Duplicates in temporal history table

Question

We have JCC feed that pumping data from Oracle to SQL Server 2016. For some unknown reasons there are duplicates in the history table with THE SAME start and end times. How can it happen? I tried to update record with the condition SET Column = Column. In that case I have 2 records where all the fields are the same, but start and end times are different. How can it happen that there are same datetimes?

UPDATE:

DDL:

CREATE TABLE [dbo].[LEASES](
    [LEASE_NUMBER] [CHAR](7) NOT NULL,
    [CREDIT_DECISION_CODE] [CHAR](1) NULL,
    [LEASE_APPLICATION] [CHAR](7) NULL,
    [ACCOUNT_NUMBER] [CHAR](8) NULL,
    [CELLULAR_NUMBER] [CHAR](10) NULL,
    [DEALER_CODE] [CHAR](5) NULL,
    [USERNAME] [CHAR](12) NULL,
    [LEASE_DATE] [DATETIME2](7) NULL,
    [NEW_USED_FLAG] [CHAR](1) NULL,
    [MANUFACTURER_CODE] [CHAR](6) NULL,
    [MODEL] [CHAR](10) NULL,
    [SERIAL_NUMBER_ELECTRONIC] [INT] NULL,
    [SERIAL_NUMBER_MECHANICAL] [CHAR](10) NULL,
    [CONTROL_HEAD] [CHAR](12) NULL,
    [LEASE_TERM] [SMALLINT] NULL,
    [LESSEE_CITY] [CHAR](17) NULL,
    [LESSEE_ADDRESS_1] [CHAR](30) NULL,
    [LESSEE_ADDRESS_2] [CHAR](30) NULL,
    [LESSEE_STATE] [CHAR](2) NULL,
    [LESSEE_ZIP_CODE] [CHAR](9) NULL,
    [LESSEE_NAME] [CHAR](30) NULL,
    [KEY_NAME] [CHAR](12) NULL,
    [BASE_PAYMENT] [DECIMAL](10, 2) NULL,
    [MONTHLY_SALES_TAX] [DECIMAL](10, 2) NULL,
    [INSURANCE] [DECIMAL](10, 2) NULL,
    [MONTHLY_PAYMENT] [DECIMAL](10, 2) NULL,
    [SECURITY_DEPOSIT] [DECIMAL](10, 2) NULL,
    [INVOICES_GENERATED_COUNT] [SMALLINT] NULL,
    [DATE_LAST_INVOICED] [DATETIME] NULL,
    [DATE_LAST_LATE_FEE] [DATETIME] NULL,
    [SECURITY_DEPOSITS_INVOICED] [DECIMAL](10, 2) NULL,
    [SECURITY_DEPOSITS_REFUNDED] [DECIMAL](10, 2) NULL,
    [ADVANCE_RENT] [DECIMAL](10, 2) NULL,
    [ADVANCE_SALES_TAX] [DECIMAL](10, 2) NULL,
    [TOTAL_ADVANCE_PAYMENT] [DECIMAL](10, 2) NULL,
    [AUTO_LEASE_EXPIRATION_DATE] [CHAR](4) NULL,
    [PAYMENTS_REMAINING] [SMALLINT] NULL,
    [PV_PAYMENTS_REMAINING] [DECIMAL](10, 2) NULL,
    [TAX_RATE] [DECIMAL](10, 4) NULL,
    [TAX_STATE] [CHAR](2) NULL,
    [LEASE_FACTOR] [DECIMAL](10, 4) NULL,
