Question

在下面的sql中，我试图根据perCent列增加排名。这里的事情是，当找到类似的分数时，等级应保持不变。

select id, perCent, 
       @curRank := if( parent = @prevParent and perCent != @prevPerCent , @curRank + 1, 1) AS rank,

       @prevParent := parent, @prevPerCent := perCent
from (
    select child.id, child.perCent, child.parent
    from likesd parent
    join likesd child
       on parent.id = child.parent
    where parent.type = 3
    order by parent.id, child.perCent desc) x
cross join (SELECT @curRank := 0, @prevParent := null, @prevPerCent := null) r

例如：50是等级1,30是等级2,30再次等级2,20是等级3.想法是在找到类似等级时不增加。

我该怎么做？如何在if语句中告诉MySql不要增加它？

基本逻辑是

if parent = @prevParent, if perCent = @prevPerCent
// Dont increment
else
increment

我在MySql中遇到了这个部分。你能帮忙吗？

主要表

"id"    "type"  "parent"    "country"   "votes" "perCent"
"24"    "1"     "1"         "US"        "35"    "0"
"25"    "3"     "24"        "US"        "35"    "0"
"26"    "10"    "25"        "US"        "15"    "50.00"
"27"    "10"    "25"        "US"        "10"    "33.33"
"28"    "10"    "25"        "US"        "10"    "33.33"

"29"    "1"     "1"         "US"        "50"    "0"
"30"    "3"     "29"        "US"        "50"    "0"
"31"    "10"    "30"        "US"        "20"    "40.00"
"32"    "10"    "30"        "US"        "15"    "25.00"
"33"    "10"    "30"        "US"        "15"    "35.00"

预期结果：

"id"    "perCent" "rank"
"26"    "50.00"   "1"
"27"    "33.33"   "2" 
"28"    "33.33"   "2" // No increment in rank if the perCent is same as above

"31"    "40.00"    "1" // Continious incrementing here. PerCents differ.
"33"    "35.00"    "2"
"32"    "25.00"    "3"

一些不起作用的努力（呃！我放弃了）

select id, perCent, 
      @curRank := if(parent = @prevParent, TRUE, FALSE) AS rank,

      @curCent := if(perCent = @prevCent, FALSE, TRUE) AS cent,

      @curRank := if(@curRank and @curCent, @curRank + 1,'No Inc') AS k,

       @prevParent := parent, @prevCent := perCent
from (
    select child.id, child.perCent, child.parent
    from likesd parent
    join likesd child
       on parent.id = child.parent
    where parent.type = 3
    order by parent.id, child.perCent desc) x
cross join (SELECT @curRank := 0, @prevParent := null, @prevCent := null) r

Answer 1

试试这个：http://sqlfiddle.com/#!2/ac996/7

select id, perCent, rank
from
(
    select id, perCent 
    , @curRank :=   
        case 
           when @prevParent = parent then
               case
                   --if parents are the same and values are the same, rank is the same
                   when @prevCent = perCent then @curRank 
                   --if same parents but different values, increment the rank
                   else @curRank + 1
               end
           --if parents are different, reset the rank
           else 1
        end rank
    , @prevParent := parent
    , @prevCent := perCent
    from 
    (
        select child.id, child.perCent, child.parent
        from likesd parent
        inner join likesd child
           on child.parent = parent.id
        where parent.type = 3
        order by parent.id
        , child.perCent desc
    ) x
    cross join (SELECT @curRank := 0, @prevParent := null, @prevCent := null) r
) y

MySql是否基于先前的值增加或不增加

1 个答案: