SAP table SKB1 is part of the General Ledger Accounting module and stores G/L account master data specific to individual company codes. It contains information that controls how a G/L account is managed and processed within a particular company code, such as account currency, tax-related settings, reconciliation accounts, and other configuration data. This table ensures that G/L accounts are aligned with the financial requirements of each company code in SAP. More general, chart of accounts level configuration, can be found in SAP table SKA1 (G/L Account Master (Chart of Accounts)).
SAP table SKB1 has 3 primary key fields being MANDT,BUKRS,SAKNR.
If you are only analysing data from a single SAP instance you may omit field MANDT in your relationships as it will be the same across the entire dataset. On the other hand, if you are combining data from multiple SAP instances you need to take MANDT into account.