Nested or Joins query for MySQL using PHP

I have many a times tried using nested query for MySQL in PHP, but it does not work. Is it not possible to do nested/Joins queries?

Just a Scenario:

I have two tables one table with user id and the other with data. User logins and with sessions I have to cross check two different tables with 开发者_StackOverflow社区user id (user and data). Is it not possible to nest/join these two tables to write a single query statement.

In short is nesting or joining two or more tables permitted in PHP coding?

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YES, it is possible to join two or more tables in MySQL (and therefore, also when using PHP).

You need to post your table schema, if you want us to show a relevant join query. You could, however, try something like:

SELECT * FROM user AS t1
CROSS JOIN data AS t2
    ON t1.userid=t2.userid
WHERE t1.userid='154'

(This query presumes that there always will be one row with the userid in both tables. You should use LEFT JOIN instead of CROSS JOIN to return a row even if there is no row in data for the userid. 154 is just an example userid.)

Have a look at http://dev.mysql.com/doc/refman/5.5/en/join.html for information on the JOIN syntax.

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users 

| user_id | username | password | enabled |
|---------|----------|----------|---------|
|    1    | john     | sgsd2gg  |   1     |
|    2    | jane     | sdshdhd  |   0     |

users_data

|udata_id| user_id | some_column       | 
|--------|---------|-------------------|
|   1    |   1     | Some title        |
|   2    |   2     | another title     |

Since you haven't posted your table schema, I can't give you an exact solution. But supposing you have a users table and a users_data table, where users_data are owned by a user. You can do a join on the table to retrieve all the data.

SELECT * -- Don't select all fields unless you need it
FROM users U LEFT JOIN users_data UD ON U.user_id = UD.user_id
WHERE U.user_id = 1

This would pull all the records for user with an ID of 1. This is a very simplistic join, but it should give you an idea.

Here's an example that visually describes the different options you can use : SQL Join Differences