Question

I have problems to query my data. Here are my tables:

CREATE TABLE `A` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `myString` varchar(10) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

CREATE TABLE `B` (
  `id` int(10) NOT NULL AUTO_INCREMENT,
  `myStringId1` int(10) NOT NULL,
  `myStringId2` int(10) NOT NULL,
  `value` varchar(10) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `index1` (`myStringId1`),
  KEY `index2` (`myStringId2`),
  CONSTRAINT `fk_B2` FOREIGN KEY (`myStringId2`) REFERENCES `A` (`id`),
  CONSTRAINT `fk_B1` FOREIGN KEY (`myStringId1`) REFERENCES `A` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

where myStringId1 and myStringId2 have foreign key constraints to TABLE A (id)

Ok let me clarify what I want to achieve by query:
Lets assume some values for the given tables:

TABLE A:
ROW1: 22, "foo"
ROW2: 33, "bar"

TABLE B: 
ROW1: 1, 22, 33, "true"
ROW2: 2, 22, 22, "false"

Now what I need is a query where I give String “foo” and get the following result from joining the two tables:

RESULT:
ROW1: "foo","bar", "true"
ROW2: "foo", "foo", "false"

given String “bar” I expect this:

RESULT:
ROW1: “foo”,”bar”,”true”

any ideas ?

Answer 1

After reading your comment I think this is closer to what you need:

SELECT a1.myString as myString1, a2.myString as myString2, b.value
FROM `B` b
    JOIN `A` a1 on a1.id = b.myStringId1
    JOIN `A` a2 on a2.id = b.myStringId2
WHERE a1.myString = 'SOME STRING' OR a2.myString = 'SOME STRING'

The two joins will ensure the both b.myStringId1 and b.myStringId2 are existing keys for TABLE A, and the WHERE ensures that one of those 2 strings is the one you need.