Joining two tables together in one database

Hey guys I have a ques开发者_JAVA技巧tion which is how to get information from one tables and then with that info e.g. a name and then query the database to tell me a value in table 2.

So in short I have a friend system going but I cant get the pictures for that user because it is in another table. I can get his name but i can not get his picture. So how do you get his picture which is in table 1 and the name is in table 2.

table 1
name Users

id    username  password       Email          picture                   theme  
1      bob       dabsd2323ty     hjas@hsdf      uploads/adsda.png       themes/theme1.png
2      fred        dabsd2323ty     hjas@hsdf      uploads/adsda.png       themes/theme1.png


table 2
name Friends

id  sender    receiver  checked  
1     bob      fred       2

2 means he has checked it and accepted it.

so i can get the name from table 2 but i dont know how to get the picture for the user from table 1

This is a classic JOIN query. Whose picture do you want, the sender's or the receiver's? Let's get the picture for the receiver:

SELECT sender, receiver, picture
FROM Friends JOIN Users ON(receiver = username)
WHERE checked = 2;

If you want a specific user only, add the condition sender = 'Jim' or something like that to the query.

You can also JOIN a table twice. Suppose you want to get the picture of both the sender and the receiver:

SELECT sender, receiver, U1.picture AS senderpicture, U2.picture AS receiverpicture
FROM Friends
     JOIN Users AS U1 ON(sender   = U1.username)
     JOIN Users AS U2 ON(receiver = U2.username)
WHERE U2.checked = 2;

SELECT T1.PICTURE
FROM TABLE2 T2
JOIN TABLE1 T1
ON T1.USERNAME = T2.SENDER

You need a join, probably a left join:

SELECT cols, you, want FROM Friends LEFT JOIN Users ON Friends.username=Users.username;