Question

Consider the following “users” table:

uid  followers  following  ff_fraction
--------------------------------------
1    40         2          20
2    10         3           3
3     0         2           0
4     5         0           5
5    77         2
6     9         3

I want to calculate, for each user, the fraction of followers/following, rounded to a whole number. I filled in the table for the first 4 users:

1. 40/2 = 20
2. 10/3 = 3.3333 => rounded 3
3. 0/2 = 0
4. 5/0 => this would give an error, so I counted +1, making 5/1 = 5

I now have the following query, but it does not account for “following” being zero (and that it thus would have to add 1 in order to not get a devision by zero error):

UPDATE users SET ff_fraction = ROUND(followers/following)

Is it possible to solve this in a MySQL query?

Answer 1

You can do the following:

UPDATE users SET ff_fraction = ROUND(followers/if(following>0,following,1))