IF, then, else in SQL query to combine multiple columns - sql

Question

I currently have an SQL query that is used to create a matter report for our firms. The problem with it at the moment is that it creates six columns for client/party details which could be reduced to three columns to minimise confusion for the secretaries that will review before the report is used in marketing.
There's three client types - individual, joint party or organisation.
The six columns in the report are ClientFirstName, ClientLastName, ClientEmail (which are all populated if the ClientType is Individual) and PartyFirstName, PartyLastName, PartyEmail (which are all populated if the ClientType is Joint Part or Organisation - sometimes multiple results for each party member).
Here's the query:
SELECT DISTINCT
-- setup columns
[cases].[reference] as MatterNumber,
[dd_entity_d2].[type] as ClientType,
[dd_client].[clientname] as MatterName,
etClient.FirstName as ClientFirstName,
etClient.LastName as ClientLastName,
[dd_entity_d2].[email] as ClientEmail,
[dd_entity_d4].[firstname] as PartyFirstName,
[dd_entity_d4].[lastname] as PartyLastName,
[dd_entity_d4].[email] as PartyEmail,
etActing.[PreferredName] ActingPerson,
[cases].[category] as MatterType,
mt.CreatedOn as MatterOpened,
case mt.[Status]
when 0 then 'In Progress'
When 1 then 'On Hold'
when 2 then 'Completed'
when 3 then 'Not Proceeding'
else 'Unknown' end as MatterStatus
-- mt.LastUpdatedOn as LastModified,
-- end columns
-- setup data
FROM PracticeEvolve_doc.dbo.[cases]
INNER JOIN PracticeEvolve_c1.dbo.DocumaticsMap dm on dm.DocumaticsID = [cases].ID and dm.Entitytype = 'Matter'
INNER JOIN PracticeEvolve_c1.dbo.[Matter] mt on mt.Matterid = dm.ClickOneID
INNER JOIN PracticeEvolve_c1.dbo.[Client] cl on mt.ClientID = cl.ClientID
INNER JOIN PracticeEvolve_c1.dbo.[Entity] etClient on cl.EntityID = etClient.EntityID
LEFT JOIN PracticeEvolve_c1.dbo.EmployeeMatter emActing on emActing.MatterID = mt.MatterID and emActing.AssociationTypeID = 15
LEFT JOIN PracticeEvolve_c1.dbo.Employee eActing on eActing.EmployeeID = emActing.EmployeeID
LEFT JOIN PracticeEvolve_c1.dbo.Entity etActing on etActing.EntityID = eActing.EntityID
LEFT JOIN PracticeEvolve_doc.dbo.[dd_client] ON [dd_client].[id]=[cases].[clientid]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_manytomany] AS [dd_manytomanydd_entity_d2] ON [dd_manytomanydd_entity_d2].[fkid] = [dd_client].[fk_entities]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_entity] as [dd_entity_d2] ON [dd_entity_d2].[id] = [dd_manytomanydd_entity_d2].[pkid]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_manytomany] AS [dd_manytomanydd_party_d3] ON [dd_manytomanydd_party_d3].[fkid] = [dd_entity_d2].[fk_parties]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_party] as [dd_party_d3] ON [dd_party_d3].[id] = [dd_manytomanydd_party_d3].[pkid]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_manytomany] AS [dd_manytomanydd_entity_d4] ON [dd_manytomanydd_entity_d4].[fkid] = [dd_party_d3].[fk_entity]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_entity] as [dd_entity_d4] ON [dd_entity_d4].[id] = [dd_manytomanydd_entity_d4].[pkid]
-- end data
-- setup filters
WHERE [cases].[deleted]=0
AND DATEPART(m, mt.CreatedOn) = DATEPART(m, DATEADD(m, -1, getdate()))
AND DATEPART(yyyy, mt.CreatedOn) = DATEPART(yyyy, DATEADD(m, -1, getdate()))
-- AND mt.CreatedOn >= '2017-05-16'
-- AND [dd_entity_d2].[type] = 'Individual'
-- AND mt.LastUpdatedOn >= '2017-04-02'
-- AND mt.[status] = 0
-- end filters and query
What I'd like to do is have it just use the columns FirstName, LastName and Email so that it is populated with the individual's details if the ClientType is individual, or populated with the joint party's/organisation's details if the ClientType is something other than Individual.
Is this possible?
(as a bit of a disclaimer - I'm a novice with database queries, so may not know how to implement a specific statement or string)

