Question

我有两个表：

用户：user_id(PK) | name
产品：product_id(PK) | product | user_id(FK)

这是一对多关系（一个用户可以拥有多个产品）。我用以下语句创建了表：

String stmt_user = "create table user (user_id int not null generated by default as identity," 
                   + "name varchar(20), " 
                   + "primary key(user_id))";

String stmt_prod = "create table product (product_id int not null generated by default as identity,"
                   + "product varchar(20), "
                   + "constraint ads_pk primary key(product_id), "
                   + "foreign key(user_id)  references user(user_id) on delete cascade)";

当我想将多个产品插入ID为2的一个特定用户时该怎么办？
像这样：“在用户（用户ID）= 2的地方插入产品值（产品）”。
这是我的桌子的样子：

|---------------------|------------------|---------------|
|      product_id     |     user_id      |    product    |
|---------------------|------------------|---------------|
|          1          |         2        |     bacon     |
|---------------------|------------------|---------------|
|          2          |         2        |     pizza     |
|---------------------|------------------|---------------|
|          3          |         2        |     beans     |
|---------------------|------------------|---------------|

Answer 1

啊终于从这里找到了我的答案： Insert into table with a foreign key

我必须更新我的创建产品声明：

String stmt_prod = "create table product (product_id int not null generated by default as identity,"
                   + "product varchar(20), "
                   + "constraint ads_pk"
                   + "foreign key(user_id) references user(user_id) on delete cascade)";

现在我的插入产品声明如下所示：

"insert into product (product, user_id) select product, u.user_id from user u where u.user_id = 2");

如何使用外键将数据插入表中？

1 个答案: