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From:Ken Cobler Date:April 21 1999 10:36pm
Subject:Indexing with NULL in column
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I've read in the manual that indexing on a column containing NULLs is not
allowed in MySQL.  I have a database that I'd like to move from Access to MySQL,
however, a couple of columns that are to be transfered contain NULLs.  In
Access, the speed for searching records based upon these columns was
greatly improved when the columns were indexed (Access does allow columns
to be indexed with NULLs).

The main goal is to improve the query speed through MySQL.  If setting global
parameters allowing for internal cacheing is the answer (rather than indexing),
let me know.  Otherwise, how do I accomplish a speed up of a query that 
uses a column which contains NULLs ?

If the solution is to work on the isam code, to allow indexing on columns
with NULLs, I'm willing to work on that code.  I've developed a B-tree index
ASCII database in C.  Where would I begin to examine the code ?  What pitfalls
might in encounter ?  

Need a little help/guidance from experienced MySQL people.

BTW: I have MySQL 3.22.21 running on Linux 2.0.36.  I use ODBC to connect
Access '97 to MySQL (works great).  I have 12 years experience writing
C/Unix/database code (worked on the kernel at AT&T Bell Labs). 

Ken Cobler
Indexing with NULL in columnKen Cobler22 Apr
  • Re: Indexing with NULL in columnThimble Smith22 Apr
  • Indexing with NULL in columnMichael Widenius22 Apr