Updating specific table values?

1

i’m very new to php+mysql, and i’m trying to figure out how to update values. so far, every tutorial i’ve seen online targets which values to update using the “where” statement, but isn’t this kind of slow compared to just targeted specific values via their order in the table?

basically, if this were c++ or actionscript, and the table were an array, i’d just want to modify the value via it’s reference, rather then searching a parallel array for values, like this


column[reference_number]= new_value;

rather than


for(i=0;i=table_length;i++)
{
     if(column1*==reference_number)
     {
          column2*=new_value;
     }
}

so uhm, is this possible, or can i only acheive this if a populate another column with values corresponding to the row number, and do a WHERE search for the appropriate number in that column (which seems inefficient as hell)? TIA^^