MySQL GROUP BY 与特定条件

Question

I'm using MySQL 5.5 . This is my query, the first part shows info about the company and it's vehicles, and the second part shows only company info.

I did the UNION part because some smallClients doesn't have any vehicles, and since at the first part it join with vehicles, those ones didn't appear.

What is the problem, some registers from the first and second part have the same smallClient, and since at the vehicles part I'm already showing company info, I would like to group by, only if they are the same idClient and the same department, and numberPlate is not null (if it's null it's ok, I just want to remove those registers which are redundant cause info it's already showing in vehicle part).

Some companies can have more than one number plate too, and they cannot be grouped, cause each number plate has it's own documentation (this query is smaller than the real one).

What results looks like now:

idClient  company          department    numberplate
3345      TONY FERGUSON    Commercial    null
3345      TONY FERGUSON    Financial     null
3345      TONY FERGUSON    Commercial    8453JVD

In this example, the first register should be gone, because this client has a numberPlate, and the register with the same department (first one), is redundant cause third registers shows the same.

Another example:

idClient  company          department               numberplate
1267      TERRY SL         Distribution - France    null
1267      TERRY SL         Distribución - France    6381JHZ
1267      TERRY SL         Forwarding UK            null
1267      TERRY SL         Forwarding UK            6381JHZ

In this case, first and third register should dissapear, hope I explained all propertly.

This is my query:

select  
    idClient as "IdClient",
    Company  as "Company",         
    if (Department is null, "", Department) as "Department",
    Numberplate,               
 from      
    (select
         sc.idClient as idclient,
         sc.businessname as company,     
         d.name as department,          
         v.numberplate as numberPlate,               
    from entity_type et
         join bigClient bc on bc.idClient=et.idClient
         join smallClient sc on sc.idclient=bc.idClientAssociated
         join clientVehicle cv on cv.idClientVehicle=sc.idClientVehicle
         join vehicle v on v.idVehicle=cv.idVehicle    
         join active_vehicle av on av.idEntityType=et.idEntityType and av.idClientVehicle=cv.idClientVehicle 
         left join department d on d.idDepartment=et.idDepartment   
         where bc.idClient=1234   
    UNION
    select 
         c.idClient as idclient,
         c.businessname as empresavehicle,      
         cd.name as departament,      
         null as matricula,          
        from entity_type et
         join bigClient bc on bc.idClient=et.idClient
         join smallClient sc on sc.idclient=bc.idClientAssociated
         join active_c ac on ac.idEntityType=et.idEntityType and ac.idBigClient=bc.idBigClient   
         left join department d on d.idDepartment=et.idDepartment        
         where bc.idClient=1234) t
    order by company,numberplate;

Answer 1

You can use the analytical function count as follows:

select * from
(select  
    idClient as "IdClient",
    Company  as "Company",         
    if (Department is null, "", Department) as "Department",
    Numberplate,
    count(Numberplate) over (partition by idClient,company,department) as cnt
  from
    .... rest of your query ....
) t
where cnt = 0 or (cnt>0 and Numberplate is not null)

Answer 2

The @Popeye solution should to work in MySQL 8.o or greater, for MySQL 5.x I can to advice next:

select  
    idclient as "IdClient",
    company  as "Company",         
    if (department is null, "", department) as "Department",
    group_concat(numberplate) as ,
 from      
    (select
         sc.idClient as idclient,
         sc.businessname as company,     
         d.name as department,          
         v.numberplate as numberplate,               
    from entity_type et
         join bigClient bc on bc.idClient=et.idClient
         join smallClient sc on sc.idclient=bc.idClientAssociated
         join clientVehicle cv on cv.idClientVehicle=sc.idClientVehicle
         join vehicle v on v.idVehicle=cv.idVehicle    
         join active_vehicle av on av.idEntityType=et.idEntityType and av.idClientVehicle=cv.idClientVehicle 
         left join department d on d.idDepartment=et.idDepartment   
         where bc.idClient=1234   
    UNION
    select 
         c.idClient as idclient,
         c.businessname as company,      
         cd.name as departament,      
         null as numberplate,          
        from entity_type et
         join bigClient bc on bc.idClient=et.idClient
         join smallClient sc on sc.idclient=bc.idClientAssociated
         join active_c ac on ac.idEntityType=et.idEntityType and ac.idBigClient=bc.idBigClient   
         left join department d on d.idDepartment=et.idDepartment        
         where bc.idClient=1234) t
    group by idClient, Company, Department
    order by company,numberplate;

this query should work with one limitation - in case different numberplate it return one concatinated string