How to query for One - Many Relation

Question

I have two database tables with "one to many" relationship

let say, table A and Table B

One field from Table A is a foreign key in table BI wanna fetch just one record from table A as well as table B (given table A's primary key)

table A

id                name
--------------------
1                 ABC
2                 XYZ

Table B

id              A_id                      email
------------------------------------------------
1                 1                 temp@temp1.com
2                 1                 temp@temp2.com
3                 1                 temp@temp3.com
4                 2                 temp@temp4.com
4                 2                 temp@temp5.com

Answer should be like this (Single Record From Table B)

For a.id = 1

A.id, A.name,B.email
-------------------------
1, ABC, temp@temp1.com

For a.id = 2

A.id, A.name,B.email
-------------------------
1, XYZ, temp@temp4.com

I used this query, but it returns all the records from table B(as table B has multiple records for each record in Table A)

SELECT a.id,a.name, b.email FROM A a, B b WHERE a.id = 1 AND b.A_id = a.id

Answer 1

Try a JOIN

SELECT 
    a.id,
    a.name,
    b.email 
FROM A a
LEFT JOIN B b ON b.A_id = a.id
WHERE a.id = 1;
GROUP BY b.A_id

More info on JOINS

Answer 2

I have created a SQL Fiddle for the demo here: http://www.sqlfiddle.com/#!2/15ae7/5

The query that you can use for getting the desired output is:

SELECT 
tableA.id,
tableA.name,
tableB.email 
FROM tableA
LEFT OUTER JOIN tableB ON tableB.A_id = tableA.id
GROUP BY tableB.A_id;

For more information on JOINS and GROUP BY you can refer to the following pages:

http://dev.mysql.com/doc/refman/5.0/en/join.html

https://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html

Answer 3

You can use LIMIT if you want only one record.

SELECT a.id,a.name, b.email FROM A a, B b WHERE a.id = 1 AND b.A_id = a.id LIMIT 0,1

Hope this helps you.