Question

In cases when some one needs to store more than one value in a in a cell, what approach is more desirable and advisable, storing it with delimiters or glue and exploding it into an array later for processing in the server side language of choice, for example.

$returnedFromDB = “159|160|161|162|163|164|165”;
$myIdArray = explode(“|”,$returnedFromDB);

or as a JSON or PHP serialized array, like this.

:6:{i:0;i:1;i:1;i:2;i:2;i:3;i:3;i:4;i:4;i:5;i:5;i:6;}

then later unserialize it into an array and work with it,

OR

have a new row for every new entry like this

postid 12 | showto 2
postid 12 | showto 3
postid 12 | showto 5
postid 12 | showto 6
postid 12 | showto 8

instead of postid 12 | showto “2|3|4|6|8|5|”.
OR postid 12 | showto “:6:{i:0;i:2;i:1;i:3;i:2;i:3;i:3;i:4;i:4;i:5;i:5;i:6;}”.

Thanks, looking forward to your opinions 😀

Answer 1

In cases when some one needs to store more than one value in a in a cell, what approach is more desirable and advisable, storing it with delimiters or glue and exploding it into an array later for processing in the server side language of choice, for example.

Neither. Oh goodness, neither! Edgar F. Codd is rolling in his grave right now.

Storing delimited data in a text field is no better than storing it in a flat file. The data becomes unqueryable. Storing PHP serialized data in a text field is even worse because then only PHP can parse the data.

You want a nice, happy, normalized database.

The thing you’re trying to describe is a many-to-many relationship. Each user can maintain one or more posts. Likewise, each post can be maintained by one or more user. Right? Then something like this will work.

CREATE TABLE users (
    user_id INTEGER PRIMARY KEY,
    ...
);

CREATE TABLE posts (
    post_id INTEGER PRIMARY KEY,
    ...
);
CREATE TABLE user_posts (
    user_id INTEGER REFERENCES users(user_id),
    post_id INTEGER REFERENCES posts(post_id),
    UNIQUE KEY(user_id, post_id)
);

-- All posts made by user 22.
SELECT posts.*
  FROM posts, user_posts
 WHERE user_posts.user_id = 22
   AND posts.post_id = user_posts.post_id

-- All users that worked on post 47
SELECT users.*
  FROM users, user_posts
 WHERE user_posts.post_id = 47
   AND users.user_id = user_posts.user_id