admin

如何限制MySQL中变量的增量

sql

这是我的桌子。

+----+--------+---------+------------+
| id | idName | fldName | fld_Date   |
+----+--------+---------+------------+
|  1 |      1 | Marlon  | 2013-06-03 |
|  2 |      1 | Marlon  | 2013-06-05 |
|  3 |      1 | Marlon  | 2013-06-07 |
|  4 |      1 | Marlon  | 2013-06-08 |
|  5 |      1 | Marlon  | 2013-06-11 |
|  6 |      2 | Dawn    | 2013-06-03 |
|  7 |      2 | Dawn    | 2013-06-06 |
|  8 |      2 | Dawn    | 2013-06-08 |
|  9 |      2 | Dawn    | 2013-06-11 |
| 10 |      2 | Dawn    | 2013-06-15 |
| 11 |      3 | Jenny   | 2013-06-15 |
| 12 |      3 | Jenny   | 2013-06-19 |
| 13 |      3 | Jenny   | 2013-06-14 |
| 14 |      3 | Jenny   | 2013-06-21 |
+----+--------+---------+------------+

输出应该是这样的

+----+--------+---------+----+------------+------------+
| id | idName | fldName | i  | fld_Date   | next_date  |
+----+--------+---------+----+------------+------------+
|  1 |      1 | Marlon  |  1 | 2013-06-03 | 2013-06-05 |
|  2 |      1 | Marlon  |  2 | 2013-06-05 | 2013-06-07 |
|  3 |      1 | Marlon  |  3 | 2013-06-07 | 2013-06-08 |
|  4 |      1 | Marlon  |  4 | 2013-06-08 | 2013-06-11 |
|  5 |      1 | Marlon  |  5 | 2013-06-11 | 0          |
|  6 |      2 | Dawn    |  1 | 2013-06-03 | 2013-06-06 |
|  7 |      2 | Dawn    |  2 | 2013-06-06 | 2013-06-08 |
|  8 |      2 | Dawn    |  3 | 2013-06-08 | 2013-06-11 |
|  9 |      2 | Dawn    |  4 | 2013-06-11 | 2013-06-15 |
| 10 |      2 | Dawn    |  5 | 2013-06-15 | 0          |
| 11 |      3 | Jenny   |  1 | 2013-06-15 | 2013-06-19 |
| 12 |      3 | Jenny   |  2 | 2013-06-19 | 2013-06-14 |
| 13 |      3 | Jenny   |  3 | 2013-06-14 | 2013-06-21 |
| 14 |      3 | Jenny   |  4 | 2013-06-21 | 0          |
+----+--------+---------+----+------------+------------+

这是我的代码…

SELECT id,idName,fldName, @i := @i + 1 i, fld_Date, next_date 
FROM ( SELECT id,idName,fldName, @d next_date, @d := fld_Date fld_Date 
       FROM x_table, 
      (SELECT @d := 0) d ORDER BY id DESC) q, 
      (SELECT @i := 0) n ORDER BY id;

我很难根据不同的数量来限制增量idName…您能帮我这些吗....


阅读 75

收藏
2021-06-07

共1个答案

admin

试试这个:

SELECT id, idname, fldname, IF(@idname=(@idname:=idname), @id:=@id+1, @id:=1) i, fld_Date, next_Date
FROM (SELECT a.id, a.idName, a.fldName, a.fld_Date, IFNULL(b.fld_Date, 0) next_Date
        FROM x_table a 
        LEFT JOIN x_table b ON a.idname = b.idname AND a.fld_Date < b.fld_Date
        GROUP BY a.id) A, (SELECT @id:=0, @idname:=0) B

检查 FIDDLE 上的查询
****

输出

| ID | IDNAME | FLDNAME | I |                    FLD_DATE |  NEXT_DATE |
------------------------------------------------------------------------
|  1 |      1 |  Marlon | 1 | June, 03 2013 00:00:00+0000 | 2013-06-05 |
|  2 |      1 |  Marlon | 2 | June, 05 2013 00:00:00+0000 | 2013-06-07 |
|  3 |      1 |  Marlon | 3 | June, 07 2013 00:00:00+0000 | 2013-06-08 |
|  4 |      1 |  Marlon | 4 | June, 08 2013 00:00:00+0000 | 2013-06-11 |
|  5 |      1 |  Marlon | 5 | June, 11 2013 00:00:00+0000 |          0 |
|  6 |      2 |    Dawn | 1 | June, 03 2013 00:00:00+0000 | 2013-06-06 |
|  7 |      2 |    Dawn | 2 | June, 06 2013 00:00:00+0000 | 2013-06-08 |
|  8 |      2 |    Dawn | 3 | June, 08 2013 00:00:00+0000 | 2013-06-11 |
|  9 |      2 |    Dawn | 4 | June, 11 2013 00:00:00+0000 | 2013-06-15 |
| 10 |      2 |    Dawn | 5 | June, 15 2013 00:00:00+0000 |          0 |
| 11 |      3 |   Jenny | 1 | June, 15 2013 00:00:00+0000 | 2013-06-19 |
| 12 |      3 |   Jenny | 2 | June, 19 2013 00:00:00+0000 | 2013-06-21 |
| 13 |      3 |   Jenny | 3 | June, 14 2013 00:00:00+0000 | 2013-06-15 |
| 14 |      3 |   Jenny | 4 | June, 21 2013 00:00:00+0000 |          0 |
2021-06-07