Creating SNMP table DCI
SNMP table DCI defined by two parts - base OID and column definitions. Base OID is used to scan all possible instances (rows). Instance is considered a suffix obtained during walk on base OID. For example, for interface table (.1.3.6.1.2.1.2.2) you should select ifIndex (.1.3.6.1.2.1.2.2.1.1) as base OID. Walk will provide instances like .1, .2, .3 and so on. Then you can set base OIDs for columns in a way that after concatenation with discovered instance values they render into valid OID. For example, for interface description column from ifTable you should use .1.3.6.1.2.1.2.2.1.2 - it will be concatenated with interface index and became correct OID.
NB: base OID should return at least some values (shouldn't be empty row)
Below is screenshots of working interface table configuration: