我需要每个订单的行项目数。
在此示例中,订单 10 有 0,订单 11 有 2 行。
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'dbo.OrderDetail') AND type in (N'U'))
DROP TABLE OrderDetail
IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'dbo.OrderHeader') AND type in (N'U'))
DROP Table OrderHeader
GO
CREATE TABLE OrderHeader(
OrderHeaderID Int Primary Key Identity(10,1),
CustID Int)
GO
CREATE TABLE OrderDetail(
OrderDetailID Int Primary Key Identity(100,1),
OrderHeaderID Int REFERENCES OrderHeader,
ItemID Int)
GO
DECLARE @OrderHeaderID Int
INSERT INTO OrderHeader(CustID) VALUES(1000)
INSERT INTO OrderHeader(CustID) VALUES(1001)
SET @OrderHeaderID=SCOPE_IDENTITY()
INSERT INTO OrderDetail(OrderHeaderID,ItemID) VALUES(@OrderHeaderID,3)
INSERT INTO OrderDetail(OrderHeaderID,ItemID) VALUES(@OrderHeaderID,4)
GO
SELECT
OrderDetailID,ItemID,OrderHeader.OrderHeaderID,CustID
FROM OrderDetail
JOIN OrderHeader
ON OrderDetail.OrderHeaderID=OrderHeader.OrderHeaderID
--
这是我需要帮助的地方 我需要 COUNT(*)
FROM OrderDetail WHERE OrderDetail.OrderHeaderID=OrderHeader.OrderHeaderID
SELECT OrderHeader.OrderHeaderID,CustID,CountOfOrderDetail
FROM OrderHeader
JOIN OrderDetail
ON OrderDetail.OrderHeaderID=OrderHeader.OrderHeaderID