How can I make this SQL query more efficient? - sql

Question

I have a query trying to pull data from multiple tables but when I run it, it takes a really long time (So long I haven't even been able to wait long enough). I know it's extremely inefficient and wanted to get some input as to how it can be written better. Here it is:
SELECT
P.patient_name,
LOH.patient_id,
LOH.requesting_location,
LOH.sample_date,
LOH.lab_doing_work,
L.location_name,
LOD.test_code,
LOD.test_rdx,
LSR.tube_type
FROM
mis_db.dbo.lab_order_header AS LOH,
mis_db.dbo.patient AS P,
mis_db.dbo.lab_order_detail AS LOD,
mis_db.dbo.lab_sample_rule AS LSR,
mis_db.dbo.location AS L
WHERE
LOH.requesting_location = '000839' AND
LOH.lab_order_id = LOD.lab_order_id AND
LOH.sample_date IN ('05/28/2015', '05/29/2015')
--LOH.patient_id = LOD.patient_id
--LOD.sample_date = LOH.sample_date
ORDER BY
P.patient_name DESC

Answer 1

try this (or something like it)
SELECT P.patient_name,
lo.patient_id, lo.requesting_location,
lo.sample_date, lo.lab_doing_work,
l.location_name, d.test_code, d.test_rdx,
d.tube_type
FROM mis_db.dbo.lab_order_header lo
join mis_db.dbo.patient p on p.patient_id = lo.Patient_id
join mis_db.dbo.lab_order_detail d on d.lab_order_id = lo.lab_order_id
join mis_db.dbo.lab_sample_rule r on r.rule_id = lo.ruleId -- ????
join mis_db.dbo.location l on l.locationid = lo.requesting_location
WHERE lo.requesting_location = '000839' AND
lo.sample_date IN ('05/28/2015', '05/29/2015')
ORDER BY p.patient_name DESC

Answer 2

I ended up going with the following and was able to get the results I wanted:
SELECT LOH.patient_id,
patient_name,
[mis_db_rpt].[common].[string_date_format](LOD.sample_date) AS
[Draw Date],
test_description,
LOD.test_code,
LOH.lab_doing_work,
tube_type,
L.short_name
FROM [mis_db].[dbo].[lab_order_header]
LOH
INNER JOIN
[mis_db].[dbo].[lab_order_detail]
LOD
ON LOH.lab_order_id = LOD.lab_order_id
INNER JOIN
[mis_db].[dbo].[patient]
P
ON P.patient_id = LOD.patient_id
INNER JOIN
[mis_db].[dbo].[sample_tube]
ST
ON LOD.sample_id = ST.sample_id
INNER JOIN
[mis_db].[dbo].[location] AS
L
ON LOH.lab_doing_work = L.location_id
INNER JOIN
[mis_db].[dbo].[lab_test] AS
LT
ON LOD.test_code = LT.test_code
WHERE LOH.requesting_location = '000839' AND
LOD.sample_date IN ('05/28/2015', '05/29/2015')
ORDER BY LOD.sample_date,
patient_name,
LOD.patient_id,
test_description

Answer 3

I would try
Click to run the estimated execution plan in SSMS and see if it suggests any missing indexes. I would think a non clustered index on lo.requesting_location and sample_date might help with the filter
Also in desc index on p.patient_name may help with the performance of the order by.
Try changing the IN date filter to "between '05/28/2015' and '05/29/2015'