可以办到
可以使用现有数据（包括日期）初始化 SQL 临时（系统版本化）表和历史记录。它只涉及跳过一堆愚蠢的箍。希望微软将来能给我们一个更好的方法来用现有的历史数据初始化这些表。
将现有数据放入具有特定 SYSTEM_TIME 日期的这些表中的技巧的简短版本是：
- 将系统版本控制添加到表中。
- 收集数据以添加到系统版本化表，其中包含用于填充目标表中的 SYSTEM_TIME 列的列。请注意，SYSTEM_TIME 值将位于 UTC 时区，因此可能需要执行 AT TIME ZONE 'UTC' 之类的操作来获取正确的日期。
- 关闭系统版本控制。
- 为 CRUD 操作创建动态 SQL。
- 重新打开系统版本控制。
这是该过程的简化示例：
-- System versioned table: dbo.ManagerList
-- Primary Key: ManagerName
-- History table: dbo.ManagerList_History
-- SYSTEM_TIME columns: _PeriodStart, _PeriodEnd
-- Table with Data to Import: #SourceData
DECLARE @Script varchar(max)
-- Disable system versioning
ALTER TABLE dbo.ManagerList SET (SYSTEM_VERSIONING = OFF);
ALTER TABLE dbo.ManagerList
DROP PERIOD FOR SYSTEM_TIME;
-- Prepare source data (in temporary table #SourceData)
UPDATE A
SET _PeriodEnd = B.PeriodEnd
FROM #SourceData as A
INNER JOIN
(
SELECT ManagerName,
_PeriodStart,
_PeriodEnd =
LEAD(_PeriodStart, 1, datetime2fromparts(9999,12,31,23,59,59,9999999,7)) OVER
(
PARTITION BY ManagerName
ORDER BY _PeriodStart
)
) as B
ON A.ManagerName = B.ManagerName
AND A._PeriodStart = B._PeriodStart
-- DELETE from System-Versioned table
DELETE A
FROM dbo.ManagerList as A
WHERE NOT EXISTS
(
SELECT 1
FROM #SourceData
WHERE ManagerName = A.ManagerName
)
-- UPDATE script for System-Versioned table
SET @Script =
'UPDATE A ' +
'SET FavoriteColor = B.FavoriteColor, ' +
' _PeriodStart = B._PeriodStart ' +
'FROM dbo.ManagerList as A ' +
' INNER JOIN #SourceData as B ' +
' ON A.ManagerName = B.ManagerName ' +
'WHERE B._PeriodEnd > datefromparts(9999,12,31) ' +
' ( ' +
' A.ManagerName != B.ManagerName ' +
' OR A._PeriodStart != B.PeriodStart ' +
' )'
EXEC (@Script)
-- UPDATE script for System-Versioned table
SET @Script =
'UPDATE A ' +
'SET FavoriteColor = B.FavoriteColor, ' +
' _PeriodStart = B._PeriodStart ' +
'FROM dbo.ManagerList ' +
' INNER JOIN #SourceData as B ' +
' ON A.ManagerName = B.ManagerName ' +
'WHERE B._PeriodEnd > datefromparts(9999,12,31) ' +
' AND (' +
' A.FavoriteColor != B.FavoriteColor ' +
' OR A._PeriodStart != B.PeriodStart ' +
' )'
EXEC (@Script)
-- INSERT script for System-Versioned table
SET @Script =
'INSERT dbo.ManagerList ' +
'( ' +
' ManagerName, ' +
' FavoriteColor, ' +
' _PeriodStart ' +
') ' +
'SELECT ManagerName, ' +
' FavoriteColor, ' +
' _PeriodStart ' +
'FROM #SourceData as A ' +
'WHERE _PeriodEnd > datefromparts(9999,12,31) ' +
' AND NOT EXISTS ' +
' ( ' +
' SELECT 1 ' +
' FROM dbo.ManagerList ' +
' WHERE ManagerName = A.ManagerName ' +
' )'
EXEC (@Script)
-- DELETE script for History table
SET @Script =
'DELETE A ' +
'FROM dbo.ManagerList_History as A ' +
'WHERE NOT EXISTS ' +
' ( ' +
' SELECT 1 ' +
' FROM #SourceData ' +
' WHERE ManagerName = A.ManagerName ' +
' AND _PeriodEnd < datefromparts(9999,12,31) ' +
' )'
EXEC (@Script)
-- UPDATE script for History table
SET @Script =
'UPDATE A ' +
'SET FavoriteColor = B.FavoriteColor ' +
'FROM dbo.ManagerList_History as A' +
' INNER JOIN #SourceData as B ' +
' ON A.ManagerName = B.ManagerName ' +
' AND A._PeriodStart = B._PeriodStart ' +
'WHERE B._PeriodEnd < datefromparts(9999,12,31) ' +
' AND (' +
' A.FavoriteColor != B.FavoriteColor' +
' )'
EXEC (@Script)
-- INSERT script for History table
SET @Script =
'INSERT dbo.ManagerList ' +
'( ' +
' ManagerName, ' +
' FavoriteColor, ' +
' _PeriodStart ' +
') ' +
'SELECT ManagerName, ' +
' FavoriteColor, ' +
' _PeriodStart ' +
'FROM #SourceData as A ' +
'WHERE _PeriodEnd < datefromparts(9999,12,31) ' +
' AND NOT EXISTS ' +
' ( ' +
' SELECT 1 ' +
' FROM dbo.ManagerList_History ' +
' WHERE ManagerName = A.ManagerName ' +
' AND _PeriodStart = A._PeriodStart ' +
' )'
EXEC (@Script)
-- Re-enabling system versioning
-- Note: Making this dynamic SQL solves compiler error
SET @Script =
'ALTER TABLE dbo.ManagerList ' +
'ADD PERIOD FOR SYSTEM_TIME (_PeriodStart, _PeriodEnd)';
EXEC (@Script)
ALTER TABLE dbo.ManagerList
SET (SYSTEM_VERSIONING = ON (HISTORY_TABLE = dbo.ManagerList_History));
主要问题似乎是编译器并不总是能够识别系统版本表上的东西何时关闭，并且不会让非动态 SQL 编译或运行。不知道为什么可以使用动态 SQL，但我很高兴它可以做到。
在最初从现有表中填充表之后，所有关于不修改 SYSTEM_TIME 日期或删除历史记录中的记录的限制在世界范围内都是有意义的。
希望这可以帮助某人。
