How to create a generic query depending on user inputs to return distinct set

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SQL

Hi there,

I appreciate if someone can assist me with my SQL queries.

I require assistance in creating a generic query which will work depending on the parameters given.

Here is my following table structure I have to work with:
Table1
MachId
MachCode
MachLinkType(Can be of Type 'ROBOT', 'MINI')

Table2
StatId
Stat_GDU_Code(linked to the Table 3)
Stat_MachCode(linked to Table1)

Table3
GDU_Id
GDU_prefix
GDU_code
GDU_description
Note The GDU_CODE is not unique. The GDU_prefix and GDU_id have to be unique.

Table4
PlacId
Plac_Mach_Code(links to MachCode)
PlacType(e.g FROD, PLACK)
PlacDescription

If the MachLinkType is 'ROBOT' then I look in Table 1 and Table 4 to get the description etc:

SELECT MachId, MachCode, MachLinkType, PlacType, Plac_Description 
from Table1 INNER JOIN Table4
ON Table1.MachCode = Table4.Plac_Mach_Code
RTRIM(MachLinkType)= 'ROBOT' AND RTRIM(PlacType)= 'FROD'

Now if the value is not ROBOT then I have to interrogate 3 tables (Table 1, Table 2 and Table 3) but I have 2 issues with this:

Firstly if I include the GDU_Description fields I get duplicate records.

I have tried using 'distinct' on the Table1.MachId but I think that is incorrect way of using it for my query.

I need the description of the record from Table 3 in regards to the output I am trying to generate.

Below is my query if the value provided by the user isn't PLAC:

SELECT distinct(MachId), MachCode, MachLinkType, Stat_GDU_Code, GDU_Description 
from Table1 INNER JOIN Table2
ON Table1.MachCode = Table2.Stat_MachCode
INNER JOIN Table2 ON
Table3.GDU_Code = Table2.Stat_GDU_Code
WHERE RTRIM(MachLinkType) = 'MINIBOT' AND RTRIM(Stat_GDU_Code) = '31A'

Secondly, if user provides ROBOT and MINIBOT types how can I combine the two queries above in an appropriate manner so I can retrieve results for both ROBOT and MINIBOT types.

I appreciate if someone can assist me please?

This is the sort of output i want to generate in my user control:

MachineReference:123
MachineCode: EPIS
MachineLinkType: AUTONOMOUS
MachinePartCode: 31A
MachineDescription: 'Test Description'.

Regardless of which table the respective data lives in i would like to use assign the data to those 5 labels.

Thanks,