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Re: [OT] SQL and Perl

Антон wrote:
There are (a) over 400 threads that have to be deleted entirely.

There are also (b) over 800 threads in which specific records
have to be deleted (over 2,000 such records in total).

I compiled a list of threads (a) and a list of threads (b). For each,
I wrote a Perl script that reads and stores each object's name and number in a variable, one at a time. Threads are referred to by their IDs assigned during their creation, and records are referred to by their count numbers. This information could have been useful for deleting data from the forum's database if only a delete function was

You would be much better off asking this at the website of the forum software you are using; there is probably very little anyone on this list can do to help you. If you do not have experience with RDBMSs or SQL, this is not an uncomplicated task you are asking about.

OK, if I understand you correctly, by "thread" you mean "a thread of discussion in an online forum" rather than "thread" as in "a process may have one or more threads".

The problem is, if we are speaking about SQL and any given generic DBMS (i.e. "database"), there are not any SQL commands for dealing with "threads" directly as an abstract concept.

Probably (hopefully!), the database will have tables. Tables will have rows of data divided into columns. For example, there may be a table named "Threads" which has a column named "thread_id" and maybe a column named "thread_name".

And if by "records" you mean "messages in a thread", then the problem is similar. In the database, records are probably not "in" a thread. There might be, for example, a table named "Messages" which has columns message_id, thread_id, meaning respectively the unique id of the message and the id of the thread in which it is located.

The problem again, however, is that it could also just as easily be nothing like what I have described. You need information about the tables in the database, and the columns in each table.

1) What SQL commands are used for deleting threads entirely?

To delete rows from a table you would use the SQL DELETE command.

e.g: DELETE FROM Threads WHERE thread_id=5;

2) What SQL commands are used for deleting specific records in a

Again, you will use the DELETE command. If there is a table for messages, and each message has an id ("count"?) that is unique across all thread, it might be as simple as:

DELETE FROM Messages WHERE message_id=84834;

3) How can those commands be run from within a Perl script mentioned above?

First you need to determine what type of database it is. This might be something like "MySQL" or "PostgreSQL".

Then, check CPAN (cpan.org). CPAN has an entire section devoted to database interface modules.


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