在 MySQL 中生成特定数量的行（不使用 table）

Question

如何使用 SQL 查询生成定义数量的行——而不使用 table（这些行已经存在）？

例如，为了 return 3 行，我们可以这样做：

select * from (
    select 1 union all
    select 1 union all
    select 1
) t

结果如下：


1
1
1

但是，如果我需要 return，比方说，一千行，这是不切实际的。还有别的办法吗？

Answer 1

您可以使用：

WITH recursive numbers AS 
(  select 1 as Numbers
   union all
   select Numbers
   from numbers
   limit 1000
 )
select * from numbers;

根据需要更改限制。

另一种选择是：

WITH recursive numbers AS 
(  select 1 as Numbers
   union all
   select Numbers + 1
   from numbers
   where Numbers < 1000
 )
select * from numbers;

您可能需要将@@cte_max_recursion_depth增加到一个更大的值。

测试于

mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.25    |
+-----------+
1 row in set (0.00 sec)


mysql>     WITH recursive numbers AS
    ->     (  select 1 as Numbers
    ->        union all
    ->        select Numbers
    ->        from numbers
    ->        limit 100
    ->      )
    ->     select * from numbers;
+---------+
| Numbers |
+---------+
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
|    1 |
+------+
100 rows in set (0.00 sec)

在 MySQL 中生成特定数量的行（不使用 table）

Generate a specific number of rows in MySQL (without using a table)

mysql

sql

select

rows

data-generation