    [AMOUNT_FINANCED] [DECIMAL](10, 2) NULL,
    [REMARKS] [CHAR](60) NULL,
    [VOUCHER_NUMBER] [CHAR](12) NULL,
    [BILL_METHOD_ADVANCE] [CHAR](1) NULL,
    [FINANCING_PACKAGE] [INT] NULL,
    [BUYOUT_AMOUNT] [DECIMAL](10, 2) NULL,
    [BUYOUT_DATE] [DATETIME] NULL,
    [DEPRECIATION_MONTHS] [SMALLINT] NULL,
    [SALVAGE_VALUE] [DECIMAL](10, 2) NULL,
    [LAST_DEPRECIATION_DATE] [DATETIME] NULL,
    [LAST_DEPRECIATION_AMOUNT] [DECIMAL](10, 2) NULL,
    [ACCUMULATED_DEPRECIATION] [DECIMAL](10, 2) NULL,
    [BILL_METHOD_BUYOUT] [CHAR](1) NULL,
    [BUYOUT_INVOICED] [CHAR](1) NULL,
    [RECEIVED_DATE] [DATETIME] NULL,
    [LEASE_PROGRAM] [CHAR](5) NULL,
    [PAYMENTS_INCLUDED_ADVANCE] [SMALLINT] NULL,
    [SALESPERSON_CODE] [CHAR](5) NULL,
    [UNGUARANTEED_RESIDUAL_VALUE] [DECIMAL](10, 2) NULL,
    [UNEARNED_INCOME] [DECIMAL](10, 2) NULL,
    [DIRECT_COST] [DECIMAL](10, 2) NULL,
    [AMORTIZABLE_UNEARNED_INCOME] [DECIMAL](10, 2) NULL,
    [AMORTIZED_FLAG] [CHAR](1) NULL,
    [RESIDUAL_VALUE_PERCENTAGE] [DECIMAL](10, 4) NULL,
    [MINIMUM_LEASE_PAYMENTS] [DECIMAL](10, 2) NULL,
    [IMPLICIT_MONTHLY_INTEREST_RATE] [DECIMAL](10, 8) NULL,
    [AP_POSTED_FLAG] [CHAR](1) NULL,
    [AP_POSTED_DATE] [DATETIME] NULL,
    [CAPITALIZED_LEASE_FLAG] [CHAR](1) NULL,
    [LEASE_STATUS] [CHAR](1) NULL,
    [GROSS_INVESTMENT] [DECIMAL](10, 2) NULL,
    [ADVANCE_BILLED_FLAG] [CHAR](1) NULL,
    [AP_VOUCHER_NUMBER] [CHAR](12) NULL,
    [BANK_PACKAGE] [CHAR](5) NULL,
    [INSURANCE_BINDER] [CHAR](1) NULL,
    [CURRENT_BUYOUT] [DECIMAL](10, 2) NULL,
    [LEASE_AGE_YEARS] [SMALLINT] NULL,
    [GUARANTOR_NAME] [CHAR](30) NULL,
    [GUARANTOR_ADDRESS_LINE_1] [CHAR](30) NULL,
    [GUARANTOR_ADDRESS_LINE_2] [CHAR](30) NULL,
    [GUARANTOR_CITY] [CHAR](17) NULL,
    [GUARANTOR_STATE] [CHAR](2) NULL,
    [GUARANTOR_ZIP] [CHAR](9) NULL,
    [GUARANTOR_TELEPHONE] [CHAR](18) NULL,
    [GUARANTOR_SS_NUMBER] [CHAR](9) NULL,
    [GUARANTOR] [CHAR](30) NULL,
    [BILL_CYCLES_DEFER] [INT] NULL,
    [REVENUE_ACCOUNT] [CHAR](5) NULL,
    [INVOICE_TYPE] [CHAR](5) NULL,
    [CORRESPONDENCE_FLAG] [CHAR](1) NULL,
    [DOWN_PAYMENT] [DECIMAL](10, 2) NULL,
    [ADVANCE_INSURANCE] [DECIMAL](10, 2) NULL,
