Question

我在下面有几个代码陈述，我试图找到一种方法来使这更简单，更容易。我认为CASE声明是最好的，但经过几天的反复试验，我一直无法弄清楚如何做到这一点。任何和所有的帮助和/或解释将不胜感激。

select Count(lcs.statename)  as [Name 1]
   FROM hsi.itemlc as ilc
   LEFT JOIN hsi.lcstate as lcs on lcs.statenum = ilc.statenum
   where lcs.statename = 'Follow Up'
   AND lcnum = '412'
   AND status = '0'
select Count(lcs.statename)  as [Name 2]
   FROM hsi.itemlc as ilc
   LEFT JOIN hsi.lcstate as lcs on lcs.statenum = ilc.statenum
   where lcs.statename = 'Initial Review'
   AND lcnum = '412'
   AND status = '0'
select Count(lcs.statename)  as [Name 3]
   FROM hsi.itemlc as ilc
   LEFT JOIN hsi.lcstate as lcs on lcs.statenum = ilc.statenum
   where lcs.statename = 'Execution'
   AND lcnum = '412'
   AND status = '0'
select Count(lcs.statename)  as [Name 4]
   FROM hsi.itemlc as ilc
   LEFT JOIN hsi.lcstate as lcs on lcs.statenum = ilc.statenum
   where lcs.statename = 'Holdback'
   AND lcnum = '412'
   AND status = '0'

Answer 1

尝试类似：

SELECT SUM(CASE WHEN lcs.statename = 'Follow Up' THEN 1 ELSE 0 END) as [Name 1],
    SUM(CASE WHEN lcs.statename = 'Initial Review' THEN 1 ELSE 0 END) as [Name 2],
    SUM(CASE WHEN lcs.statename = 'Execution' THEN 1 ELSE 0 END) as [Name 3],
    SUM(CASE WHEN lcs.statename = 'Holdback' THEN 1 ELSE 0 END) as [Name 4]
FROM hsi.itemlc as ilc
LEFT JOIN hsi.lcstate as lcs on lcs.statenum = ilc.statenum
WHERE lcnum = '412'
AND status = '0'

Answer 2

您可以使用SUM（）和CASE：

来完成

SELECT
      SUM(CASE WHEN lcs.statename = 'Follow Up' THEN 1 ELSE 0 END)  as [Name 1],
      SUM(CASE WHEN lcs.statename = 'Initial Review' THEN 1 ELSE 0 END)  as [Name 2],
      ...
   FROM hsi.itemlc as ilc
   LEFT JOIN hsi.lcstate as lcs on lcs.statenum = ilc.statenum
   WHERE lcnum = '412' AND status = '0';

或者，如果您可以阅读多行，则可以使用GROUP BY：

SELECT lcs.statename, COUNT(*) AS num
    FROM hsi.itemlc as ilc
    LEFT JOIN hsi.lcstate as lcs on lcs.statenum = ilc.statenum
    WHERE lcnum = '412' AND status = '0'
    GROUP BY lcs.statename;

会给你类似的东西

Follow Up        25
Initial Review   17
...

Answer 3

您可以将CASE语句与SUM()函数一起使用，如下所示：

SELECT SUM(CASE WHEN lcs.statename = 'Follow Up' THEN 1 ELSE 0 END)  as [Name 1],
       SUM(CASE WHEN lcs.statename = 'Initial Review' THEN 1 ELSE 0 END)  as [Name 2],
       SUM(CASE WHEN lcs.statename = 'Execution' THEN 1 ELSE 0 END)  as [Name 3],
       SUM(CASE WHEN lcs.statename = 'Holdback' THEN 1 ELSE 0 END)  as [Name 4]
FROM hsi.itemlc as ilc
LEFT JOIN hsi.lcstate as lcs on lcs.statenum = ilc.statenum
WHERE lcnum = '412'
  AND status = '0'

导致每个州名的条件计数。

case语句而不是多个选择

3 个答案: