Question

I am asked to fix a php function in my work. The prototype is:

function select($cols, $table, $cond, $order, $start, $max);

It queries the database with odbc_exec() and returns the number of rows with odbc_num_rows(). Function code is like this:

$this->query = "SELECT $cols FROM $table ";
if($cond) $this->query .= "WHERE $cond";
if($order) $this->query .= " ORDER BY ".$order;

This function is used in many places so i can’t write it from scratch. It gets records from many tables. Until yesterday it was not using $max variable so it was reading all the records from the database. They are using iSeries Access ODBC Driver. I looked at here for answer but couldn’t found.

I want to use the $start variable, to start reading from $start and read $max rows. If $start is 100 and $max 50, i want to get the records between 100-150. I added this part yesterday:

if($max) $this->query .= " FETCH FIRST " . $max . " ROWS ONLY ";

I couldn’t found anything useful for my problem. I know i can do it for one table using id or something like that. But i am looking for a general solution.

Answer 1

I solved the problem.

First, you need the convert each column name in $cols to $table.columnName with php.

$this->query .= " ( SELECT ROW_NUMBER() OVER() AS rownum, $convertedColumns
                       FROM $table ) AS tmp WHERE rownum > ". $start ." " ;
if($max) {
    $last = $start + $max;
    $this->query .= " AND rownum <= ". $last . " ";
}

And as result query looks like this:

SELECT $cols FROM 
    ( SELECT ROW_NUMBER() OVER() AS rownum, $convertedCols ) AS tmp
WHERE rownum > $start AND rownum <= $max