Count rows for which certain columns differ

[crater2150]

I have a table, where two columns contain similar data. I want to count the number of rows, where these are identical.

I found a solution, but it requires adding an extra row: suppose the two columns to compare are A and B, I add another column C with =(A1 = B1) and so on and can then use =COUNTIF(C1:Cn, "TRUE").
Is it possible to count rows with identical columns without adding such an extra column? I tried using COUNTIFS, but I can’t seem to get the syntax right.

[mikekaganski]

heh… interesting consistency to ask “count rows for which certain columns differ” in title, and then ask how to count those that don’t differ in the body

[crater2150]

oops. I actually need both, so i got it mixed up during writing. I actually checked if my example matched the rest of the text, but forgot the title^^

[mikekaganski]

=SUMPRODUCT(A1:An=B1:Bn)