Question

I have table called Buttons. Buttons table i have column button_number . Table contain more than 100 records. Now i have to select a buttons number between 10 to 50. When i used this following query it’s not returning zero row.

select * from Buttons where button_number >= '10' and button_number <='50'

What’s the problem in the query. If i use the same query with different column(data type is int) then it’s working fine. Is the problem because of the data type of the column? If so what’s the fix for this?

Note : button_number column data type is Varchar.

Answer 1

The button_number is varchar and you are trying to do an integer style comparison. You will need to cast the button_number column to an integer.

select * from Buttons where 
    convert(integer, button_number) >= 10 and convert(integer, button_number) <= 50

Edit

The above query will require a table scan since it needs to convert every button_number to an integer before applying the where clause. This isn’t a problem for 100 rows, but would be an issues for large numbers.

As mentioned in Mikael Eriksson’s answer, a better alternative would be to change the type of button_number to an integer type (if possible). This would have several advantages:

• There would be no chance of entering a non-integer value in the column
• You would then be able to apply an integer index to the column. This would greatly improve the speed of your query when the table contains large numbers of rows.