Mysql Arithmetic..

[section31]

Hello fellas...I need some clarification on something.

 

Ok...i'm not clear on mysql float datatypes. I mean, my script is working but I would like to know exactly what its doing.

 

I'm running a particular query...

>$sql = "UPDATE table SET votes=votes+1, votecount=votecount+$rating, rating=votecount/votes WHERE linkid=$id";

mysql datatypes are as follows

votes (int)

votecount (int)

rating (float)

 

the part i'm unclear about is the division i used here "rating=votecount/votes"

I read up a little at mysql.com and it discusses some arithmitic operations, but not division... so i'm dividing 2 integers and I want to know what type of division mysql does (percision wise).

 

This is what i'm getting pushed into the database..Ex. (29/6) = 4.83333

 

You would think since its a repeating decimal, it would push the maximum length of numbers, but that isn't the case.

[kaseytraeger]

Hi section31,

 

I haven't done a lot of MySQL programming, but I've been programming object oriented languages such as C++ and Java for several years. In those languages, when I came upon a dilemma such as this, I would simply cast the resultant value into whatever data type form I wanted.

 

For instance, consider the following line of code:

>int x;
int y =10;
int z = 3;

// If left uncast, the following line would give some sort of error because y/z is not an integer. The actual value is a never-ending decimal 3.333......
x = y/z;

// However, if I cast the result as an integer (to match the data type of "x"), the line will execute smoothly, and give the result of x=3
x = (int)y/z;  // Casts 10/3 as an integer before assigning the value to variable x.

 

I don't know if casting is an option in MySQL, but it was worth a mention!

 

Good luck!

[section31]

nah..i don't think casting is an option.

 

thanks anyway,

dave

[btrfld]

If you're concerned about the decimal, you can use the MySQL ROUND(). Check out the Mathematical functions.

[section31]

If you're concerned about the decimal, you can use the MySQL ROUND(). Check out the Mathematical functions.

No i wanted a decimal...just unsure why it rounds to the 6th decimal place...

 

Oh...another quick question if anyone can help..anyone know which is faster...mysql LOCATE function or LIKE.