Excel VLOOKUP找不到正确的行

Question

I have the following table of two columns:

102-6956821-1091413 1
115-8766130-0234619 2
109-8688911-2954602 3
109-7731824-8641056 4

If I put in the following VLOOKUP:

=+VLOOKUP(B2,B$2:C$5,2)

I get the result of:

1
2
1
1

If I change it to =+VLOOKUP(B2,B$2:C$5,2, FALSE) I get the expected:

1
2
3
4

But why is this? There is an exact match available so why does it need to approximate? If it is, why is it generating the numbers it is? How is it reducing that text value to a number that it is approximating from? Thanks!

Answer 1

Transfer from comment for the sake of an answer:

If your search list (ColumnB) were sorted you would see the results you expect anyway (though in a different order). For speed, VLOOKUP is using a binary search method for which an ordered list is necessary if to achieve meaningful results. There are exact matches only in the first half of the unsorted list (hence 1 and 2 are correct but neither 1 nor 1 is).