Select correct MySQL record with multiple records

Question

I have a pain finding the correct MySQL statement.

Records are like

id    leadid    fieldnumber    value
1     1         100            AAA
2     1         101            yes
3     1         102            email1
4     2         100            AAA
5     2         101            no
6     2         102            email2
7     3         100            BBB
8     3         101            yes
9     3         102            email3
10    4         100            AAA
11    4         101            yes
12    4         102            email4

Now I want to collect from every unique leadid the value column from the record with fieldnumber = 102 where the corresponding records with the same leadid satisfy:

(fieldnumber = 100 AND value = "AAA") AND 
(fieldnumber = 101 AND value = "yes")

In this example this results in: email1, email4

I got already result with the first selection statement ( fieldnumber = 100 AND value = "AAA" ) but when I add the second one ( fieldnumber = 101 AND value = "yes" ), the result is always zero records.

I suppose it's a stupid thing, but I can't figure out or find the correct statement to do so.

Answer 1

The key point here is to recognize that you are working with three records from the same table at the same time. You have to join the table with itself, twice — these are called self-joins .

You need something like:

SELECT a3.value
  FROM Anonymous_Table AS a1
  JOIN Anonymous_Table AS a2 ON a1.leadid = a2.leadid
  JOIN Anonymous_Table AS a3 ON a1.leadid = a3.leadid
 WHERE (a1.fieldnumber = 100 AND a1.value = "AAA")
   AND (a2.fieldnumber = 101 AND a2.value = "yes")
   AND (a3.fieldnumber = 102)