Question

SQL Server beginner here. I am having some trouble on a SELECT/UPDATE statement. I have a table with an order number column and a line number column. The select statement below returns the values I want. I would like to take the result and insert that number into a column on the same table where the order number matches. Am I over thinking this? Or maybe under thinking the complexity? 🙂

    SELECT
    ORDNUM, COUNT(LINNUM) AS 'CountLines'
    FROM [TableName]
    WHERE STS = '3' AND DUEQTY < ONHAND AND STYPE = 'CU'
    GROUP BY ORDNUM

    UPDATE [TableName]
    SET LNCNT = 'CountLines'
    WHERE ORDNUM = ORDNUM

Thank you in advance.
Ben

UPDATE: I used Andomars solution below and it worked great. Thank you all for the assistance.

Answer 1

Using SQL Server syntax:

update  tn
set     LNCNT = SubQuery.CountLines
from    TableName as tn
join    (
        select  ordnum
        ,       count(linnum) as CountLines
        from    TableName
        where   sts = '3'
                and DUEQTY < ONHAND 
                and STYPE = 'CU'
        group by
                ordnum
        ) as SubQuery
on      SubQuery.ordnum = tn.ordnum