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我正試圖在DB2中優化這個查詢。用於選擇url關鍵字的內部查詢從15秒到大約10分鐘查詢。我追蹤了這個問題,它似乎是因爲'urlkeyword = c.catentry_id'比較varchar字段(urlkeyword)和bigint字段的比較。如果我修改它以將varachar與字符串值進行比較,則它會變得更快。我的問題是:爲DB2優化查詢 - 如何從bigint轉換爲varchar/char?
什麼是將c.catentry_id從bigint轉換爲varchar的語法? (我想如果我能做到這一點,將修復它)
select
xmlelement(NAME "Products",xmlagg(xmlrow(c.field5 as "ExternalId",
cd.name as "Name",
cg.identifier as "CategoryExternalId",
concat('@[email protected]', cd.thumbnail) as "ImageUrl",
(select urlkeyword from seourl s
inner join seourlkeyword sk
on s.seourl_id = sk.seourl_id
where urlkeyword = c.catentry_id
) as "ProductPageUrl",
mfpartnumber as "ManufacturerPartNumber",
cd.shortdescription as "Description",
c.field1 as "BrandExternalId" option row "Product"))) as xml_document
from catentry c
inner join catentdesc cd
on c.catentry_id = cd.catentry_id and cd.language_id = -1
inner join catgpenrel cgp
on c.catentry_id = cgp.catentry_id
inner join catgroup cg
on cg.catgroup_id = cgp.catgroup_id
where cgp.catalog_id in
(select catalog_id from catalog where identifier = 'Web_OW Default Web')
感謝它的作品,雖然我只是鑄造char。該表是索引,但索引掃描,無論出於什麼原因都將左側(字符串轉換爲數字),而不是轉換右側。所以鑄造右側的力量的行爲。這工作,查詢現在回到15秒... –