how to do subtraction in mysql

Question

i want to subtract 1 from a variable who is stored in my table in mysql

i do it by this query

UPDATE table SET  var = var -1

but when i do it

0 - 1 = -1

but mysql do

0 - 1 = 9223372036854775807 when i set in bigint when i set it to int property then he do

0 -1 = 2147483647

what i do to get

0 - 1 = -1

Is the data type signed or unsigned? And was the value 0 before? — My Other Me, May 11 '10 at 05:31
@Richa: Why again? You have already got the answer here http://stackoverflow.com/questions/2807769/minus-value-in-mysql-table-not-worked — Amsakanna, May 11 '10 at 05:34
@Veer: yeah he already got answers there, i suggested he use BIGINT. then he deleted his question. now he is asking for BIGINT scenario, but i refuse to answer now, I don't know anything bigger than BIGINT (at least with whole number type) — Michael Buen, May 11 '10 at 05:44

score 1 · Accepted Answer · edited May 23 '17 at 12:19

1

You need to choose a different (signed) data type that allows storing negative values.

look here for some background :

edited May 23 '17 at 12:19

Community

answered May 11 '10 at 05:41

lexu

1 Answers1