Reader Feedback and Insights: One-Row Table Still Needed

December 6, 2002 Timothy Prickett Morgan

Hey, Ted:

In the article, “Overlooking the Obvious,” which published in the November 8 issue of Midrange Guru, you asked the question, “does anybody have a use for a one-row, one-column table?”

I’ll still need one for the near future.

• I don’t have a C compiler or interactive SQL, so I’m stuck without variables.
• I run a lot of test scripts initially in Operations Navigator (cwbundbs), and it’s handy for testing the duration of things:

select 'start',now() from onerec;
update some long thing with a few statements;
select 'end',now() from onerec;

ONEREC is my one-row table. I

Get Rid of Old IFS Files, Take Two

December 6, 2002 Timothy Prickett Morgan

Hey, Ted:

I have worked with Unix for 18 years. Here is a Qshell command that will remove any file that is more than seven-days old. (It also checks subdirectories).

Here is the command:

find * -type f -mtime +7 -exec rm {} ;

— Mike

I am grateful to Mike for providing that tip.

Now, let’s break that command down so we can understand it.

The find command locates files that match certain criteria. In this case, find looks for files that have not been modified in the last seven days.

The find command may be followed by options.

Performance of the SQL LIKE Predicate

December 6, 2002 Timothy Prickett Morgan

Hey, Ted:

I have heard that SQL’s LIKE predicate cannot take advantage of indexes. Can I use indexes to speed up a query that uses LIKE?

— Jim

LIKE has long had the reputation of being a poor performer, probably because of the way it has been implemented on various platforms. In some cases, using LIKE in a query guarantees a database scan (e.g., reading the entire table).

If the expression begins with a wildcard character–an underscore ( _ ) to represent a single character, a percent sign (%) to represent multiple characters–then the query will require a database scan