    [ORIGINAL_EQUIPMENT_COST] [DECIMAL](10, 2) NULL,
    [SERVICING_DEALER_CODE] [CHAR](5) NULL,
    [DEALER_BUYOUT_DATE] [DATETIME] NULL,
    [LEASE_OWNER_CODE] [CHAR](5) NULL,
    [LEASE_OWNER_DATE] [DATETIME] NULL,
    [VENDOR_CODE] [CHAR](5) NULL,
    [SPLIT_FUNDING_COUNT] [SMALLINT] NULL,
    [DEALER_AMOUNT] [DECIMAL](10, 2) NULL,
    [VENDOR_AMOUNT] [DECIMAL](10, 2) NULL,
    [SALESPERSON_AMOUNT] [DECIMAL](10, 2) NULL,
    [DEALER_OFFICE] [SMALLINT] NULL,
    [ASSESSMENT_YEAR] [SMALLINT] NULL,
    [PROPERTY_TAX_RATE] [DECIMAL](10, 4) NULL,
    [ASSESSMENT_FACTOR] [DECIMAL](10, 4) NULL,
    [MONTHLY_PROPERTY_TAX] [DECIMAL](10, 2) NULL,
    [MANAGER_CODE] [CHAR](5) NULL,
    [DEALER_BUYOUT_PROGRAM] [CHAR](5) NULL,
    [SHARED_RESID_METHOD] [CHAR](1) NULL,
    [SHARED_RESID_AMOUNT] [DECIMAL](10, 2) NULL,
    [SHARED_RESID_PERCENT] [DECIMAL](10, 4) NULL,
    [SHARED_RESID_L_AND_D] [CHAR](1) NULL,
    [SHARED_RESID_COLLECTION_TYPE] [CHAR](1) NULL,
    [SHARED_RESID_MONTHS_OVERDUE] [SMALLINT] NULL,
    [ORIGINAL_LEASE_TERM] [SMALLINT] NULL,
    [ORIGINAL_LEASE_DATE] [DATETIME] NULL,
    [ORIGINAL_BASE_PAYMENT] [DECIMAL](10, 2) NULL,
    [ORIGINAL_MINIMUM_PAYMENTS] [DECIMAL](10, 2) NULL,
    [NEW_PAYMENT_PLAN_FLAG] [CHAR](1) NULL,
    [NEW_PAYMENT_PLAN_OFFSET] [SMALLINT] NULL,
    [NEW_PAYMENT_PLAN_DATE] [DATETIME] NULL,
    [NEW_MINIMUM_PAYMENTS] [DECIMAL](10, 2) NULL,
    [BILLING_PERIOD_NUMBER] [SMALLINT] NULL,
    [BILLING_PERIOD_1_INVOICES] [SMALLINT] NULL,
    [BILLING_PERIOD_1_PAYMENT] [DECIMAL](10, 2) NULL,
    [BILLING_PERIOD_2_INVOICES] [SMALLINT] NULL,
    [BILLING_PERIOD_2_PAYMENT] [DECIMAL](10, 2) NULL,
    [BILLING_PERIOD_3_INVOICES] [SMALLINT] NULL,
    [BILLING_PERIOD_3_PAYMENT] [DECIMAL](10, 2) NULL,
    [BILLING_PERIOD_4_INVOICES] [SMALLINT] NULL,
    [BILLING_PERIOD_4_PAYMENT] [DECIMAL](10, 2) NULL,
    [BILLING_PERIOD_5_INVOICES] [SMALLINT] NULL,
    [BILLING_PERIOD_5_PAYMENT] [DECIMAL](10, 2) NULL,
    [BILLING_PERIOD_6_INVOICES] [SMALLINT] NULL,
    [BILLING_PERIOD_6_PAYMENT] [DECIMAL](10, 2) NULL,
    [EQUIPMENT_AMOUNT] [DECIMAL](10, 2) NULL,
    [SERVICE_AMOUNT] [DECIMAL](10, 2) NULL,
    [MONTHS_OF_RECOURSE] [SMALLINT] NULL,
