T-SQL

External Article

Dynamic Data Driven Variable Hierarchical Structures in SQL

  • Article

This article describes data driven variable structure generation in SQL. The controlling data can be located higher up on the hierarchical pathway or can be located further down on the pathway producing a look-ahead operation. Multiple pathways can independently produce dynamic data driven structures and these dynamic structures can be nested allowing a very flexible and powerful dynamic automatic data structure generation capability. These different controls of structure generation can be combined.

2010-07-27

2,757 reads

External Article

Binary Trees in SQL

  • Article

A number of hierarchies and networks are most conveniently modelled as binary trees. So what is the best way of representing them in SQL? Joe Celko discards the Nested Set solution in favour of surprisingly efficient solution based on the Binary Heap

2010-07-20

4,764 reads

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Question of the Day

Checking Identities

The DBCC CHECKIDENT command is used when working with identity values. I have a table with 10 rows in it that looks like this:

TravelLogID CityID  StartDate   EndDate
1           1       2025-01-11  2025-01-16
2           2       2025-01-11  2025-01-16
3           3       2025-01-11  2025-01-16
4           4       2025-01-11  2025-01-16
5           5       2025-01-11  2025-01-16
6           6       2025-01-11  2025-01-16
7           7       2025-01-11  2025-01-16
8           8       2025-01-11  2025-01-16
9           9       2025-01-11  2025-01-16
10          10      2025-01-11  2025-01-16
The docs for DBCC CHECKIDENT say this if I run with only the table parameter: "If the current identity value for a table is less than the maximum identity value stored in the identity column, it is reset using the maximum value in the identity column. " I run this code:
DELETE dbo.TravelLog WHERE TravelLogID >= 9
GO
DBCC CHECKIDENT(TravelLog, RESEED)
GO
INSERT dbo.TravelLog
(
    CityID,
    StartDate,
    EndDate
)
VALUES
(4, '2025-09-14', '2025-09-17')
GO
What is the identity value for the new row inserted by the insert statement above?

See possible answers