php - MySQL count rows where a=b and b=a -

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This is the first time I have asked a question. This is the first time that I can not find what I am seeing and I think I am being mad because it should be simple!

Assume that you have a MySQL table, 'T' with two columns 'A', 'B'. 

  AB --- 1 2 2 1 1 3 3 1 2 4   
 I like to count a variable given interrelationship. Therefore if I should  
  X = 1   
 return it  
  2   
 Because 1, 2 and 2, 1 is present, and 1, 3 and 3, 1 exists, however, supply  
  x = 2   
 It should be returned  
  1   
 because 1, 2 and 2, 1 exists but no other rows, where 2 = n AND N = 2  
 I hope this is clear! And sorry if it is easy, I think the brain is getting freeze .. Cheers!   
 
 
 This will work (but if you have a line with (n, n) then also Will be counted as a mutual relationship):  
  select count (*) Join TT1 t1.B = T2.A on T2 where t1.A =? And t2.b =?   
 (assign values ​​to both standards)

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