mysql query taking long time to excute - mysql

Question

This is my query taking 3 second to execute :
SELECT I.itemname,
I.overdue,
D.value,
I.itemid,
icd.ecwstatus AS status,
C.inactiveflag AS inactive,
icd.validfrom,
icd.validto
FROM items I
JOIN itemdetail D
ON I.itemtype = 'I'
AND I.itemid = D.itemid
AND D.propid = 13
LEFT OUTER JOIN icd
ON icd.code = D.value
LEFT OUTER JOIN edi_icdcodes C
ON I.itemid = C.itemid
WHERE I.deleteflag = 0
AND ( icd.validfrom <= '2012-12-06'
OR icd.validfrom IS NULL )
AND ( icd.validto >= '2012-12-06'
OR icd.validto IS NULL )
AND I.itemname LIKE 'A%'
AND ( I.keyname = 'Assessments' )
ORDER BY I.itemname ASC limit 0,6;
i have index IX_items_itemType_deleteFlag_keyName_itemName on multiple column itemType , deleteFlag ,keyName ,itemName in items table and also have index on other table's column which used in join and where clause.
so how can i improve performance of query ?
Thanks

Answer 1

I would have an index on your items table based on the multiple key columns used for your where clause and order by. I would have the index with the smallest result set in the front position. For example, you are specifically looking for "Assessments". If your table has 1 million records, and 600k of them are of item type "I", but only 5k are "Assessments", then the smallest part up front might be better for your query TO process.
I would have your:
items table indexed on ( keyname, itemtype, deleteflag, itemname )
ItemDetail table, indexed ON ( itemid, propid )
icd table indexed ON ( code, validfrom, validto, ecwstatus )
edi_icdcodes table index ON (itemid)
SELECT
I.itemname,
I.overdue,
D.value,
I.itemid,
icd.ecwstatus AS status,
C.inactiveflag AS inactive,
icd.validfrom,
icd.validto
FROM
items I
JOIN itemdetail D
ON I.itemid = D.itemid
AND D.propid = 13
LEFT OUTER JOIN icd
ON D.value = icd.code
AND ( icd.validfrom <= '2012-12-06'
OR icd.validfrom IS NULL )
AND ( icd.validto >= '2012-12-06'
OR icd.validto IS NULL )
LEFT OUTER JOIN edi_icdcodes C
ON I.itemid = C.itemid
WHERE
I.itemtype = 'I'
AND I.deleteflag = 0
AND I.keyname = 'Assessments'
AND I.itemname LIKE 'A%'
ORDER BY
I.itemname ASC
LIMIT
0,6;
Note... if the ICD table will always have a value for both from/to dates when records are created, you won't need to test for NULL, but do understand why you had that via left-join and putting in the where clause. So, that part might be simplified to
LEFT OUTER JOIN icd
ON D.value = icd.code
AND icd.validfrom <= '2012-12-06'
AND icd.validto >= '2012-12-06'

Answer 2

What you do there, it's that you use a basic table, then you do some 'join' and only after, you do your 'where' requests . To go quicky, try to include your condition in your 'joins'. In this manneer, it selects the different lines in the 'join' request and not after.
SELECT I.itemname,
I.overdue,
D.value,
I.itemid,
icd.ecwstatus AS status,
C.inactiveflag AS inactive,
icd.validfrom,
icd.validto
FROM items I
JOIN itemdetail D
ON I.itemtype = 'I'
AND I.itemid = D.itemid
AND D.propid = 13
AND I.deleteflag = 0
LEFT OUTER JOIN icd
ON icd.code = D.value
AND ( icd.validfrom <= '2012-12-06'
OR icd.validfrom IS NULL )
AND ( icd.validto >= '2012-12-06'
OR icd.validto IS NULL )
LEFT OUTER JOIN edi_icdcodes C
ON I.itemid = C.itemid
AND I.itemname LIKE 'A%'
AND ( I.keyname = 'Assessments' )
ORDER BY I.itemname ASC limit 0,6;