これらの3つのテーブルがある場合(UNIONを学習するための単なる例ですが、これらは実際のテーブルではありません):
列のあるテーブル:
Customer:
id | name | order_status
Order_Web:
id | customer_id | order_filled
Order:
id | customer_id | order_filled
そして、Unionを使用してその顧客のOrder_WebテーブルまたはOrderテーブルのいずれかに注文が入力されたときに、Customerテーブルのorder_statusを更新したいと思いました。
UPDATE c
SET c.order_status = 1
FROM Customer AS c
INNER JOIN Order_Web As ow
ON c.id = ow.customer_id
WHERE ow.order_filled = 1
UPDATE c
SET c.order_status = 1
FROM Customer AS c
INNER JOIN Order As o
ON c.id = o.customer_id
WHERE o.order_filled = 1
Order_webとorderでUnionを使用して、これら2つの更新を組み合わせるにはどうすればよいですか?
Microsoft SQL Server ManagementStudioの使用
そのためにUINION
は必要ありません-内部結合を外部結合のペアに置き換えると、次のようになります。
UPDATE c
SET c.order_status = 1
FROM Customer AS c
LEFT OUTER JOIN Order_Web As ow ON c.id = ow.customer_id
LEFT OUTER JOIN Order As o ON c.id = o.customer_id
WHERE ow.order_filled = 1 OR o.order_filled = 1
次のように、WHERE EXISTS
を使用することもできます。
UPDATE c
SET c.order_status = 1
FROM Customer AS c
WHERE EXISTS (
SELECT 1 FROM Order_Web As ow WHERE c.id = ow.customer_id AND ow.order_filled = 1
) OR EXISTS (
SELECT 1 FROM Order As o WHERE c.id = o.customer_id AND o.order_filled = 1
)
UNION
を使用する必要がある場合は、次のように実行できます。
UPDATE c
SET c.order_status = 1
FROM Customer AS c
WHERE c.id in (
SELECT ow.id FROM Order_Web As ow WHERE ow.order_filled = 1
UNION
SELECT o.id FROM Order As o WHERE o.order_filled = 1
)
またはJOIN
を持つ同じもの:
UPDATE c
SET c.order_status = 1
FROM Customer AS c
JOIN (
SELECT ow.id AS id FROM Order_Web As ow WHERE ow.order_filled = 1
UNION
SELECT o.id AS id FROM Order As o WHERE o.order_filled = 1
) AS ids ON ids.id = c.id
UPDATE c
SET c.order_status = 1
FROM (
SELECT customer_id
FROM order_web
WHERE order_filled = 1
UNION
SELECT customer_id
FROM order
WHERE order_filled = 1
) o
JOIN customer c
ON c.id = o.customer_id
ユニオンクエリをサブクエリに入れることができます。
update customer
c.order_status = 1
where id in
(union query goes here)