mysql - 将记录从一个表移动到另一个表插入 X 次

Question

我有一个类似这样的表:

id
name
datetime
quantity

我想用 SQL 将这些记录从一个表移动到另一个没有数量列的表，插入记录 X 次，其中 X 是数量的值，所以 ....

id name       datetime    quantity
----------------------------------
5  book-order 15-Mar-2010 3

# becomes

id name       datetime  
------------------------
5  book-order 15-Mar-2010
6  book-order 15-Mar-2010
7  book-order 15-Mar-2010

有没有办法在纯 SQL 中执行此操作？

Answer 1

这里有一种方法，假设数量不超过 100:

insert into t2(name, datetime)
    select name, datetime
    from t1 join
         (select d1*10+d2 as num
          from (select 0 as n union all select 1 union all select 2 union all select 3 union all select 4 union all
                select 5 union all select 6 union all select 7 union all select 8 union all select 9
               ) d1 cross join
               (select 0 as n union all select 1 union all select 2 union all select 3 union all select 4 union all
                select 5 union all select 6 union all select 7 union all select 8 union all select 9
              ) d2
         ) nums
         on nums.num < t1.qty

如果数量太大，困难的部分是生成一个数字表。