Question

Below I am trying to update value of a parent table from child table and counting matching values. Tables in my db:

1. issue_dimension with id = issue_id and have column accno.

2. star_schema with id star_id,this Child column have fk issue_id and column book_frequency

The book_frequency need to match the count of each accno in parent table , I tried this

update [test1] .[dbo] .star_schema 
set [book_frequency] = (
    select top 1 COUNT([issue_dimension].ACCNO)as book_frequency 
    from issue_dimension 
    group by ACCNO having (COUNT(*)>1) and 
        issue_dimension.ACCNO = star_schema .ACCNO
)

It only updates only 1st value count issue_dimension. I need to count every accno in issue_dimension and update it to matching accno of star_schema.
I never did update by joining two or more tables , can anyone help in this with joins

Answer 1

UPDATE s
SET [book_frequency] = i.CNT
FROM [test1].[dbo].star_schema s
    INNER JOIN 
    ( 
        SELECT ACCNO, COUNT(*) as CNT
        FROM issue_dimension 
        GROUP BY ACC_NO
        HAVING COUNT(*)>1
    ) i on (s.ACCNO = i.ACCNO)

I didn’t check it but it should works