Duplicate (repeat) rows in sql query result

问题

Let's say I have a table with two rows

 id | value |
----+-------+
 1  |   2   |
 2  |   3   |

I want to write a query that will duplicate (repeat) each row based on the value.
I want this result (5 rows total):

 id | value |
----+-------+
 1  |   2   |
 1  |   2   |
 2  |   3   |
 2  |   3   |
 2  |   3   |

I'm using PostgreSQL 9.4.

回答1:

You can use generate_series():

select t.id, t.value
from (select t.id, t.value, generate_series(1, t.value)
      from t 
     ) t;

You can do the same thing with a lateral join:

select t.id, t.value
from t, lateral
     generate_series(1, t.value);

来源：https://stackoverflow.com/questions/35293084/duplicate-repeat-rows-in-sql-query-result