sql - Performance impact due to Join -

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i have 2 tables product , account.

product table columns 

product_id   (pk)                       subscription_id

account table columns

account_nbr subscription_id     (account_nbr , subscription_id primary key columns in account table) ... other columns

i have find account_nbr , subscription_id product_id.

i product_id input. using can subscription_id product table , using subscription_id can account_nbr value account table.

instead of getting info in 2 queries, can done in 1 query?

something below:

select distinct a.acct_nbr,p.subscription_id  account  a,product p v.product_id = ' val 1' ,  v.subscription_id  = p.subscription_id

will performance of above query low compared 2 separate queries?

i have find account_nbr , subscription_id product_id.

so, you're correct in approach need join 2 result-sets together:

select p.account_nbr, p.subscription_id   account   join product p     on a.subscription_id = p.subscription_id  p.product_id = :something

some points:

  1. you have alias v in query; don't know came from.
  2. learn use ansi join syntax; if make mistake it's lot more obvious.
  3. you're selecting a.acct_nbr, doesn't exist as-is.
  4. there's no need distinct. account_nbr , product_id primary key of account.

will performance of above query low compared 2 separate queries?

probably not. if query correct , tables correctly indexed it's highly unlikely whatever you've coded beat sql engine. database designed select data quickly.


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