Need to improve the performance of a SQL query - sql

Question

I am new to SQL and I'm facing some problem with the performance of a SQL query.
I followed some points from Google and created the required indexes. But still not able to improve the performance.
Guide me to improve the performance of following the query. The tables have millions of records.
SELECT TOP 15 id,
field1,
field2
FROM (SELECT DISTINCT 0 AS ID,
tblsuites.suite Field1,
'Work Order' AS Field2
FROM tbljb_schedules
INNER JOIN tblsuites
ON tbljb_schedules.tblsuites_id = tblsuites.tblsuites_id
INNER JOIN tblsites
ON tbljb_schedules.tblsites_id = tblsites.tblsites_id
LEFT OUTER JOIN tblbldgs
ON
tbljb_schedules.tblbldgs_id = tblbldgs.tblbldgs_id
WHERE tbljb_schedules.tbldomains_id = 28
AND tbljb_schedules.internalonly = 0
AND tbljb_schedules.tblsites_id IN (SELECT tblsites_id
FROM tbllogins_sites
WHERE tbllogins_id = 264
AND
tblsites.active = 1)
AND ( tblsuites.suite LIKE '%1%' )
UNION
SELECT DISTINCT 0 AS ID,
tblsuites.suite Field1,
'Work Order' AS Field2
FROM arcjb_schedules
INNER JOIN tblsuites
ON arcjb_schedules.tblsuites_id = tblsuites.tblsuites_id
INNER JOIN tblsites
ON arcjb_schedules.tblsites_id = tblsites.tblsites_id
LEFT OUTER JOIN tblbldgs
ON arcjb_schedules.tblbldgs_id =
tblbldgs. tblbldgs_id
WHERE arcjb_schedules.tbldomains_id = 28
AND arcjb_schedules.internalonly = 0
AND arcjb_schedules.tblsites_id IN (SELECT tblsites_id
FROM tbllogins_sites
WHERE tbllogins_id = 264
AND
tblsites.active = 1)
AND ( tblsuites.suite LIKE '%1%' )) T
ORDER BY CASE
WHEN Charindex('1', field1) = 1 THEN 0
ELSE 1
END,
field1

Answer 1

Maybe you should Try the below code changes
SELECT TOP 15
id,
field1,
field2
FROM
(
SELECT
0 AS ID,
tblsuites.suite Field1,
'Work Order' AS Field2,
SeqOne = CASE WHEN CHARINDEX('1', tblsuites.suite)= 1
THEN 1
ELSE 0 END
FROM tbljb_schedules
INNER JOIN tblsuites
ON tbljb_schedules.tblsuites_id = tblsuites.tblsuites_id
INNER JOIN tblsites
ON tbljb_schedules.tblsites_id = tblsites.tblsites_id
LEFT OUTER JOIN tblbldgs
ON tbljb_schedules.tblbldgs_id = tblbldgs.tblbldgs_id
WHERE tbljb_schedules.tbldomains_id = 28
AND tbljb_schedules.internalonly = 0
AND EXISTS -- Replace IN With EXISTS
(
SELECT
1
FROM tbllogins_sites
WHERE tbllogins_id = 264
AND tblsites.active = 1
AND tblsites_id = tbljb_schedules.tblsites_id
)
AND (tblsuites.suite LIKE '%1%')
UNION -- UNION Will By Default Take DISTINCT Records
SELECT
0 AS ID,
tblsuites.suite Field1,
'Work Order' AS Field2,
SeqOne = CASE WHEN CHARINDEX('1', tblsuites.suite)= 1
THEN 1
ELSE 0 END
FROM arcjb_schedules
INNER JOIN tblsuites ON arcjb_schedules.tblsuites_id = tblsuites.tblsuites_id
INNER JOIN tblsites ON arcjb_schedules.tblsites_id = tblsites.tblsites_id
LEFT OUTER JOIN tblbldgs ON arcjb_schedules.tblbldgs_id = tblbldgs.tblbldgs_id
WHERE arcjb_schedules.tbldomains_id = 28
AND arcjb_schedules.internalonly = 0
AND EXISTS
(
SELECT
1
FROM tbllogins_sites
WHERE tbllogins_id = 264
AND tblsites.active = 1
AND tblsites_id = arcjb_schedules.tblsites_id
)
AND (tblsuites.suite LIKE '%1%')
)T
ORDER BY
SeqOne,
field1;

Answer 2

Performance tuning is a more of a trial and error subject.
Looking at your code I can see a major performance offender. This condition in the where clause:
and tblsuites.suite LIKE '%1%'
I don't know how big is the tblSuites table but the use of LIKE '%1%' makes the optimizer perform table scans rather than index seek, so even if you have indexed that column it will be useless.
also follow what #Jayasurya Satheesh mentioned in his answer.