To return the table back to the state it was in at time x, use the following plan:
| Row | Row at Time X Compared to Row Now |
Plan |
|---|---|---|
| 1 | Row existed at time X and row exists now. | Leave the row as it is. |
| 2 | It existed at time X and row exists now. | Leave the row as it is. |
| 3 | It did not exist at time X. | Delete the row. |
| 4 | It was closed at time X, and is still closed now. | Leave the row as it is. |
| 5 | It was closed at time X, and is still closed now. | Leave the row as it is. |
| 6 | It was open at time X, but is closed now. | Leave BEGIN(TT) as it is. Update END(TT) to UNTIL_CLOSED. |
| 7 | It was open at time X, but row is closed now. | Leave BEGIN(TT) as it is. Update END(TT) to UNTIL_CLOSED. |
| 8 | It did not yet exist at time X. | Delete the row. |
The following SQL will realize the plan for each of the different row states.
NONTEMPORAL DELETE tt_table where BEGIN(tt_col) > time X; NONTEMPORAL UPDATE tt_table SET tt_col = PERIOD(BEGIN(tt_col), UNTIL_CLOSED) WHERE END(tt_col) IS NOT UNTIL_CLOSED AND BEGIN(tt_col) <= time X AND END(tt_col) > time X;
Because this solution requires NONTEMPORAL SQL, nontemporal operations on temporal tables must be enabled using the DBS Control utility. Additionally, the user executing this SQL must be granted the NONTEMPORAL privilege. For more information on DBS Control see Teradata Vantage™ - Database Utilities, B035-1102. For more information on NONTEMPORAL operations, see Usage Notes.