没有选择最大值

Question

I am using the query

select max(entry_no) from tbl_Invmaster

but its giving me ans 9 however the max value is 10.

Answer 1

You probably have the numbers in a VARCHAR column. Ordering in those fields is by alphabetcal order . That way 9 is bigger than 10 . Explanation from the link:

To determine which of two strings comes first in alphabetical order, their first letters are compared. If they differ, then the string whose first letter comes earlier in the alphabet is the one which comes first in alphabetical order. If the first letters are the same, then the second letters are compared, and so on. If a position is reached where one string has no more letters to compare while the other does, then the first (shorter) string is deemed to come first in alphabetical order.

Your best solution is not to store numbers in VARCHAR columns but instead use the appropriate type, eg INT . That way your query would return the correct result.

If that is not an option for you, you could CAST the column to an integer type. Eg in SQL Server you would write:

select max(CAST(entry_no AS INT)) from tbl_Invmaster

Answer 2

select max( to_number( entry_no )) from tbl_invmaster