Question

I want to know which one structure is good to store about 50 data in same time into MySQL?

First

 data_id  user_id      data_key    data_content
 ---------------------------------------------------
 1        2            data_key1   content 1
 2        2            data_key2   content 2
 3        2            data_key3   content 3
 ..       ..           ..          ..
 ..       ..           ..          ..
 50       2            data_key50  content 50

Seconds

 data_id  user_id  data_key1  data_key2  data_key3  .. ..  data_key50
 -------------------------------------------------------------------
 1        2        content 1  content 2  content 3  .. ..  content 50

Or have other solution? user_id will have more than 5000 users.

Answer 1

Do you know the data keys before hand and are they likely to change? If they’re along the lines of “first_name, last_name, hair_color, eye_color, birthday, …” then the second model would be feasible since you’ll often want to retrieve all of these for a user at the same time.

The first model is like having a persistent hashtable, so you’d have to store all the values as strings, and your app will have to know which keys to query for. This can make sense if the keys are user defined, however.