在Mysql数据库的单个字段中存储数组的替代方法

Question

How to avoid storing array of users in one field? I have a session table that have a field with users ids that joins the session(joinusers_id). How I should approach on inserting them? The easy way is to put them separated with comma, but I guess it isn't the most efficient way. Attached is a screenshot of my current implementation of session Table:

Answer 1

Ok, we are talking about databases and normalization.

http://en.wikipedia.org/wiki/Database_normalization

No, please do not use non-atomic fields, it is bad and you will get in to trouble, if you want to join such non-atomic fields.

I would suggest you are doing this:

You have users, so please create a user table containing all the things belonging to a user. The user table needs a primary key: user_mailaddress

You have sessions, create a session table ... primary key: session_id

Now create a table user_session , this table has two attributes (columns) user_mailaddress and session_id using this table you can connect the two tables together.

SELECT *
FROM user
NATURAL_JOIN user_session
NATURAL_JOIN session

The natural join will join the tables, where the attributes and the contents of the attributes are comparable.

NOTE: The tables user and session are called entities. The table user_session is called the relation. So this is called the entity-relationship model. => http://en.wikipedia.org/wiki/Entity%E2%80%93relationship_model

To read it in more depth: https://www.stat.auckland.ac.nz/~paul/ItDT/HTML/node42.html