Select 'x'
From <The main table of the searched field, where it is defined as the PK of that table>
Where <search field> = <search value> and
EXISTS
(<sub-select with the desired condition. This is the high volume table>);
For example :
Select 'x'
From CI_UOM
Where UOM_CD = input UOM_CD and
EXISTS (select 'x'
From CI_BSEG_CALC_LN
Where UOM_CD = input UOM_CD);
Select 'x'
From CI_INSTALLATION
Where EXISTS
(<sub-select with the desired condition>) ;
CI_INSTALLATION
, since this table has only one
row.