将行从一个表插入到另一个表，在 SQL Server 上具有相同的架构和复合键

I need to insert rows into table b from table a, where an identical key does not already exists in table b.

我该怎么做?

推荐答案

-- Set up sample data
CREATE TABLE A(Key1 int NOT NULL, Key2 nvarchar(10) NOT NULL, Data nvarchar(20))
INSERT INTO A(Key1, Key2, Data) Values(10, 'AA', 'My first value')
SELECT * INTO B FROM A
INSERT INTO A(Key1, Key2, Data) Values(20, 'BA', 'My second value')

-- Copy the missing rows from table A to table B
INSERT INTO B(Key1, Key2, Data)
SELECT A.Key1, A.Key2, A.Data
FROM A
LEFT JOIN B ON A.Key1 = B.Key1 AND A.Key2 = B.Key2
WHERE B.Key1 IS NULL