SQL脚本 CASE...WHEN...THEN...ELSE...END 的应用

--查找含有A 或 C 站点的车次
drop table SCHEDULETEST;

create table SCHEDULETEST
(
  SID     int not null,
  CHECI   VARCHAR(8),
  CHEZHAN VARCHAR(8)
);

新增示例数据

Code

select * from scheduletest;

SELECT CHECI as \'经过A和C站点的车次\'
FROM SCHEDULETEST
WHERE CHEZHAN IN(\'A\',\'C\')
GROUP BY CHECI
HAVING COUNT(distinct SID)>=2;

SELECT CHECI
FROM SCHEDULETEST A
WHERE (CHEZHAN=\'A\' OR CHEZHAN=\'C\')
GROUP BY CHECI
HAVING COUNT(distinct SID)>=2;

--取出每一车次停靠的站点数
select checi \'车次\',count( distinct chezhan) AS \'停靠站点数量\'
from SCHEDULETEST
group by checi;

--取出每一车次停靠 A,C的站点次数
select checi AS 车次,
SUM(case chezhan when \'A\' THEN 1 ELSE 0 END) \'停靠A站点的次数\',
SUM(case chezhan when \'C\' THEN 1 ELSE 0 END) \'停靠C站点的次数\'
FROM SCHEDULETEST
GROUP BY CHECI;