SQL数据库视图关联

基础知识

Left join 左连接
As 添加别名
On 连接条件 条件要对应

CREATE VIEW 视图 AS
查询语句
GO

SQL语句

select a.MaterialName,a.MaterialNo,b.Count from TB_MaterialInfo as a
left join TB_InventoryDetails as b
on a.MaterialNo=b.MaterialNo

TB_MaterialInfo as a 的意思是TB_MaterialInfo 的别名是a
TB_InventoryDetails as b的意思是TB_InventoryDetails 的别名是b

SQL语句的意思是 通过左连接a表里的MaterialNo与b表里的MaterialNo字段 查找a表里的MaterialName，MaterialNo
b表里的Count 字段

```sql
SELECT
 a.*, b.BOMNo,
 ISNULL(b.MVersion,'') AS MVersion,
 ISNULL(b.Version,'') AS Version,
 ISNULL(b.ValidityDate,'') AS ValidityDate,
 ISNULL(b.Status,'') AS Status,
 ISNULL(c.MaterialName,'') AS MaterialName
FROM
 TB_MaterialHangingDetail a
LEFT JOIN TB_MaterialHanging b ON a.MaterialHangingNo = b.MaterialHangingNo
LEFT JOIN TB_MaterialInfo c ON a.MaterialNo = c.MaterialNo

关联3个表
isnull方法   当该字段为null时将null变为‘’