SELECT a,nb FROM t1 JOIN (SELECT c AS a,COUNT(*) AS nb FROM t1 GROUP BY c) AS t2 USING(a)
Sans perdre les ligne qui dont le COUNT(*) retournerait 0.
Une idée ?
En faisant LEFT JOIN, j'obtiens la valeur NULL pour nb, mais j'aimerais obtenir 0.
SELECT a,nb FROM t1 JOIN (SELECT c AS a,COUNT(*) AS nb FROM t1 GROUP BY c) AS t2 USING(a)