表中有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,当B列大于C列时选择B列否则选C
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1:
DELIMITER
//
CREATE PROCEDURE ProcOut()
BEGIN
DECLARE EXIT
HANDLER FOR SQLEXCEPTION BEGIN END;
DECLARE Sum_a INT(11);
DECLARE Sum_b INT(11);
DECLARE Sum_c INT(11);--
获取A列中的总值 <--
DECLARE cur_1 CURSOR FOR SELECT SUM(A) FROM table_name;
OPEN cur_1;
FETCH cur_
1 INTO Sum_a;
CLOSE cur_1;
-- 获取B列中的总值
<--
DECLARE cur_2 CURSOR FOR SELECT SUM(B) FROM table_name;
OPEN cur_2;
FETCH cur_
2 INTO Sum_b;
CLOSE cur_2;
-- 获取C列中的总值
<--
DECLARE cur_3 CURSOR FOR SELECT SUM(C) FROM table_name;
OPEN cur_3;
FETCH cur_
3 INTO Sum_c;
CLOSE cur_3;
IF Sum_a
>
Sum_b THEN
SELECT A
FROM table_name;
ELSEIF Sum_b
> Sum_c THEN
SELECT B FROM table_name;
ELSE
SELECT C FROM table_name;
END IF;;
END;//
CALL
ProcOut()//
2:
select
case
when A>B then
case when A>C then A
else C end
else
case when B>C then B else C
end
end as name
from member
3:
select
(case when A>B then A else B end) as 'A’ ,
(case when B>C then B else C end) as 'B' from Person;