How implement one-to-many objects database in sqlite for android

Question

I\'m quite new to SQLite and SQL and I am struggling with how to approach the following:

My app will display a list of community members. I

Answer 1

You need to have two tables:

1.Users

USER_ID | NAME

2.TWEETS

USER_ID | TIME | MESSAGE

Now for the explanation:

Table 1 is represents the users, there is all the data about the user, like name, phone, address etc.

Table 2 is for all the tweets of all the users, and there is a column that connects between user and his tweet. In table 2 USER_ID is foreign key, that points to exactly one row in the users table.

To get all the tweets for one user, you can write the next query:

Select TWEETS.MESSAGE, TWEETS.TIME
from Users, TWEETS
where Users.USER_ID = TWEETS.USER_ID
and Users.NAME = "Pierre";

Answer 2

This is a typical "JOIN" scenario where you have a one-to-many relationship between Users and Posts.

Here is an example of a query that would display all users and their posts:

SELECT u.User_ID, u.Name, p.Time, p.Message
FROM Users u INNER JOIN Posts p ON u.User_ID = p.User_ID

This will produce a resultset with four columns. Each "Tweet" will be displayed with its related User record. The 'u.' and 'p.' syntax are table aliases used to make the query easier to read.

Answer 3

An answer has been given and accepted already, but I wanted to add this.

What you want is one table with users, users. In this table you store your user information (user_id, name).

In your Tweets table, store all tweets for all users. One tweet per row. I'm using tweet_id as PRIMARY KEY for the Tweets table.

You can then 'link' the two in code by doing a JOIN like Dave Swersky said.

For example:

Users
--------------------------
user_id   |   user_name
--------------------------
   123    |    'Terry'
   34     |    'Pierre'

Tweets
-----------------------------------------------------------------------
tweet_id |   user_id   |  time      |         message     
-----------------------------------------------------------------------
   0     |    123      | 135646     |  'This is a tweet'
   1     |    123      | 132646     |  'This is another tweet by Terry'
   2     |    34       | 352646     |  'Pierre\'s tweet'

I'm not sure what name is for in your Tweets table. As far as I know tweets do not have a name/subject(?). You do not need to store the user name in both the tweets and users table.

For a quick SQLFiddle, go here: http://www.sqlfiddle.com/#!2/43492/1/0

Join

SELECT u.user_id, u.name, t.time, t.message, t.time 
FROM my_users u
INNER JOIN tweets t ON u.user_id = t.user_id