Sql server MSSQL：如何从不同的表中删除重复的列值？

如何从不同的表中删除重复的列值？
给出了不带外键引用的下表：

表A

Id IdentifierString
-------------------
1  String A
2  String B
3  String C

Id IdentifierString
-------------------
1  NULL
2  String B
3  NULL

表B

Id IdentifierString
-------------------
1  String A
2  String C
3  String D

Id IdentifierString
-------------------
1  NULL
2  NULL
3  String D

我要删除所有重复的列值：

表A

Id IdentifierString
-------------------
1  String A
2  String B
3  String C

Id IdentifierString
-------------------
1  NULL
2  String B
3  NULL

表B

Id IdentifierString
-------------------
1  String A
2  String C
3  String D

Id IdentifierString
-------------------
1  NULL
2  NULL
3  String D

---

这是如何做到的？

这可以通过使用

UNION ALL

、

have（COUNT）

和

UPDATE

语句来实现，如下所示：

CREATE TABLE Table1 (Id INT, IdentifierString VARCHAR (20));

INSERT INTO Table1 (Id, IdentifierString) VALUES
(1, 'String A'),
(2, 'String B'),
(3, 'String C');

CREATE TABLE Table2 (Id INT, IdentifierString VARCHAR (20));

INSERT INTO Table2 (Id, IdentifierString) VALUES
(1, 'String A'),
(2, 'String C'),
(3, 'String D');

DECLARE @DuplicateEntries TABLE (IdentifierString VARCHAR(20));

INSERT INTO @DuplicateEntries (IdentifierString)
SELECT IdentifierString FROM (
    SELECT IdentifierString FROM Table1
    UNION ALL
    SELECT IdentifierString FROM Table2
) A 
GROUP BY IdentifierString
HAVING COUNT(IdentifierString) > 1;

UPDATE T1
SET T1.IdentifierString = NULL
FROM Table1 T1
JOIN @DuplicateEntries D ON D.IdentifierString = T1.IdentifierString;

UPDATE T2
SET T2.IdentifierString = NULL
FROM Table2 T2
JOIN @DuplicateEntries D ON D.IdentifierString = T2.IdentifierString;

SELECT * FROM Table1;
SELECT * FROM Table2;

---

请在

上找到正在运行的演示，这是您删除重复项的dml脚本

delete from table1 where id in (select id from (
    select id, t1.IdentifierString, t2.IdentifierStringfrom table1 t1
    left join table2 t2 on t2.IdentifierString= t1.IdentifierString) as t3
where isnull(t1.IdentifierString, '') = '' or  isnull(t2.IdentifierString, '') = '')

delete from table2 where id in (select id from (
    select id, t1.IdentifierString, t2.IdentifierStringfrom table2 t1
    left join table1 t2 on t2.IdentifierString= t1.IdentifierString) as t3
where isnull(t1.IdentifierString, '') = '' or  isnull(t2.IdentifierString, '') = '')

---

抱歉，我想再问一个问题，但不幸的是我做了一次编辑，啊…@Powerslave不客气。我很高兴能帮上忙！