Saturday, February 23, 2008

boolean column ] database@@

Q: how to you design your table columns to hold boolean flags such as isOK, isAlive, isActive, which are heavily used in where? The challenge is, no index possible, at least in sybase =} FTS. For now, assume you want to select the minority of the rows. If you want the majority, then FTS may be legitimate.

A: Basically you only care about yes/no. But I would suggest use 0 for the majority of the rows, and 1-255 or 1 ~ FFFF for the minority. Keep this column narrow -- 1 or 2 bytes, then build an index.

Even though ms sql and mysql can perhaps create an index on a binary or BIT column, it's 1) less well-supported than regular indices and 2) questionable. In an enterprise enviroment, politically safer to stick to regular indices.

http://www.sql-server-performance.com/article_print.aspx?id=347&type=art has examples.

http://sqlserver2000.databases.aspfaq.com/can-i-create-an-index-on-a-bit-column.html has examples.

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