I need to know how to create a crosstab query - sql

Question

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.
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.)
Desired results:
AssetType Total Deployed Inventory Shipped ...
-----------------------------------------------------------
Desktop 100 75 20 5 ...
Laptop 75 56 19 1 ...
Server 60 50 10 0 ...
Some Data:
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

Answer 1

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: If you are using SQL Server 2005+ you can implement the PIVOT function.
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;
See SQL Fiddle with Demo.
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)
See SQL Fiddle with Demo
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
See SQL Fiddle with Demo
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;
See SQL Fiddle with Demo
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;
See SQL Fiddle with Demo.
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 |

Answer 2

Using a non pivot compliant DBMS (Absolute Database) I was more successful using this SQL cross-tab equivalent statement:
SELECT
sub.TypeName
, SUM(sub.[Count]) AS "Total"
, SUM(CASE WHEN AssetStatus='1' THEN sub.[Count] ELSE 0 END) AS "Deployed"
, SUM(CASE WHEN AssetStatus='2' THEN sub.[Count] ELSE 0 END) AS "Inventory"
, SUM(CASE WHEN AssetStatus='3' THEN sub.[Count] ELSE 0 END) AS "Shipped"
FROM
(
SELECT
t.TypeName
, AssetStatus
, COUNT(AssetID) AS "Count"
FROM
Assets
JOIN AssetTypes t ON t.ID = AssetType
JOIN AssetStatus s ON s.ID = AssetStatus
GROUP BY t.TypeName, AssetStatus, s.StatusName
) sub
GROUP BY sub.TypeName
;
As I realized this code (above) didn't work with MySQL I adapted my code as below executing equally well in MySQL as in my current Absolute Database. The reason is the specific NULL handling avoiding the pitfall of dBase, Paradox as well as Absolute Database generously accepting COUNT(NULL) = 0 not accepted in mainstream databases.
So believing this will execute well in most databases (handling CASE ..) this is my adapted code:
SELECT
sub.TypeName
, SUM(sub.AssetCase) AS "Total"
, SUM(CASE WHEN sub.StatusName = 'Deployed' THEN sub.AssetCase ELSE 0 END) AS "Deployed"
, SUM(CASE WHEN sub.StatusName = 'Inventory' THEN sub.AssetCase ELSE 0 END) AS "Inventory"
, SUM(CASE WHEN sub.StatusName = 'Shipped' THEN sub.AssetCase ELSE 0 END) AS "Shipped"
FROM
(
SELECT
c.TypeName
, c.StatusName
, CASE WHEN a.AssetID IS NULL THEN 0 ELSE 1 END AS "AssetCase"
FROM
(
SELECT
t.ID AS tID
, t.TypeName
, s.ID AS sID
, s.StatusName
FROM
AssetTypes t, AssetStatus s
) c
LEFT JOIN Assets a
ON a.AssetType = c.tID AND a.AssetStatus = c.sID
) sub
GROUP BY
sub.TypeName
;
Best Regards
Niels Knabe