使用SQL比較2個不同表中的字段

Question

我想比較聯系表中的地址字段是否與交付表的地址字段不同。

SELECT contactID, addressline1
FROM contact
where contactID = '0018319'

以下是包含舊詳細信息的交付表。

SELECT contactID, addressline1
FROM delivery
where contactID = '0018319'

Answer 1

SELECT contactID, d.addressline1, c.addressline1
FROM delivery d
INNER JOIN contact c on d.contactID = c.contactID
where d.addressline1 != c.addressline1

Answer 2

如果要返回一個標志，那么你將在select語句中使用case ：

select contactId,
       (case when d.addressline1 = c.addressline1 or d.addressline1 is null and c.addressline1 is null
             then 'SAME'
             else 'DIFFERENT'
        end) as SameOrDifferent
from contact c join
     delivery d
     on c.contactId = d.contactId
where contactId = '0018319';

這將比較兩個表中的每個地址。

如果您想知道是否所有內容都相同，那么查詢會更復雜。 我們的想法是在addressline1上的兩個表（對於給定的contractid ）之間進行full outer join 。 如果所有地址行都匹配，則full outer join將永遠不會產生NULL值。 如果缺少任何一個（在任何一側），那么將有NULL值。

select coalesce(c.contactId, d.contactId) as contactId,
       (case when sum(case when c.addressline1 is null or d.addressline1 is null
                           then 1
                           else 0
                       end) = 0
             then 'SAME'
             else 'DIFFERENT'
        end) as SameOrDifferent
from (select c.* from contact c where c.contactId = '0018319') c full outer join
     (select d.* from delivery d where d.contactId = '0018319') d
     on c.addressline1 = d.addressline1 and
        c.contactId = d.contactId  -- not actually necessary but useful for multiple contacts
group by coalesce(c.contactId, d.contactId)