Using output redirection

Output redirection can be used to export query results.

You can redirect the output of any command to a file or device by putting the ># redirection symbol anywhere on the command. The redirection symbol must be followed by a file name. (In a command file, the file name is then followed by the semicolon used as statement terminator.) The file is placed relative to the directory where DBISQL was started.

In this example, output is redirected to the file empfile:

SELECT *
FROM employee
># empfile

Do not enclose the file name in quotation marks.

Output redirection is most useful on the SELECT statement. Use the OUTPUT_FORMAT option to control the format of the output file and the OUTPUT_LENGTH option to control truncation. For example, the following commands set the format to ASCII text and does not truncate column contents:

SET OPTION OUTPUT_FORMAT = ‘text’
SET OPTION OUTPUT_LENGTH = 0

Use two > characters in a redirection symbol instead of one (for example, >>#), to append the output to the specified file instead of replacing the contents of the file. Headings are included in the output from the SELECT statement if the output starts at the beginning of the specified file and the output format supports headings.

The >& redirection symbol redirects all output including error messages and statistics for the command on which it appears. For example:

SELECT *
FROM employee 
>& empfile

Do not enclose the file name in quotation marks.

This example outputs the SELECT statement to the file empfile, followed by the output from the SELECT statement and some statistics pertaining to the command.

The >& redirection method is useful for getting a log of what happens during a READ command. The statistics and errors of each command are written following the command in the redirected output file.

The most common reason to extract data is for use in other software products. The other software package may not understand NULL values, however.

The DBISQL option NULLS allows you to choose how NULL values are output. Alternatively, you can use the IFNULL function to output a specific value whenever there is a NULL value.