案例陈述，而不是多个选择

我有几个代码声明如下，我想找出一种方法，使这更简单和更容易。我会假设CASE声明是最好的，但经过几天的试验和错误之后，我一直无法弄清楚如何去做。任何和所有的帮助和/或解释将不胜感激。案例陈述，而不是多个选择

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'

来源

2012-10-16 John

*** SQL ***只是*结构化查询语言* - 许多数据库系统使用的语言，但不是数据库产品......语法细节是供应商特定的 - 所以我们真的需要知道什么**数据库系统**（和哪个版本），你正在使用...... –

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'

来源

2012-10-16 16:46:16

这工作完美...几天下来，但感谢一百万 – John

现在，如果我要添加其他列......我收到了“消息8120，级别16，状态1，行1 列'hsi.itemlc.itemnum'在选择列表中无效，因为它不包含在聚合函数或GROUP BY子句中。”试图在SELECT后添加 ilc.itemnum as [test]时出错 – John

@John您必须将GROUP BY添加到该列中。 –

您可以用SUM（做）和CASE：

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，如果你能读多行，你可以使用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;

哪会给哟ü像

Follow Up  25 
Initial Review 17 
...

来源

2012-10-16 16:46:41 LSerni

可以使用CASE语句与SUM()功能，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'

这导致每个州的名字条件计数。

来源

2012-10-16 16:47:20

案例陈述，而不是多个选择

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