"simple" calculations using database values

[xwishmasterx]

I was wondering how to write something like this:

 

if (table1.column1 + table2.column2 > table3.column3  then .....

 

I am confused where to put ( ) and '

 

 

[3raser]

Something like this?

 

$total = table_col1 + table_col2 + table_col3;

echo $total;

 

EDIT:

 

if(table_col1 + table_col2 + table_col3 == 20)
{
echo "adds up to 20 exactly";
}
else
{
echo "does not equal";
}