    [VENDOR_PAID_FLAG] [CHAR](1) NULL,
    [SALESPERSON_PAID_FLAG] [CHAR](1) NULL,
    [AP_ACCOUNT] [CHAR](5) NULL,
    [GL_AP_ACCOUNT] [CHAR](4) NULL,
    [GL_OWNER_COMPANY] [CHAR](4) NULL,
    [GL_BRANCH] [CHAR](1) NULL,
    [GL_DEPARTMENT] [CHAR](2) NULL,
    [GL_EQUIPMENT] [CHAR](2) NULL,
    [GL_STATE] [CHAR](2) NULL,
    [DEALER_RECOURSE_PERCENT] [DECIMAL](10, 4) NULL,
    [VENDOR_RECOURSE_PERCENT] [DECIMAL](10, 4) NULL,
    [SALESPERSON_RECOURSE_PERCENT] [DECIMAL](10, 4) NULL,
    [NUMBER_OF_UNITS] [SMALLINT] NULL,
    [INVOICES_SUBJECT_TO_DISCOUNT] [CHAR](1) NULL,
    [ORIGINAL_LEASE_PROGRAM] [CHAR](5) NULL,
    [MISSING_PAYMENT_COUNT] [SMALLINT] NULL,
    [BROKER_CODE] [CHAR](5) NULL,
    [REVENUE_SHARING_CODE] [CHAR](5) NULL,
    [REVENUE_SHARING_FACTOR] [DECIMAL](5, 2) NULL,
    [REVENUE_SHARING_FLAG] [CHAR](1) NULL,
    [DEALER_SHARING_CODE] [CHAR](5) NULL,
    [DEALER_SHARING_FACTOR] [DECIMAL](5, 2) NULL,
    [DEALER_SHARING_FLAG] [CHAR](1) NULL,
    [CHARGEBACK_RESERVE_FLAG] [CHAR](1) NULL,
    [FUNDING_FEE] [DECIMAL](10, 2) NULL,
    [FUNDING_FEE_INVOICED_FLAG] [CHAR](1) NULL,
    [LEASE_REFERENCE] [CHAR](30) NULL,
    [ORIGINAL_LEASE_NUMBER] [CHAR](12) NULL,
    [ORIGINAL_ACCOUNT_NUMBER] [CHAR](12) NULL,
    [BASE_PAYMENT_TAXABLE] [CHAR](1) NULL,
    [DAY_TO_CHARGE_BACK] [SMALLINT] NULL,
    [LESSEE_FED_ID_NUMBER] [CHAR](9) NULL,
    [ORIGINAL_PURCHASE_PRICE] [DECIMAL](10, 2) NULL,
    [ORIGINAL_PURCHASE_DATE] [DATETIME] NULL,
    [ACQUISITION_PURCHASE_PRICE] [DECIMAL](10, 2) NULL,
    [ACQUISITION_PURCHASE_DATE] [DATETIME] NULL,
    [BROKER_REV_SHAR_AMT_OVERRIDE] [DECIMAL](10, 2) NULL,
    [DEALER_REV_SHAR_AMT_OVERRIDE] [DECIMAL](10, 2) NULL,
    [UPFRONT_TAX_FLAG] [CHAR](1) NULL,
    [UPFRONT_TAX_AMOUNT] [DECIMAL](10, 2) NULL,
    [UPFRONT_TAX_BILLED] [CHAR](1) NULL,
    [SysStart] [DATETIME2](7) GENERATED ALWAYS AS ROW START NOT NULL,
    [SysEnd] [DATETIME2](7) GENERATED ALWAYS AS ROW END NOT NULL,
PRIMARY KEY CLUSTERED 
(
    [LEASE_NUMBER] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY],
    PERIOD FOR SYSTEM_TIME ([SysStart], [SysEnd])
) ON [PRIMARY]
WITH
(
SYSTEM_VERSIONING = ON ( HISTORY_TABLE = [dbo].[LEASES_HISTORY] )
)
GO

