一、当用一个表中的数据来更新另一个表中的数据,T-SQL提供多种写法(下面列出了二种),但建议用第一种写法,虽然传统,但结构清晰。
并且要注意,当用一个表中的数据来更新另一个表中的数据时,二个表一定要有关联!
1.
update t1
where t1.c1 = t2.c1
2.
Update t1
from t1 inner join t2
示例:
UPDATE temp_Org_employee
SET temp_Org_employee.mobile = c.tele
FROM temp_Org_employee e
INNER JOIN
(SELECT a.name, b.ID, a.tele, b.mobile
FROM EmplTeleTb a
LEFT JOIN
(SELECT *
FROM temp_Org_employee
WHERE DepartmentId IN
(SELECT ID
FROM org_Department
WHERE CompanyID =
'T200812051418466710000194')) b
ON a.Name = b.EmplName
WHERE a.tele <> b.mobile) c
ON e.ID = c.ID
示例2:
UPDATE temp_Org_employee
SET temp_Org_employee.mobile = c.tele
FROM (SELECT a.name, b.ID, a.tele, b.mobile
FROM EmplTeleTb a
LEFT JOIN
(SELECT *
FROM temp_Org_employee
WHERE DepartmentId IN
(SELECT ID
FROM org_Department
WHERE CompanyID = 'T200812051418466710000194'))
b
ON a.Name = b.EmplName
WHERE a.tele <> b.mobile) c
WHERE temp_Org_employee.ID = c.ID
示例3:
UPDATE temp_Org_employee
SET mobile = c.tele
FROM temp_Org_employee e,(SELECT a.name, b.ID, a.tele, b.mobile
FROM EmplTeleTb a
LEFT JOIN
(SELECT *
FROM temp_Org_employee
WHERE DepartmentId IN
(SELECT ID
FROM org_Department
WHERE CompanyID = 'T200812051418466710000194'))
b
ON a.Name = b.EmplName
WHERE a.tele <> b.mobile) c
WHERE e.ID = c.ID
二、FROM 子句中指定的表的别名不能作为 SET column_name 子句中被修改字段的限定符使用。
SET e.mobile = c.tele
FROM temp_Org_employee e,(SELECT a.name, b.ID, a.tele, b.mobile
FROM EmplTeleTb a
LEFT JOIN
(SELECT *
FROM temp_Org_employee
WHERE DepartmentId IN
(SELECT ID
FROM org_Department
WHERE CompanyID = 'T200812051418466710000194'))
b
ON a.Name = b.EmplName
WHERE a.tele <> b.mobile) c
WHERE e.ID = c.ID