Comments on: SQL Optimization Tips/Questions

By: Keith

Keith — Wed, 09 Dec 2009 03:46:36 +0000

For question 1, this would depend on the collation setting on the server etc. If the system was set up to be case sensitive and you were performing a user search you would need to use the upper or lower or handle this issue in another tier of the system (not recommended … coupling)

By: Markus Wollny

Markus Wollny — Tue, 08 Dec 2009 08:52:57 +0000

I was irritated by the fact that you don’t actually say which RDBMS you’re talking about – I guess it’s Microsoft SQL Server, the ‘Transact-SQL’ mention really gave it away. On more general terms:

1b might actually be the best in case your RDBMS supports functional indexes and you have set such a functional index on lower(column_name). This is an option with PostgreSQL and Oracle, though not (yet) for MySQL, don’t know about other RDBMS support for functional indexes – Microsoft SQL Server may not be among the lucky lot here.

As to 2c: Again, if you have functional indexes available, such a mixing of column_name and function may not prevent you from using indexes, though in this case it surely will, GetDate() being a volatile function (unlike lower()).

By: Ankit Goyal

Ankit Goyal — Sun, 06 Dec 2009 08:09:27 +0000

Hello Martin,
Yes you are correct. But queries were written to stress the fact that we should avoid using functions and “*” in queries and not logic

By: Martin Smith

Martin Smith — Sat, 05 Dec 2009 23:08:28 +0000

1a and 1b are not equivalent. 1b will not return data for Name or any other mixed case ‘NaMe’ .

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