我需要知道如何创建交叉表查询 [英] I need to know how to create a crosstab query

问题描述

我需要帮助来创建以下结果.我想到了sql枢纽，但我不知道如何使用它.看了几个例子，无法提出解决方案.也欢迎任何其他有关如何完成此操作的想法.状态列必须动态生成.

I need help creating the below results. I thought of a sql pivot but I don't know how to use it. Looked at a few examples and cannot come up with a solution. Any other ideas on how to accomplish this is also welcome. Status columns must be dynamically generated.

具有三个表，资产，资产类型，资产状态

Have three tables, assets, assettypes, assetstatus

Table: assets
assetid     int
assettag    varchar(25)
assettype   int
assetstatus int

Table: assettypes
id         int
typename   varchar(20)  (ex: Desktop, Laptop, Server, etc.)

Table: assetstatus
id         int
statusname varchar(20)  (ex: Deployed, Inventory, Shipped, etc.)

所需结果:

AssetType     Total   Deployed   Inventory  Shipped     ...
-----------------------------------------------------------
Desktop         100       75        20          5       ...
Laptop           75       56        19          1       ...
Server           60       50        10          0       ...

一些数据:

assets table:
1,hol1234,1,1
2,hol1233,1,2
3,hol3421,2,3
4,svr1234,3,1

assettypes table:
1,Desktop
2,Laptop
3,Server

assetstatus table:
1,Deployed
2,Inventory
3,Shipped

推荐答案

这种类型的转换称为枢轴.您没有指定要使用的数据库，所以我将为SQL Server和MySQL提供答案.

This type of transformation is called a pivot. You did not specify what database you are using so I will provide a answers for SQL Server and MySQL.

SQL Server::如果您使用的是SQL Server 2005+，则可以实现PIVOT函数.

SQL Server: If you are using SQL Server 2005+ you can implement the PIVOT function.

如果您想将已知数量的值转换为列，则可以对查询进行硬编码.

If you have a known number of values that you want to convert to columns then you can hard-code the query.

select typename, total, Deployed, Inventory, shipped
from
(
  select count(*) over(partition by t.typename) total,
    s.statusname,
    t.typename
  from assets a
  inner join assettypes t
    on a.assettype = t.id
  inner join assetstatus s
    on a.assetstatus = s.id
) d
pivot
(
  count(statusname)
  for statusname in (Deployed, Inventory, shipped)
) piv;

请参见带有演示的SQL小提琴.

但是，如果您有未知数量的status值，那么您将需要在运行时使用动态sql生成列列表.

But if you have an unknown number of status values, then you will need to use dynamic sql to generate the list of columns at run-time.

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT distinct ',' + QUOTENAME(statusname) 
                    from assetstatus
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT typename, total,' + @cols + ' from 
             (
                select count(*) over(partition by t.typename) total,
                  s.statusname,
                  t.typename
                from assets a
                inner join assettypes t
                  on a.assettype = t.id
                inner join assetstatus s
                  on a.assetstatus = s.id
            ) x
            pivot 
            (
                count(statusname)
                for statusname in (' + @cols + ')
            ) p '

execute(@query)

请参见带有演示的SQL小提琴

这也可以使用带有case表达式的聚合函数来编写:

This can also be written using an aggregate function with a case expression:

select typename,
  total,
  sum(case when statusname ='Deployed' then 1 else 0 end) Deployed,
  sum(case when statusname ='Inventory' then 1 else 0 end) Inventory,
  sum(case when statusname ='Shipped' then 1 else 0 end) Shipped
from
(
  select count(*) over(partition by t.typename) total,
    s.statusname,
    t.typename
  from assets a
  inner join assettypes t
    on a.assettype = t.id
  inner join assetstatus s
    on a.assetstatus = s.id
) d
group by typename, total

请参见带有演示的SQL小提琴

MySQL::该数据库没有 pivot 函数，因此您必须使用聚合函数和CASE表达式.它也没有开窗功能，因此您必须将查询稍作更改为以下内容:

MySQL: This database does not have a pivot function so you will have to use the aggregate function and a CASE expression. It also does not have windowing functions, so you will have to alter the query slightly to the following:

select typename,
  total,
  sum(case when statusname ='Deployed' then 1 else 0 end) Deployed,
  sum(case when statusname ='Inventory' then 1 else 0 end) Inventory,
  sum(case when statusname ='Shipped' then 1 else 0 end) Shipped
from
(
  select t.typename,
    (select count(*) 
     from assets a1 
     where a1.assettype = t.id 
     group by a1.assettype) total,
    s.statusname
  from assets a
  inner join assettypes t
    on a.assettype = t.id
  inner join assetstatus s
    on a.assetstatus = s.id
) d
group by typename, total;

请参见带有演示的SQL小提琴

然后，如果您需要MySQL中的动态解决方案，则必须使用准备好的语句来生成要执行的sql字符串:

Then if you need a dynamic solution in MySQL, you will have to use a prepared statement to generate the sql string to execute:

SET @sql = NULL;
SELECT
  GROUP_CONCAT(DISTINCT
    CONCAT(
      'sum(CASE WHEN statusname = ''',
      statusname,
      ''' THEN 1 else 0 END) AS `',
      statusname, '`'
    )
  ) INTO @sql
FROM assetstatus;

SET @sql 
  = CONCAT('SELECT typename,
              total, ', @sql, ' 
            from
            (
              select t.typename,
                (select count(*) 
                 from assets a1 
                 where a1.assettype = t.id 
                 group by a1.assettype) total,
                s.statusname
              from assets a
              inner join assettypes t
                on a.assettype = t.id
              inner join assetstatus s
                on a.assetstatus = s.id
            ) d
            group by typename, total');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

请参见带演示的SQL提琴.

两个数据库中的所有查询的结果都相同:

The result is the same for all queries in both databases:

| TYPENAME | TOTAL | DEPLOYED | INVENTORY | SHIPPED |
-----------------------------------------------------
|  Desktop |     2 |        1 |         1 |       0 |
|   Laptop |     1 |        0 |         0 |       1 |
|   Server |     1 |        1 |         0 |       0 |

这篇关于我需要知道如何创建交叉表查询的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！