UPDATE 2:

I can't provide the real data, however this is the query I've used to get duplicates. Note that I am GROUPing BY all columns from the table, so these are definite duplicates:

SELECT LEASE_NUMBER
     , SysStart
     , SysEnd
     , cnt
  FROM
       (   SELECT *
                , COUNT(*) cnt
             FROM dbo.LEASES_HISTORY AS l
            GROUP BY l.LEASE_NUMBER
                   , l.CREDIT_DECISION_CODE
                   , l.LEASE_APPLICATION
                   , l.ACCOUNT_NUMBER
                   , l.CELLULAR_NUMBER
                   , l.DEALER_CODE
                   , l.USERNAME
                   , l.LEASE_DATE
                   , l.NEW_USED_FLAG
                   , l.MANUFACTURER_CODE
                   , l.MODEL
                   , l.SERIAL_NUMBER_ELECTRONIC
                   , l.SERIAL_NUMBER_MECHANICAL
                   , l.CONTROL_HEAD
                   , l.LEASE_TERM
                   , l.LESSEE_CITY
                   , l.LESSEE_ADDRESS_1
                   , l.LESSEE_ADDRESS_2
                   , l.LESSEE_STATE
                   , l.LESSEE_ZIP_CODE
                   , l.LESSEE_NAME
                   , l.KEY_NAME
                   , l.BASE_PAYMENT
                   , l.MONTHLY_SALES_TAX
                   , l.INSURANCE
                   , l.MONTHLY_PAYMENT
                   , l.SECURITY_DEPOSIT
                   , l.INVOICES_GENERATED_COUNT
                   , l.DATE_LAST_INVOICED
                   , l.DATE_LAST_LATE_FEE
                   , l.SECURITY_DEPOSITS_INVOICED
                   , l.SECURITY_DEPOSITS_REFUNDED
                   , l.ADVANCE_RENT
                   , l.ADVANCE_SALES_TAX
                   , l.TOTAL_ADVANCE_PAYMENT
                   , l.AUTO_LEASE_EXPIRATION_DATE
                   , l.PAYMENTS_REMAINING
                   , l.PV_PAYMENTS_REMAINING
                   , l.TAX_RATE
                   , l.TAX_STATE
                   , l.LEASE_FACTOR
                   , l.AMOUNT_FINANCED
                   , l.REMARKS
                   , l.VOUCHER_NUMBER
                   , l.BILL_METHOD_ADVANCE
                   , l.FINANCING_PACKAGE
                   , l.BUYOUT_AMOUNT
                   , l.BUYOUT_DATE
                   , l.DEPRECIATION_MONTHS
                   , l.SALVAGE_VALUE
                   , l.LAST_DEPRECIATION_DATE
                   , l.LAST_DEPRECIATION_AMOUNT
                   , l.ACCUMULATED_DEPRECIATION
                   , l.BILL_METHOD_BUYOUT
                   , l.BUYOUT_INVOICED
                   , l.RECEIVED_DATE
                   , l.LEASE_PROGRAM
                   , l.PAYMENTS_INCLUDED_ADVANCE
                   , l.SALESPERSON_CODE
                   , l.UNGUARANTEED_RESIDUAL_VALUE
                   , l.UNEARNED_INCOME
                   , l.DIRECT_COST
                   , l.AMORTIZABLE_UNEARNED_INCOME
                   , l.AMORTIZED_FLAG
                   , l.RESIDUAL_VALUE_PERCENTAGE
                   , l.MINIMUM_LEASE_PAYMENTS
                   , l.IMPLICIT_MONTHLY_INTEREST_RATE
                   , l.AP_POSTED_FLAG
                   , l.AP_POSTED_DATE
                   , l.CAPITALIZED_LEASE_FLAG
                   , l.LEASE_STATUS
                   , l.GROSS_INVESTMENT
                   , l.ADVANCE_BILLED_FLAG
                   , l.AP_VOUCHER_NUMBER
                   , l.BANK_PACKAGE
                   , l.INSURANCE_BINDER
                   , l.CURRENT_BUYOUT
                   , l.LEASE_AGE_YEARS
                   , l.GUARANTOR_NAME
                   , l.GUARANTOR_ADDRESS_LINE_1
                   , l.GUARANTOR_ADDRESS_LINE_2
                   , l.GUARANTOR_CITY
                   , l.GUARANTOR_STATE
                   , l.GUARANTOR_ZIP
                   , l.GUARANTOR_TELEPHONE
                   , l.GUARANTOR_SS_NUMBER
                   , l.GUARANTOR
                   , l.BILL_CYCLES_DEFER
                   , l.REVENUE_ACCOUNT
                   , l.INVOICE_TYPE
                   , l.CORRESPONDENCE_FLAG
