how to optimized without union clauses? - sql

Question

Is it possible to write below query without a union clause.
select ProductId,ImageName,ImageType, ROW_NUMBER() over (order by ProductId desc) RowId
from
(
select p.id ProductId ,p.pic_image ImageName,'pic_image' ImageType
from product p
left outer join iimages_edited pe on p.id = pe.[id]
where isnull(p.pic_image,'') <> '' and isnull(pe.pic_image,0)=0
union
select p.id ProductId,p.pic_bimage ImageName,'pic_bimage' ImageType
from product p
left outer join iimages_edited pe on p.id = pe.[id]
where isnull(p.pic_bimage,'') <> '' and isnull(pe.pic_bimage,0)=0
union
select p.id ProductId,p.pic_limage ImageName,'pic_limage' ImageType
from product p
left outer join iimages_edited pe on p.id = pe.[id]
where isnull(p.pic_limage,'') <> '' and isnull(pe.pic_limage,0)=0
union
select p.id ProductId,p.pic_blimage ImageName,'pic_blimage' ImageType
from product p
left outer join iimages_edited pe on p.id = pe.[id]
where isnull(p.pic_blimage,'') <> '' and isnull(pe.pic_blimage,0)=0
union
select p.id ProductId,p.pic_cimage ImageName,'pic_cimage' ImageType
from product p
left outer join iimages_edited pe on p.id = pe.[id]
where isnull(p.pic_cimage,'') <> '' and isnull(pe.pic_cimage,0)=0
)t
Above query has same table but different where condition, It is
possible to do it in a single query ?
Any help will be much appreciated !
Thanks in advance

Answer 1

It seems that you are repeating the same join and filters with differents columns each time. You can convert them to rows using UNPIVOT, on each table, before the join :
select pe.ProductId, p.ProductId, p.ImageName, p.ImageType, ROW_NUMBER()
over (order by p.ProductId desc) RowId
from (
select id as ProductId, ImageType, ImageName
from product
unpivot (
ImageType for ImageName
in (pic_image, pic_bimage, pic_limage, pic_blimage, pic_cimage)
) t
) as p
left outer join (
select id as ProductId, ImageType, ImageName
from iimages_edited
unpivot (
ImageType for ImageName
in (pic_image, pic_bimage, pic_limage, pic_blimage, pic_cimage)
) t
) as pe
on p.ImageType = pe.ImageType
and p.ProductId = pe.ProductId
where pe.ProductId is null
UNPIVOT filters null values, so ISNULL are probably not necessary.