Recomment free cells on matrix . using MySQL

Question

I have two table's like

1. container

   it contains

   • refid as primarykey
   • rows // number of rows in a matrix
   • columns // number of columns in a matrix

2. data_on_matrix

   it contains

   • refid as primarykey
   • cell_id // the cell of the data placed on matrix
   • text_data // data on matrix
   • container_id // data on matrix

image here

I am just make this UI by container column X rows. If someone click on any cell that cell was filled by data by inserting one row on data_on_matrix table.

My Problem is

How to recomment free cells on the container for users. How to achive by this whether SQL or Any UI tricks available for that?

Answer 1

(repeating from comment)

If you look for cells in a matrix which are not there, you need a "numbers" table since SQL can't create something out of nothing.

create table numbers (nr int(11) not null primary key auto_increment);
insert into numbers values (1),(2),(3),(4),(5);

(and so on until you maximal ever possible or thinkable dimension).

Then you need the row number and column number of your data_on_matrix entry:

alter table data_on_matrix add column row_id int(11) not null, add column col_id int(11) not null;

If you want to read the cells of a matrix which are already there, you just read

select row_id, col_id, text_data from data_on_matrix where refid = {$refid};

If you look for free cells, just select

select r.nr as row_id, c.nr as col_id
from numbers r, numbers c
left join data_on_matrix d on d.col_id = c.id and d.row_id = r.id and d.refid = {$refId}
where d.ref_id is null and r.id <= {$rows} and c.id <= {$columns}

with refid, rows and columns coming out of table container. It would also be easy to join container directly, but probably you already have a list of containers with their properties in php.