Question

表T中有A、B、C三列,用SQL语句实现:当A列大于B列时选择A列否则选择B列(作为结果集

Answer 1

SELECT CHOOSE((A>B)+2,A,B) AS result FROM T;

Answer 2

直接使用union好像可以实现俩表联合查询并去掉重复返回一个集

把这个结果集再当成一个表

SELECT NAME,COUNT(*) FROM (结果集语句) A
GROUP BY NAME

Answer 3

SELECT CASE WHEN A > B THEN A ELSE B END AS RESULT FROM T

Answer 4

SELECT CASE WHEN A > B THEN A ELSE B END AS RESULT FROM T