SQL ()为3列返回错误的结果

Question

我正在编写一个应该给我一个count()和三个avg()的查询。count()工作正常，但是avg()函数返回错误的结果。我处理的数据如下所示：

MD Name |    PT | Med Staff | LOS | DRG Bench | LOS - Bench
MCP     | 12345 | Ortho SX  |  5  |    4      |       1
MCP     | 25879 | Ortho SX  |  3  |    5      |      -2
MCP     | 98556 | Ortho SX  |  4  |    5      |      -1
... 

我想要的输出是：

MD Name | # PT | Med Staff | Avg LOS | Avg DRG Bench | AVG LOS - Bench
MCP     |   3  | Ortho SX  |    4    |       4.66    |       0

我得到了不正确的平均数结果。我有一个特别的案件，我有以下情况：

MD Name | LOS    | Bench  | LOS - Bench
MCP     | 2.0000 | 1.8000 |    0.2000
MCP     | 1.0000 | 1.7000 |   -0.7000
MCP     | 25.0000| 4.9000 |   20.1000
MCP     | 4.0000 | 2.2000 |    1.8000

对于AVG，我得到9.000000而不是8.000000，对于AVG工作台，我得到2.780000而不是2.65，而对于LOS-Bench，我得到6.220000而不是5.35，这些都是显著的差异，我必须正确到两位小数点。

下面是我正在使用的SQL，Server 2008

DECLARE @STARTDATE DATETIME
DECLARE @ENDATE DATETIME

SET @STARTDATE = '2013-05-01'
SET @ENDATE = '2013-05-31'

SELECT DISTINCT pv.pract_rpt_name AS 'PHYSICIAN'
, COUNT(DISTINCT vr.pt_id) AS '# PTS' 
--, pv.spclty_desc AS 'SPECIALTY'
, pv.med_staff_dept AS 'MED STAFF'
, AVG(vr.len_of_stay) AS 'LOS'
, AVG(vr.drg_std_days_stay) AS 'DRG LOS BENCH'
, AVG(vr.len_of_stay - vr.drg_std_days_stay) AS 'LOS - DRG BENCH'

FROM smsmir.vst_rpt vr
LEFT OUTER JOIN smsmir.pyr_plan pp <-- removed and fixed
ON vr.pt_id = pp.pt_id <-- removed and fixed
JOIN smsdss.pract_dim_v pv
ON vr.adm_pract_no = pv.src_pract_no

WHERE vr.adm_dtime BETWEEN @STARTDATE AND @ENDATE
AND vr.vst_type_cd = 'I'
AND pv.spclty_desc != 'NO DESCRIPTION'
--AND pv.spclty_desc NOT LIKE 'HOSPITALIST%'
AND vr.drg_std_days_stay IS NOT NULL
AND pv.pract_rpt_name != '?'
AND pv.orgz_cd = 's0x0'
AND pv.med_staff_dept IN (
'INTERNAL MEDICINE',
'FAMILY PRACTICE',
'SURGERY'
)
GROUP BY pv.pract_rpt_name, pv.med_staff_dept
ORDER BY pv.med_staff_dept, AVG(vr.len_of_stay - vr.drg_std_days_stay)DESC

谢谢你的时间和努力。

Answer 1

查询中的外部联接可能会影响AVG函数正在操作的行数。如果您不需要它(我在查询的其他地方看不到引用该表的任何地方)，请尝试删除它。

Answer 2

唯一的可能是在表中选择的行中存在NULL.如果有空列，AVG将忽略它，而不是计数它.

DECLARE @STARTDATE DATETIME
DECLARE @ENDATE DATETIME

SET @STARTDATE = '2013-05-01'
SET @ENDATE = '2013-05-31'

SELECT DISTINCT pv.pract_rpt_name AS 'PHYSICIAN'
, COUNT(DISTINCT vr.pt_id) AS '# PTS' 
--, pv.spclty_desc AS 'SPECIALTY'
, pv.med_staff_dept AS 'MED STAFF'
, AVG(ISNULL(vr.len_of_stay,0)) AS 'LOS'
, AVG(ISNULL(vr.drg_std_days_stay,0)) AS 'DRG LOS BENCH'
, AVG(ISNULL((vr.len_of_stay - vr.drg_std_days_stay),0)) AS 'LOS - DRG BENCH'

FROM smsmir.vst_rpt vr
LEFT OUTER JOIN smsmir.pyr_plan pp
ON vr.pt_id = pp.pt_id
JOIN smsdss.pract_dim_v pv
ON vr.adm_pract_no = pv.src_pract_no

WHERE vr.adm_dtime BETWEEN @STARTDATE AND @ENDATE
AND vr.vst_type_cd = 'I'
AND pv.spclty_desc != 'NO DESCRIPTION'
--AND pv.spclty_desc NOT LIKE 'HOSPITALIST%'
AND vr.drg_std_days_stay IS NOT NULL
AND pv.pract_rpt_name != '?'
AND pv.orgz_cd = 's0x0'
AND pv.med_staff_dept IN (
'INTERNAL MEDICINE',
'FAMILY PRACTICE',
'SURGERY'
)
GROUP BY pv.pract_rpt_name, pv.med_staff_dept
ORDER BY pv.med_staff_dept, AVG(vr.len_of_stay - vr.drg_std_days_stay)DESC