Question

我有一张表需要复制行。该表是有一个主要的自动递增键以及用于将行组合在一起的列。是否有一种方法可以复制组ID设置为从最后一个值增加的一系列行？

这是基本示例原始表数据

pri | grp
----------
1   | 1
2   | 9
3   | 2
4   | 1
5   | 2
6   | 9
7   | 2
- copied -
8   | 10
9   | 12
10  | 11
11  | 10
12  | 11
13  | 12
14  | 11

我的目标是复制第1-7行并得到如下结果：

SET @new = (SELECT MAX(grp)+1 FROM tbl), @prev = (SELECT MIN(grp) FROM tbl);
INSERT INTO tbl (grp) (
SELECT IF(grp=@prev,
   -- set @prev, use @new
   , CASE
      WHEN (@prev:=grp) IS NULL THEN NULL
      ELSE @new
     END
   -- set @prev, update and use @new
   , CASE
      WHEN (@prev:=grp) IS NULL THEN NULL
      ELSE @new:=@new+1
     END)
FROM tbl
ORDER BY grp
)

请注意，复制行的grp在原始Max grp之后开始，然后为每个新grp递增1。

pri | grp
----------
1   | 1
2   | 9
3   | 2
4   | 1
5   | 2
6   | 9
7   | 2
- copied -
8   | 10
9   | 14
10  | 11
11  | 10
12  | 12
13  | 15
14  | 13

这给了我以下结果，看起来@prev变量没有正确更新。

while((fscanf(inputFile1, "%d", &temp1) == 1) && (fscanf(inputFile2, "%d", &temp2) == 1))
{
  printf("temp1: %d\n", temp1);
  printf("temp2: %d\n", temp2);

  if (temp1 > temp2)
  {
     fprintf(outputFile, "%d\n", temp2);
     fprintf(outputFile, "%d\n", temp1);
  }
  else if (temp1 < temp2)
  {
     fprintf(outputFile, "%d\n", temp1);
     fprintf(outputFile, "%d\n", temp2);
  }
  else if (temp1 == temp2)
  {
     fprintf(outputFile, "%d\n", temp1);
     fprintf(outputFile, "%d\n", temp2);
  }
}

File 1    File 2
5         1
10        43
30        55
50        98
345       500

Output
1
5
10
43
30
55
50
98
345 
500

Answer 1

我认为您需要在子查询中分配新的grp，然后按顺序排序

DROP TABLE IF EXISTS Tbl;
CREATE TABLE Tbl (PRI INT AUTO_INCREMENT PRIMARY KEY, GRP INT);
INSERT INTO Tbl (pri,grp) VALUES
(1   , 1),
(2   , 9),
(3   , 2),
(4   , 1),
(5   , 2),
(6   , 9),
(7   , 2);


INSERT INTO Tbl (grp) 
select  s.n
from
(
SELECT  t.pri tpri,t.grp tgrp
         ,if(t.grp <> @prev,@new:=@new+1,@new) n
         ,@prev:=t.grp p
FROM tbl t,(SELECT @new:= (select max(grp) from tbl),@prev:=0) n
order by t.grp
) s 
order by s.tpri
;

MariaDB [sandbox]> select * from tbl;
+-----+------+
| PRI | GRP  |
+-----+------+
|   1 |    1 |
|   2 |    9 |
|   3 |    2 |
|   4 |    1 |
|   5 |    2 |
|   6 |    9 |
|   7 |    2 |
|   8 |   10 |
|   9 |   12 |
|  10 |   11 |
|  11 |   10 |
|  12 |   11 |
|  13 |   12 |
|  14 |   11 |
+-----+------+
14 rows in set (0.00 sec)

复制行和增量列

1 个答案: