November 21, 2012 at 10:29 pm
Hi All,
We are getting different results for MAX function with nvarchar and varchar columns.
create table my_table(id1 nvarchar(10), id2 varchar(10);
insert into my_table('-1','-1);
insert into my_table('1','1);
select max(id1) from my_table; -> -1
but
select max(id2) from my_table; -> 1
is it the default behavior? Any way to change this?
Regards
November 21, 2012 at 10:41 pm
Change the COLLATE for one of the columns.
Try this:
create table my_table(id1 nvarchar(10), id2 varchar(10))
SELECT TABLE_NAME, COLUMN_NAME,CHARACTER_SET_NAME, COLLATION_NAME
FROM information_schema.columns
WHERE TABLE_NAME = 'my_table'
insert into my_table VALUES ('-1','-1');
insert into my_table VALUES ('1','1');
SELECT MAX(id1 COLLATE Latin1_General_Bin2), MAX(id2)
FROM my_table
DROP table my_table
You can see from the first SELECT that these columns have the same COLLATE sequence but different character sets. Changing to a binary collation resolves the issue you inquired about. Be warned that it may also cause other undesired side effects (test, test, test!).
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November 26, 2012 at 3:09 am
Thanks very much for you answer.
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