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suppose i have a table with name "Transport"

in this table i have 3 fields : a,b,c

how i can subtract a-b and put in c field

Note :
1- unfortunately , all fields have text type .
2- now , this table have about 5000 record and i cant change field type or anything else , and i want only update field c with subtract of a-b

thanks guys
[no name] 7-Oct-14 15:10pm    
String - string = ? What is it that you think you are subtracting?

1 solution

It's bad idea to store numbers as a text.

You have to use query similar to:
UPDATE Transport SET c = CLng(a)-CLng(b)

As you can see, i use CLng function to convert text to long integer.
Note: Conversion may failed when text stored in that field cannot be explicitly converted.

For further information, please see:
CLng function[^]
UPDATE statement[^]
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