如何計算兩列中具有相同值的行，並僅返回count計數的行

Question

關於這個問題： 如何計算兩列中具有相同值的行（SQL）？

有沒有辦法只返回計數<3的行？

+-----+-----+-----+
|  A  |  B  |count|
+=====+=====+=====+
|  1  |  3  |  2  |
+-----+-----+-----+
|  4  |  2  |  1  |
+-----+-----+-----+

Answer 1

HAVING子句

 SELECT ...
 FROM ...
 WHERE ...
 GROUP BY whatever
 HAVING count(*) <3

Answer 2

只需在HAVING子句中添加條件即可

SELECT colName, COUNT(*)
FROM tableName
GROUP BY colName
HAVING COUNT(*) < 3