mysql，使用select子查询插入

我有很多产品在

产品类别

表中，其

类别id

为5。 我添加了一个新的

category\u id

19。 如何将类别5中的所有产品也添加到类别19中

我正在尝试这样做：

insert into product_categories( category_id, product_id )
select 19,
   (select product_id
    from product_categories
    where category_id = 5)

INSERT INTO product_categories( category_id, product_id )
SELECT 19, product_id FROM product_categories WHERE category_id =5

INSERT INTO table_a (field, field, timestamp) 
 VALUES (
     (SELECT id FROM tablex WHERE id = :xid LIMIT 1),
     (SELECT id FROM tabley WHERE id = :yid LIMIT 1),
     NOW()
 )

但是我得到了一个

子查询，它返回了超过1行的错误。
试试这个：

INSERT INTO product_categories (category_id, product_id)
  SELECT 19 AS category_id, product_id 
  FROM product_categories 
  WHERE category_id =5;

试着这样做：

insert into product_categories( category_id, product_id )
select 19,
   (select product_id
    from product_categories
    where category_id = 5)

INSERT INTO product_categories( category_id, product_id )
SELECT 19, product_id FROM product_categories WHERE category_id =5

INSERT INTO table_a (field, field, timestamp) 
 VALUES (
     (SELECT id FROM tablex WHERE id = :xid LIMIT 1),
     (SELECT id FROM tabley WHERE id = :yid LIMIT 1),
     NOW()
 )

有限度地尝试

INSERT INTO product_categories( category_id, product_id ) SELECT 19 , (

SELECT product_id FROM product_categories WHERE category_id =5 LIMIT 1)

您可以这样做：

insert into product_categories( category_id, product_id )
select 19,
   (select product_id
    from product_categories
    where category_id = 5)

INSERT INTO product_categories( category_id, product_id )
SELECT 19, product_id FROM product_categories WHERE category_id =5

INSERT INTO table_a (field, field, timestamp) 
 VALUES (
     (SELECT id FROM tablex WHERE id = :xid LIMIT 1),
     (SELECT id FROM tabley WHERE id = :yid LIMIT 1),
     NOW()
 )

一点也不需要，只要记住接受你所有问题的正确答案，这样，如果其他人有相同的问题，他们会更容易找到解决方案。你不应该真的需要限制，但如果你没有使用唯一的行id，那么就方便了