo, ticket_id FROM table...Output a row for each distinct pairing of values across ticket_id and foo.
WRONG:
SELECT foo, DISTINCT ticket_id FROM table...If there are three distinct values of ticket_id, would this return only three rows? What if there are six distinct values of foo? Which three values of the six possible values of foo should be output?
It's ambiguous as written.
回答3:
You can use group by instead of distinct. Because when you use distinct, you'll get struggle to select all values from table. Unlike when you use group by, you can get distinct values and also all fields in table.
回答4:
You can use like that
mysql_query("SELECT DISTINCT(ticket_id), column1, column2, column3 FROM temp_tickets ORDER BY ticket_id")
回答5:
use a subselect:
http://forums.asp.net/t/1470093.aspx
来源：https://stackoverflow.com/questions/7250566/mysql-select-distinct