Updated May 31, 2023
Introduction to sqlplus spool
The following article provides an outline for sqlplus spool. Information technology has a unique form of multi-programming to support the copy of information between different devices. Such a process is called spooling. It is used to interact between peripheral devices like printers, hardware devices, and computer applications in recent systems. Buffering and queuing together constitute a spooling process. It mostly happens in the client’s place and not at the server end. The user has the option to spool only to a specific directory. The .lst file is developed on the machine by the Developer and doesn’t happen on the database where it is linked to its residing place. In this article, we can discuss usage, examples, and a few commands of spooling.
SQLplus spool Usage
SQLplus is developed by Oracle, which enables the user to interact, enter and run the SQL commands on the SQL blocks. The spool command is used in SQLplus to instruct the output of the query to the side flat file of the server. It is due to the spool command that interacts with the layer of OS, and it is implemented in shell scripts of Oracle. To run the spool file, the user has to run a script and should click on F5 to execute the spool file as a script. Then the CSV file is created on the allocated path. A spooled file stores the output data till it gets printed and also collects the information from a device till a device or program can work on the data. The program works on the spooled as it is copied or read from an actual device.
By using a spool, CSV files are exported as query results. In a table WHERE command is used to run the spool, the user must execute it as a script. The user works on the preference settings to instruct the output of the query to the file. It denotes the file name to which the user wants to spool. The SPOOL comes with the file name and displays the output to the named file. If the user doesn’t wish to give any extension, the spool itself chooses its default extension like LIS or LST. There are many options for the user to compose a conditional message to the spool file of SQLplus.
What is a spool file?
Spooling is a process used to access information from devices that are at different rates. The buffer of the spool offers a holding station where the information can be placed at rest when the device is slow, like cache clearance, waiting for a print job, etc. Then, when the device is ready to manage its work, it can process the next batch of data from the buffer pool. So in simple, the spooled file stores the data until it gets processed, gathers the data from the program or devices, and holds it in the waiting area until it gets processed. So the compiled program of spool acts if it was writing or reading to an original component.
SQLplus spool example
When the spool command becomes unavailable in the browser version of SQLplus, then iSQLplus is used to execute the files and has the option to edit the required preference setting to the direct output of the file. So when the settings are ready, the user has to instruct the spool statement in SQLplus to an output of the file. So when the Spool changes to an active state, the output of the query can be stored to the SQLplus to the allotted file.
The command to enter in the spool is spool file_path. It skipped ahead once the query was given, and also, it is required to stop the spool because the spool terminates the output of the file off command. Once the configuration is done and the spool is executed, then it should get inserted in the query. As an example, if we are printing the available courses from the website, they should be given as
SELECT Coursename, Duration FROM Educba;
It is mandatory to put a semi-colon, to end the query statement and the above-given spool off command. So this is the way to generate a new file with the output of the query by SQLplus.
Instead of entering every line manually, it is recommended to give all the specific values into a new scripting file, and then the user can run it by using a single command in sqlplus
Develop a new script file using the Edit statement.
Now give the complete script command into the new file and store it. The entire content of the file should be as given in the example.
SET column, SET headsep SET linesize SET fontsize SET trimspool SET numwidth Spool educba.csv SELECT Coursename, Duration FROM Educba; Spool off
To run the script, the user can inset @symbol provided by the name of the file.
@file_name, the executed script should be in .csv file SQLplus Spool on/off
Spool on and spool off can also be done in different methods. Note the output session of the MaxL shell and transfer the standard output error messages, informational messages, and warning messages executed by the MaxL statement to a file. If a FILE-NAME doesn’t exist, it is created already, and if the filename is present already, it can be again written. If the path of the directory is not specified for any file name, then the filename is already created in the directory. By using the spool command, the user cannot create any directories. The logging of the message starts with spool on and stops with spool off. The operating system has three channels for input and output. It is standard input- STDIN, standard output-STDOUT, and standard error channel-STDERR. Most operating systems offer the option to command-line to re-direct the data produced by applications based on the above channels where the data is piped. The standard output can be saved from the error output separately.
Hence these are some of the basic activities using the spool command, and it can be configured accordingly as per user preference. The process of the spool is used at many locations as it is time-consuming.
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