mysql 根据 select 从一个 table 插入到另一个

Question

假设我们有

Table一个

field 1 | field 2

orange  | fruit
apple   | fruit

和

Table B

field 1 | field 2

orange  | fruit
lemon   | fruit

并且只想插入从 Table B 到 Table A 的在字段 1 上不匹配的行，以便 Table A 变为：

Table一个

field1  | field2

orange  | fruit
apple   | fruit
lemon   | fruit

我试过了

insert into tableA (field1, field2)
select field1, field2 from tableB
where not exists 
(select * from tableA as a join tableB as b on a.field1 = b.field1)

（无插入）

和

insert into tableA (field1, field2)
select field1, field2  from tableA as a left join tableB as b on a.field1 = b.field1  
union 
select field1, field2  from tableA as s right join tableB as b on a.field1 = b.field1 
where a.field1 != b.field1

（插入错误）

Answer 1

您的 NOT EXISTS 表达式不太正确，它需要查看您尝试插入的 tableB 中的值：

INSERT INTO tableA (field1, field2)
SELECT field1, field2 
FROM tableB b
WHERE NOT EXISTS (SELECT * FROM tableA a WHERE a.field1 = b.field1)

此查询后 SELECT * FROM tableA 的输出：

field1  field2
orange  fruit
apple   fruit
lemon   fruit

Demo on db-fiddle

Answer 2

你可以简单地使用 union 或使用下面的代码

INSERT INTO Table A SELECT * FROM Table B
WHERE NOT EXISTS (SELECT 1 FROM TABLE A Data
                  WHERE A.field1 = Data.field1 AND 
                  A.field2 = Data.field2)

Answer 3

这可能不是最好的解决方案，但这个使用连接的解决方案对我有用：

INSERT INTO A(F1,F2)
SELECT * 
FROM A NATURAL RIGHT JOIN B AS TAB
WHERE TAB.F1 NOT IN (
SELECT F1
FROM A NATURAL JOIN B
);

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