Question

我的表

教室

id  class   no_of_seats start_seat_no   end_seat_no
1   A1      3           105             107
2   A2      2           108             109
3   A3      2           110             111

我想在表格中插入数据的 seat_records 像这样

id  class   seat_no
1   A1      105
2   A1      106
3   A1      107
4   A2      108
5   A2      109
6   A3      110
7   A3      111
8   A3      112

尝试做以前问题中给出的所有内容，但失败了。

SELECT 'A1' class, 105 start_seat_no, 107 end_seat_no
    UNION ALL
    SELECT 'A2',108,109
From classRoom

Answer 1

您需要一个整数来源才能进行连接。如果您有足够的行，则可以使用相同的表和变量：

insert into seat_records(class, seat_no)
    select class, cr.start_seat_no + n.n - 1
    from ClassRoom cr join
         (select @rn := @rn + 1 as n
          from ClassRoom cross join
               (select @rn := 0) vars
         ) n
         on cr.start_seat_no + n.n - 1 <= cr.end_seat_no;

您应该将id本身添加为自动递增列。这样，它将在输入时设置。如果你真的想在输入上设置它，你也可以使用变量：

insert into seat_records(id, class, seat_no)
    select @id := @id + 1, class, cr.start_seat_no + n.n - 1
    from ClassRoom cr join
         (select @rn := @rn + 1 as n
          from ClassRoom cross join
               (select @rn := 0) vars
         ) n
         on cr.start_seat_no + n.n - 1 <= cr.end_seat_no cross join
         (select @id := 0) vars

MYSQL从范围生成连续数字

1 个答案: