CODEWITHSUNDEEP
mysqlmath
Alec
Alec

Reputation: 979

MySQL UPDATE Math Not Working?

I am performing a query that will subtract a balance from a row by 1. However, after the query will run successfully once, the math becomes off.

If I subtract 0.1 from 1.0, it gives me 0.9. However, the next time I subtract 0.1, I get 0.8000000000000001. Here is the query I'm using:

UPDATE ACCOUNTS SET BALANCE=BALANCE-$amt WHERE ID=$user_id

$amt is 0.1 and $user_id is 1, in this case.

Why does the math change after a successful query? Thanks!

Upvotes: 1

Views: 76

Answers (2)

Alec
Alec

Reputation: 979

Thanks to @tintran I figured out that it had to do with the LENGTH/VALUE part of being a decimal. I changed it to (10,8). 8 is because I am dealing in Bitcoin and 8 decimal places is the max I could go.

Thanks everyone!

Upvotes: 1

The Hungry Dictator
The Hungry Dictator

Reputation: 3484

UPDATE ACCOUNTS SET BALANCE=ROUND((BALANCE-$amt),2) WHERE ID=$user_id

try this....

Upvotes: 0

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