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The Practical Problems of Determining Equality and Equivalence in SQL

In theory, it is easy to determine whether data is equal to, greater than or lesser than a value. Real-world data types can be surprisingly tricky, even for gauging data equivalence. Because SQL cannot remain aloof from any application's data types, you need to be aware of the ways and pitfalls of individual datatypes and how you can test for equality, equivalence, similarity, identity and all that jazz. Joe Celko discusses.

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Question of the Day

RegEx Functions IV

I have this data in a table in a SQL Server 2025 database:

EmailAddressID EmailAddress
7              dylan0@ADVENTURE-WORKS.COM
8              Diane1@ADVENTURE-WORKS.COM
If I run this query, which row(s) are returned?
SELECT top 10
 *
 FROM person.EmailAddress
 WHERE REGEXP_LIKE(EmailAddress, '^D', 'i')
 AND BusinessEntityID IN (7,8)

See possible answers