Answer 1

You can use Case Statement. I assumed Client type is stored as text but you can change 'individual' to appropriate value.
SELECT DISTINCT
-- setup columns
[cases].[reference] as MatterNumber,
[dd_entity_d2].[type] as ClientType,
[dd_client].[clientname] as MatterName,
CASE WHEN [dd_entity_d2].[type] ='Individual' THEN etClient.FirstName ELSE [dd_entity_d4].[firstname] END AS FirstName,
CASE WHEN [dd_entity_d2].[type] ='Individual' THEN etClient.LastName ELSE [dd_entity_d4].[lastname] END AS LastName,
CASE WHEN [dd_entity_d2].[type] ='Individual' THEN [dd_entity_d2].[email] ELSE [dd_entity_d4].[email] END AS Email,
etActing.[PreferredName] ActingPerson,
[cases].[category] as MatterType,
mt.CreatedOn as MatterOpened,
case mt.[Status]
when 0 then 'In Progress'
When 1 then 'On Hold'
when 2 then 'Completed'
when 3 then 'Not Proceeding'
else 'Unknown' end as MatterStatus
-- mt.LastUpdatedOn as LastModified,
-- end columns
-- setup data
FROM PracticeEvolve_doc.dbo.[cases]
INNER JOIN PracticeEvolve_c1.dbo.DocumaticsMap dm on dm.DocumaticsID = [cases].ID and dm.Entitytype = 'Matter'
INNER JOIN PracticeEvolve_c1.dbo.[Matter] mt on mt.Matterid = dm.ClickOneID
INNER JOIN PracticeEvolve_c1.dbo.[Client] cl on mt.ClientID = cl.ClientID
INNER JOIN PracticeEvolve_c1.dbo.[Entity] etClient on cl.EntityID = etClient.EntityID
LEFT JOIN PracticeEvolve_c1.dbo.EmployeeMatter emActing on emActing.MatterID = mt.MatterID and emActing.AssociationTypeID = 15
LEFT JOIN PracticeEvolve_c1.dbo.Employee eActing on eActing.EmployeeID = emActing.EmployeeID
LEFT JOIN PracticeEvolve_c1.dbo.Entity etActing on etActing.EntityID = eActing.EntityID
LEFT JOIN PracticeEvolve_doc.dbo.[dd_client] ON [dd_client].[id]=[cases].[clientid]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_manytomany] AS [dd_manytomanydd_entity_d2] ON [dd_manytomanydd_entity_d2].[fkid] = [dd_client].[fk_entities]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_entity] as [dd_entity_d2] ON [dd_entity_d2].[id] = [dd_manytomanydd_entity_d2].[pkid]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_manytomany] AS [dd_manytomanydd_party_d3] ON [dd_manytomanydd_party_d3].[fkid] = [dd_entity_d2].[fk_parties]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_party] as [dd_party_d3] ON [dd_party_d3].[id] = [dd_manytomanydd_party_d3].[pkid]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_manytomany] AS [dd_manytomanydd_entity_d4] ON [dd_manytomanydd_entity_d4].[fkid] = [dd_party_d3].[fk_entity]
LEFT JOIN PracticeEvolve_doc.dbo.[dd_entity] as [dd_entity_d4] ON [dd_entity_d4].[id] = [dd_manytomanydd_entity_d4].[pkid]
-- end data
-- setup filters
WHERE [cases].[deleted]=0
AND DATEPART(m, mt.CreatedOn) = DATEPART(m, DATEADD(m, -1, getdate()))
AND DATEPART(yyyy, mt.CreatedOn) = DATEPART(yyyy, DATEADD(m, -1, getdate()))
-- AND mt.CreatedOn >= '2017-05-16'
-- AND [dd_entity_d2].[type] = 'Individual'
-- AND mt.LastUpdatedOn >= '2017-04-02'
-- AND mt.[status] = 0
-- end filters and query