If user select 1 value, it should bring relevant record for that selected value along with 2 default values relevant records without user selection..

[JayakumarNaganathan]

Load full table data via script from BQ.

From the report, If user select 1 value, it should bringthat  relevant record for that selected value.

Along with 2 default values relevant records without user selection

Refer the below image:

Scenario 1: After full table data are loaded via script from BQ

As a User, From the column 'Filter column 2' - Selected the value as 2023-03

Expected output:  Along with selected value 'AU' default values should include like (OR condition) without selection by users output like DEF1 & DEF2

Scenario 2:

As a User,  From the column 'Filter column 2' - Selected the value as 2021-01

Expected output:  Along with selected value 'AO' default values should include like (OR condition) without selection by users output like DEF1& DEF2

Need expert support - To resolve the user request.

[marcus_sommer]

You may combine fixed values with possible values, for example like:

only({< Column2 *= {'0', 'ST'}>} OutputField)

[JayakumarNaganathan]

Thanks marus_sommer

Where to mention this piece of code (({< Column2 *= {'0', 'ST'}>} OutputField)) you replied to me 

[marcus_sommer]

Maybe as expression within a table-chart. Depending on your view-requirements you may need to include such logic within each expression and/or within a calculate dimension. Further the example covers just a single field - if more fields as dimensions and/or selections are involved and/or there are further conditions they would be needed to included there, too.

It could become easily more complex - therefore you should have very good reasons for such kind of usability. Personally I could only recommend to skip all such logic and the user selects always directly whats wanted.