                   , l.DOWN_PAYMENT
                   , l.ADVANCE_INSURANCE
                   , l.ORIGINAL_EQUIPMENT_COST
                   , l.SERVICING_DEALER_CODE
                   , l.DEALER_BUYOUT_DATE
                   , l.LEASE_OWNER_CODE
                   , l.LEASE_OWNER_DATE
                   , l.VENDOR_CODE
                   , l.SPLIT_FUNDING_COUNT
                   , l.DEALER_AMOUNT
                   , l.VENDOR_AMOUNT
                   , l.SALESPERSON_AMOUNT
                   , l.DEALER_OFFICE
                   , l.ASSESSMENT_YEAR
                   , l.PROPERTY_TAX_RATE
                   , l.ASSESSMENT_FACTOR
                   , l.MONTHLY_PROPERTY_TAX
                   , l.MANAGER_CODE
                   , l.DEALER_BUYOUT_PROGRAM
                   , l.SHARED_RESID_METHOD
                   , l.SHARED_RESID_AMOUNT
                   , l.SHARED_RESID_PERCENT
                   , l.SHARED_RESID_L_AND_D
                   , l.SHARED_RESID_COLLECTION_TYPE
                   , l.SHARED_RESID_MONTHS_OVERDUE
                   , l.ORIGINAL_LEASE_TERM
                   , l.ORIGINAL_LEASE_DATE
                   , l.ORIGINAL_BASE_PAYMENT
                   , l.ORIGINAL_MINIMUM_PAYMENTS
                   , l.NEW_PAYMENT_PLAN_FLAG
                   , l.NEW_PAYMENT_PLAN_OFFSET
                   , l.NEW_PAYMENT_PLAN_DATE
                   , l.NEW_MINIMUM_PAYMENTS
                   , l.BILLING_PERIOD_NUMBER
                   , l.BILLING_PERIOD_1_INVOICES
                   , l.BILLING_PERIOD_1_PAYMENT
                   , l.BILLING_PERIOD_2_INVOICES
                   , l.BILLING_PERIOD_2_PAYMENT
                   , l.BILLING_PERIOD_3_INVOICES
                   , l.BILLING_PERIOD_3_PAYMENT
                   , l.BILLING_PERIOD_4_INVOICES
                   , l.BILLING_PERIOD_4_PAYMENT
                   , l.BILLING_PERIOD_5_INVOICES
                   , l.BILLING_PERIOD_5_PAYMENT
                   , l.BILLING_PERIOD_6_INVOICES
                   , l.BILLING_PERIOD_6_PAYMENT
                   , l.EQUIPMENT_AMOUNT
                   , l.SERVICE_AMOUNT
                   , l.MONTHS_OF_RECOURSE
                   , l.VENDOR_PAID_FLAG
                   , l.SALESPERSON_PAID_FLAG
                   , l.AP_ACCOUNT
                   , l.GL_AP_ACCOUNT
                   , l.GL_OWNER_COMPANY
                   , l.GL_BRANCH
                   , l.GL_DEPARTMENT
                   , l.GL_EQUIPMENT
                   , l.GL_STATE
                   , l.DEALER_RECOURSE_PERCENT
                   , l.VENDOR_RECOURSE_PERCENT
                   , l.SALESPERSON_RECOURSE_PERCENT
                   , l.NUMBER_OF_UNITS
                   , l.INVOICES_SUBJECT_TO_DISCOUNT
                   , l.ORIGINAL_LEASE_PROGRAM
                   , l.MISSING_PAYMENT_COUNT
                   , l.BROKER_CODE
                   , l.REVENUE_SHARING_CODE
                   , l.REVENUE_SHARING_FACTOR
                   , l.REVENUE_SHARING_FLAG
                   , l.DEALER_SHARING_CODE
                   , l.DEALER_SHARING_FACTOR
                   , l.DEALER_SHARING_FLAG
                   , l.CHARGEBACK_RESERVE_FLAG
                   , l.FUNDING_FEE
                   , l.FUNDING_FEE_INVOICED_FLAG
                   , l.LEASE_REFERENCE
                   , l.ORIGINAL_LEASE_NUMBER
                   , l.ORIGINAL_ACCOUNT_NUMBER
                   , l.BASE_PAYMENT_TAXABLE
                   , l.DAY_TO_CHARGE_BACK
                   , l.LESSEE_FED_ID_NUMBER
                   , l.ORIGINAL_PURCHASE_PRICE
                   , l.ORIGINAL_PURCHASE_DATE
                   , l.ACQUISITION_PURCHASE_PRICE
                   , l.ACQUISITION_PURCHASE_DATE
                   , l.BROKER_REV_SHAR_AMT_OVERRIDE
                   , l.DEALER_REV_SHAR_AMT_OVERRIDE
                   , l.UPFRONT_TAX_FLAG
                   , l.UPFRONT_TAX_AMOUNT
                   , l.UPFRONT_TAX_BILLED
                   , l.SysStart
                   , l.SysEnd
           HAVING COUNT(*) > 1
       ) a;

