Question

I need help on how to get/display some informations from DB (MySQl)

My current table looks like this:

id | title | level | start_afterID | days | 

1  |   A   |   0   |       0       |   7  |
2  |   B   |   1   |       1       |   5  |
3  |   C   |   1   |       2       |   3  |
4  |   D   |   1   |       3       |   2  |
5  |   E   |   1   |       4       |   2  |
6  |   F   |   1   |       3       |   6  |

Level ‘0’ means that this job will start first and start day and time is in other table ($config_start)

All others entry with level = 1 don’t have fixed start, just id of job (start_afterID) after which they start.

Also every job will last in number of days from DAYS field.

In this table job with ID 6 (title F) must start after jobID 3 – And that start time is something like:

$config_start + jobID 3 + jobID 2;

$end of this job is:

$config_start + jobID 3 + jobID 2 + 6;

At the end, I will need to display all jobs from DB in incoming order.

I tried my best with this, but i can’t figure how to check all parent levels and calculate it.
Also, I can create new administration for this and maybe there is a better way of inserting new jobs ?

THANKS for any help on this,

Answer 1

First of all, I advise you to rethink the level column – IIUC this is only a boolea, telling you wether this is a job root or not – this information is also prsent in start_afterID being 0.

Now calculating the start and end times is a non-trivial job, that requires lots of DB avvess, so I advise you to create a second table with id|startday|endday and move the calculation logic in a way, that this (essentially cache) table is updated on job change, leaving you with a fast query path for normal operations.

To calculate the contents of this timing table, you would do something like

function docalc($after,$startday) {

    $sql="SELECT * FROM tablename WHERE start_afterID=$after";

    //Run the query, this depends on your framework used

    //Pseudocode from here - again depends on your framework
    foreach ($row) {
        $id=$row['id'];
        $endday=$startday+$row['days']; //This will not be a simple addition, depending on your data types

        //Adapt the following to your data types
        $sql="REPLACE INTO timingcache SET id=$id, startday=$startday, endday=$endday";
        //Run the query - depends on your framework

        docalc($id,$endday);

    } //for each row

}


//this assumes $config_start is set correctly
docalc(0,$config_start);