because of being referenced by Vno column of VouchersDetail table. (b) VouchersDetail : This table is meant to store those data items of the voucher, which appear in the grid of debit or credit vouchers. However, the Total amount of voucher is not stored because it is derived data. It consists of Vno, Sno, Code, Amount and Narration as its columns.
Vno : This column is meant to store voucher number of Debit/ Credit record of VouchersMain table to which the Credit/Debit entries of vouchersDetails table are related. Its data type should be the same as that of Vno in VouchersMain table because this column refers to Vno column of vouchersMain table to maintain referential integrity. Its value cannot be null and therefore its Allow Zero Length property must be set to No with Required property being Yes . Since there can be more than one debit/credit Entry against each of the credit/debit entry of VoucherMain table, the values stored in this column cannot be unique and therefore this column alone cannot be a primary key field.
Sno : This column has been included in the table structure to store serial numbers , , … to correspond to the serial number of debit/credit entries being referred to in the grid of an accounting Voucher: Debit or Credit. Duplicate values will occur in this field also because the serial numbers of entries across the vouchers are bound to be the same. However, both the columns: vno and Sno together provide a unique value because for every voucher the entries are serially numbered and therefore unique. Both the columns together need be declared as primary key of this table.
Code : This column is meant to store the account codes, which in the context of debit voucher are debit accounts and in the context of credit voucher are credit accounts. This column is also the foreign key column because it references the primary key column of Accounts table. Its data type and properties must be the same as that of Code column of Accounts table, except that its Indexed property must be set