UPDATE 3: Ok, by this time this is new info I was able to got. We tried to catch rpc_completed events to see what was actually going on. The trace file had 7 different statements with the different event_sequence numbers. As far as I understand this means that these statements were executed in different transactions. I'll try to prepare more detailed update later, but for now the statements were following (All the statements except the final one were executed using sp_prepexec stored procedures):

There are actually 3 different states the row had, let's call them x,y,z

• UPDATE record by PK with x state -- at this point there is no such record in the DB
• UPDATE record by PK with y state-- at this point there is no such record in the DB
• INSERT record with x state
• INSERT record with y state -- this failed with PK constraint violation
• UPDATE record to the x state -- that actually didn't change any row, so the actual record didn't change
• UPDATE record to the y state -- the actual record changed
• UPDATE record to the z state using sp_execute procedure where the handle_id is the same from the previous update (updating to the z state) but the values passed via parameters are different

So at the end of these operations we have:

Original table is in z state, and the history table has something like that (the datetimes are the real values):

• x state columns, 2017-11-01 16:55:31.3358248, 2017-11-01 16:55:31.3358248
• x state columns, 2017-11-01 16:55:31.3358248, 2017-11-01 16:55:31.3358248
• y state columns, 2017-11-01 16:55:31.3358248, 2017-11-01 16:55:41.9296659

Answer 1

Temporal tables use the begin time of the transaction as the timestamp used (see Temporal Tables in MS Docs under the insert, update, and delete sections). By doing multiple updates within your transaction, or an insert followed by an update within the same transaction you will get multiple records for a given primary key value with the same start/end times.

An excerpt from the link:

UPDATES: On an UPDATE, the system stores the previous value of the row in the history table and sets the value for the SysEndTime column to the begin time of the current transaction (in the UTC time zone) based on the system clock

Here is an example that will reproduce the behaviour. Notice that there are 2 identical entries for Miniature Widgets in the ProductsHistory table for ProductId = 2. Also note that although the updates for ProductId = 1 did not change the value, they still created identical history table records.

create table test.Products (
        ProductId       int not null primary key,
        ProductName     nvarchar(100) not null,
        EffectiveDate   datetime2(7) generated always as row start hidden not null,
        EndingDate      datetime2(7) generated always as row end hidden not null,
        period for system_time (EffectiveDate, EndingDate)
        )
        with (system_versioning = on (history_table = test.ProductsHistory));

go

begin tran

insert  test.Products (ProductId, ProductName) values
        (1, N'Widgets'),
        (2, N'Miniature Widgets');

update  test.Products set ProductName = 'Tiny Widgets' where ProductId = 2;
update  test.Products set ProductName = 'Miniature Widgets' where ProductId = 2;
update  test.Products set ProductName = 'Tiny Widgets' where ProductId = 2;
update  test.Products set ProductName = 'Widgets' where ProductId = 1;
update  test.Products set ProductName = 'Widgets' where ProductId = 1;

commit tran

select  p.ProductId, p.ProductName, p.EffectiveDate, p.EndingDate
from    test.Products for system_time all p;

select  *
from    test.ProductsHistory;