Question

I need to write a SQL query for a report. A user can select six filters which are dynamic i.e. User can select one or two up to max six filters.

In each filter the user selects an attribute of a device from a dropdown, an operator and its value user needs to input. This constitutes a single filter, e.g:

     AttributeName  Operator    Value
     Cost           equal       480
AND  MappedName     contains    DummyString

Here “Cost” is attribute and “480” is the value and this whole thing consist of one filter . In Similar fashion user can select max. 6 filters
Also the operator between two filters are again dynamic . it can be “AND” or “OR”

In the report I need to dynamically generate a column for each filter along with some static columns, e.g. Device Name, Device Manufacture are static columns whereas the above filter are dynamic.

So the report when the user has selected two filters will look something like:

DeviceName   DeviceManufactur  Cost              MappedName    
D1           DM1               480               DummyString 
D2           DM2               480               DummyString  

In the database the attributes are stored something like:

 DeviceName   DeviceManufactur  AttributeName              AttributeValue
   D1           DM1               Cost                      480
   D1           DM1               MappedName               DummyString  
   D2           DM2               Cost                      480
   D2           DM2               MappedName               DummyString 

So when I write simple sql like

select d.name,d.manufacture,d.AttName,d.value
from Device d
where d.AttName='Cost' and d.AttValie='480'
    and d.AttName='MappedName' and d.AttValue='DummyString'

it will never give me any records although the device is associated with both the attributes.

Can anyone suggest any specific function of SQL which will help me in writing this logic efficiently.

Answer 1

I don’t think I’m really understanding your question right, but the only thing I can think of is:

SELECT d.DeviceName, d.DeviceManufactur, d.AttributeName, d.AttributeValue
FROM aDevice d
WHERE d.DeviceName IN (
    SELECT dd.DeviceName
    FROM aDevice dd
    WHERE EXISTS (SELECT 1 FROM aDevice ddd WHERE AttributeName='Cost' AND AttributeValue='480' AND ddd.DeviceName = dd.DeviceName)
    AND EXISTS (SELECT 1 FROM aDevice ddd WHERE AttributeName ='MappedName' AND AttributeValue = 'DummyString' AND ddd.DeviceName = dd.DeviceName))

This should return all information for any device which matches the query Cost = '480' AND MappedName = 'DummyString'…