如何在表之间传输数据，仅在id不存在的情况下

Question

我需要从表A复制一组数据到表B，像这样：

INSERT INTO TableB(id,field1,field2) 
SELECT id,field1,field2 FROM TableA

上面的内容可以很好地工作，但是 TableB 可能已经包含一些我需要复制的记录，由 PK id 标识。

因此，如果 id 值不在表 B 中，我如何才能向 添加一个子句，仅 插入一条记录？我知道可以在 INSERT 语句的末尾添加一个 WHERE 子句，但我不确定如何将它应用于每条记录。

Answer 1

您可以使用左连接，如下所示

INSERT INTO TableB(id,field1,field2) 
SELECT id,field1,field2 FROM TableA 
left join TableB on TableB.id = TableA.id
where TableB.id is null

Answer 2

您可能需要一个带有 exists() 的 where 子句

INSERT INTO TableB(id,field1,field2) 
SELECT id,field1,field2 FROM TableA a
WHERE  not exists (SELECT 1 FROM TableB b WHERE a.id = b.id)

Answer 3

INSERT INTO TableB(id,field1,field2)     
SELECT A.id,A.field1,A.field2 FROM TableA WHERE NOT EXISTS
    (SELECT B.ID FROM TABLEB WHERE B.ID = A.ID)

Answer 4

尝试使用左连接：

INSERT INTO TableB(id,field1,field2) 
SELECT id,field1,field2 FROM TableA left join TableB on tableA.id = tableb.id where tablea.id is null

Answer 5

你可以看看比较 NOT IN vs. NOT EXISTS vs. LEFT JOIN / IS NULL.

的 3 种方法

The best way to search for missing values in MySQL is using a LEFT JOIN / IS NULL or NOT IN rather than NOT EXISTS.

您可以使用 NOT EXISTS.

INSERT INTO TableB (id, field1, field2) 
SELECT id, field1, field2 
FROM TableA t1
WHERE NOT EXISTS (
                   SELECT *
                   FROM TableB t2
                   WHERE t1.id = t2.id
                  )

您也可以使用 LEFT JOIN.

INSERT INTO TableB (id, field1, field2) 
SELECT id, field1, field2 
FROM TableA t1
LEFT JOIN TableB t2 ON t1.id = t2.id
WHERE t2.id IS NULL

您也可以使用 NOT IN.

INSERT INTO TableB (id, field1, field2) 
SELECT id, field1, field2 
FROM TableA t1
WHERE t1.id NOT IN (
                    SELECT t2.id 
                    FROM TableB t2 
                    WHERE t1.id = t2.id
                   )

Answer 6

最好使用 set operator EXCEPT 以获得最佳性能，如下所示：

此处将取两组数据进行减法运算并给出输出

INSERT INTO TableB(id,field1,field2) (
SELECT id,field1,field2 FROM TableA 
 except
SELECT id,field1,field2 FROM TableB )

Answer 7

INSERT INTO TableB(id,field1,field2) SELECT T2.id,T2.field1,T2.field2 FROM TableA as T1 在 T1.id <> T2.id

上作为 T2 内部加入 TableB

如何在表之间传输数据，仅在id不存在的情况下

How to transfer data between tables, only where id does not exist

mysql

sql

database

database-design