Understanding sqlplus syntax

From: Jon <jhoug2_at_hotmail.com>
Date: 31 Dec 2003 09:38:31 -0800
Message-ID: <24204a6.0312310938.70ae304c@posting.google.com>

Hi,

I'm attempting to come up with a SQL script that calculates disk space usage with columns for Total, Free, Used, %Free & %Used. I think I've found several scripts that I can piece together into one script that will do what I'm looking for. However, being quite new to SQL scripts, I need to understand several areas of these scripts. Here is a sample of one of the scripts:

select df.tablespace_name tablespace,

       df.bytes/(1024*1024) tot_ts_size,
       sum(fs.bytes)/(1024*1024) free_ts_size,
       df.bytes/(1024*1024)-(fs.bytes)/(1024*1024) used_ts_size,
       round(sum(fs.bytes)*100/df.bytes) ts_pct,
       round((df.bytes-sum(fs.bytes))*100/df.bytes) ts_pct1
from dba_free_space fs, (select tablespace_name, sum(bytes) bytes
                                from dba_data_files
                                group by tablespace_name ) df

where fs.tablespace_name = df.tablespace_name group by df.tablespace_name, df.bytes

I know that "bytes" and "tablespace_name" are columns in the
"dba_free_space" and "dba_data_files" System tables, but I don't know
what the "df." and "fs." in the "df.tablespace_name", "df.bytes" &
"fs.bytes" columns mean, along with the "df" and "fs" in the FROM
clause. Any ideas?

Thanks, Received on Wed Dec 31 2003 - 11:38:31 CST