sqlserver 基于一张表更新另外一张表

SQL Server中如何基于一个表的数据更新另一个表的对应数据？实现的SQL语句有很多方式：

方式一 INNER JOIN

UPDATE
    Table_A
SET
    Table_A.col1 = Table_B.col1,
    Table_A.col2 = Table_B.col2
FROM
    Some_Table AS Table_A
    INNER JOIN Other_Table AS Table_B
        ON Table_A.id = Table_B.id
WHERE
    Table_A.col3 = ‘cool‘

方式二使用MERGE关键字

MERGE INTO YourTable T
   USING other_table S
      ON T.id = S.id
         AND S.tsql = ‘cool‘
WHEN MATCHED THEN
   UPDATE
      SET col1 = S.col1,
          col2 = S.col2;

或者

MERGE INTO YourTable T
   USING (
          SELECT id, col1, col2
            FROM other_table
           WHERE tsql = ‘cool‘
         ) S
      ON T.id = S.id
WHEN MATCHED THEN
   UPDATE
      SET col1 = S.col1,
          col2 = S.col2;

注： SQL Server 2008 或者以上版本才支持MERGE关键字

方式三使用CTE

;WITH CTE
     AS (SELECT T1.Col1,
                T2.Col1 AS _Col1,
                T1.Col2,
                T2.Col2 AS _Col2
         FROM   T1
                JOIN T2
                  ON T1.id = T2.id
         /*Where clause added to exclude rows that are the same in both tables
           Handles NULL values correctly*/
         WHERE EXISTS(SELECT T1.Col1,
                             T1.Col2
                       EXCEPT
                       SELECT T2.Col1,
                              T2.Col2))
UPDATE CTE
SET    Col1 = _Col1,
       Col2 = _Col2

方式四使用EXISTS

UPDATE suppliers
SET supplier_name = (SELECT customers.name
                     FROM customers
                     WHERE customers.customer_id = suppliers.supplier_id)
WHERE EXISTS (SELECT customers.name
              FROM customers
              WHERE customers.customer_id = suppliers.supplier_id);

此外介绍下 SQL Server 2008 Merge into用法

只有 sqlserver 2008以上版本才有meger关键字

--创建测试表
CREATE TABLE t_A
(MCLASS VARCHAR(20),SNO VARCHAR(20))
INSERT INTO t_A
SELECT ‘L-1‘,‘123‘
UNION ALL
SELECT ‘L-2‘,‘234‘
UNION ALL
SELECT ‘L-3‘,‘345‘

CREATE TABLE t_B
(MCLASS VARCHAR(20),SNO VARCHAR(20))
INSERT INTO t_B
SELECT ‘L-1‘,‘999‘
UNION ALL
SELECT ‘L-2‘,‘999‘
UNION ALL
SELECT ‘L-4‘,‘888‘

--确定目标表
merge into t_A as a
--从t_B表中查找MCLASS相同的数据
using t_B as b on a.MCLASS=b.MCLASS
--当MCLASS相同时，则更新t_A中SNO字段
when Matched then update set a.SNO=b.SNO
--当t_A表中不存在MCLASS相同的数据时，则从t_B表插入目标表t_A
when Not Matched then Insert(MCLASS,SNO) values(b.MCLASS,b.SNO);

select * from t_A
select * from t_B

drop table t_A
drop table t_B
t_a

MCLASS SNO

-------------------- --------------------
L-1                  123
L-2                  234
L-3                  345

(3 行受影响)
t_b
MCLASS               SNO
-------------------- --------------------
L-1                  999
L-2                  999
L-4                  888

(3 行受影响)

----------------------------------------------------------------------

更新后的t_a

MCLASS               SNO
-------------------- --------------------
L-1                  999
L-2                  999
L-3                  345
L-4                  888

(4 行受影响)

Merge语句可以将一个表中的数据合并到另一个表中，在合并的同时可以进行插入、删除、更新等操作。

原文链接：https://blog.csdn.net/yole_grise/article/details/15337973