Unique Index that Allows NULLS

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CREATE UNIQUE INDEX idx_license_id 
   ON Person(DrivingLicenseID) WHERE DrivingLicenseID IS NOT NULL
GO

This schema allows for a 0..1 relationship - people can have zero or one driving licenses and each license can only belong to one person

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Indexes:

*Indexes

*Creating an Index

*0Clustered Unique and Sorted Indexes

*Sorted Index

*Dropping an Index or Disabling and Rebuilding it

*Partial or Filtered Index

*Inserting with a Unique Index

*Rebuild index

*SAP ASE Drop index

*Unique Index that Allows NULLS

*Clustered index

*Non clustered index

Table Of Contents

0Getting started with SQL

1SELECT

2JOIN

3Example Databases and Tables

5Indexes

10INSERT

14Filter results using WHERE and HAVING

15Window Fnctions

16Common Table Expressions

17Views

18LIKE operator

19Functions Aggregate

20DELETE

26MERGE

28Finding Duplicates on a Column Subset with Detail

38SQL Group by vs. Distinct

39Table Design

40CROSS APPLY and OUTER APPLY

41Synonyms

42CREATE database

43SKIP TAKE pagination

44EXPLAIN and DESCRIBE

47NULL

51DROP or DELETE database

52EXCEPT

53TRYCATCH

54XML

55GRANT and REVOKE

56Functions ScalarSingle Row