How to optimize SQL Server query - sql

Question

I am copying data from one table to another table. While copying I am doing some calculation to modify one column.
SQL Server query:
INSERT INTO rat_proj_duration_map_2
SELECT
r.*,
r.hour_val / (CASE
WHEN week_val = 1 AND
(SELECT TOP 1
hrswk
FROM UserProfileRATinterface_view us
INNER JOIN users u
ON u.username = us.username
WHERE calwk = 2
AND r.uid = u.uid
AND yr = 2016)
> 0 THEN (SELECT TOP 1
hrswk
FROM UserProfileRATinterface_view us
INNER JOIN users u
ON u.username = us.username
WHERE calwk = 2
AND r.uid = u.uid
AND yr = 2016)
WHEN (SELECT
hrswk
FROM UserProfileRATinterface_view us
INNER JOIN users u
ON u.username = us.username
WHERE r.week_val = us.calwk
AND r.uid = u.uid
AND yr = 2016)
< 1 AND
(SELECT
MAX(hrswk)
FROM UserProfileRATinterface_view us
INNER JOIN users u
ON u.username = us.username
WHERE r.uid = u.uid
AND yr = 2016)
> 0 THEN (SELECT
MAX(hrswk)
FROM UserProfileRATinterface_view us
INNER JOIN users u
ON u.username = us.username
WHERE r.uid = u.uid
AND yr = 2016)
WHEN (SELECT
COUNT(*)
FROM UserProfileRATinterface_view us
INNER JOIN users u
ON u.username = us.username
WHERE r.uid = u.uid
AND yr = 2016)
<= 0 THEN 1
ELSE (SELECT
hrswk
FROM UserProfileRATinterface_view us
INNER JOIN users u
ON u.username = us.username
WHERE r.week_val = us.calwk
AND r.uid = u.uid
AND yr = 2016)
END) * 100 AS percentage_val
FROM rat_proj_duration_map r
When I run this query I getting time out issue.
TCP Provider: Timeout error [258]
SQL Server is not in my hand to increase time out value.
Is it possible to optimize my SQL query?

Answer 1

Are you sure this query is logically correct? You have several TOP 1s without specific ORDER BY, scalar comparison of subselect without TOP (which, I assume, may return more than one row if you are using top in other subselects with same source).
And yes - this query can be optimized. You can obtain all the values you need with a single subselect statement and avoid multiple execution of same subselects for each row of rat_proj_duration_map which you are having now:
INSERT INTO rat_proj_duration_map_2
SELECT
r.*,
r.hour_val / (CASE
WHEN week_val = 1 AND us.min_hrswk_2 > 0
THEN us.min_hrswk_2
WHEN us.min_hrswk_week_val <1
AND max_hrswk > 0
THEN max_hrswk
WHEN us.cnt <= 0
THEN 1
ELSE min_hrswk_week_val
END) * 100 as percentage_val
FROM
rat_proj_duration_map r
OUTER APPLY
(
SELECT
count(*) as cnt,
MIN(CASE WHEN calcw = 2 THEN hrswk END) as min_hrswk_2,
MIN(CASE WHEN calcw = r.week_val THEN hrswk END) as min_hrswk_week_val,
MAX(hrswk) as max_hrswk
FROM UserProfileRATinterface_view us
inner join users u on u.username=us.username
WHERE r.uid=u.uid and yr=2016
) us
But I can't be sure if original logic is correct. And the idea of that case to me looks like this:
...
r.hour_val / COALESCE(NULLIF(us.min_hrswk_2, 0),
NULLIF(us.min_hrswk_week_val, 0), NULLIF(max_hrswk, 0), 1)
...

Answer 2

The subqueries in your case clause seem to be essentially the same. You could simplify the whole command by defining a grouped version (... where yr=2016 group by u.uid) of this subquery (preferrably as a common table expression) and then work with that. This could potentially save a lot of redundant operations.
The following might work (have not tested it):
;WITH usrall as (
SELECT u.uid ui, hrswk hw, r.week wk, us.calwk cw
FROM UserProfileRATinterface_view us
INNER JOIN users u on u.username=us.username
WHERE r.uid=u.uid and yr=2016
), usrgrp as (
SELECT ui gui, MAX(hrswk) ghw, count(*) gcnt FROM usrall group by ui
), denom as (
SELECT gui dui, COALESCE( MAX(w2.hw), MAX(wkwc.hw), MAX(gwh) ) dnm
FROM usrgrp
LEFT JOIN usrall w2 ON w2.ui=gui AND w2.cw=2 AND w2.hw>0
LEFT JOIN usrall wkcw ON wkcw.ui=gui AND wkcw.wk=wkcw.cw AND wkwc.hw<1
GROUP BY gui
)
SELECT r.*, r.hour_val / d.dnm
FROM rat_proj_duration_map r
INNER JOIN denom d ON d.dui=u.uid
Essentially I have tried (I hope it works :-/) to replace the case construct by a COALESCE() function that checks the three possible calculated values one after the other. The first non-null value is accepted.
As I said: I have not tested it. Good luck