CHAPTER 5: Empress Variables

The Empress Query Language maintains a list of character-string variables. Variables may be printed, new ones added, old ones removed, and their values changed and used.

Variables are of three types:

1. Alphanumeric variables, the names of which begin with a letter and contain letters and numbers.

2. Numeric variables, names of which range from "1" to "99".

3. System variables, a set of variables used for specific purposes by Empress.

Alphanumeric and numeric variables are described under the SET command in the Empress SQL: Reference.

The contents of a variable are referred to by placing a dollar sign ($) in front of the name. Where it is necessary to enter extra characters after a variable name, the variable name must be surrounded by braces, thus: ${VARIABLE}. For example, suppose you have a file of data to go into the personnel table called personnel_file. If you wish to use the variable p to shorten typing as personnel when inserting data into personnel, and use:

   INSERT INTO $p FROM '$p_file';

you will get an error message because the variable p_file is not defined. Instead, you should type:

   INSERT INTO $p FROM '${p}_file';

in order to obtain the desired command: "INSERT INTO personnel FROM personnel_file;".

To prevent a dollar sign ($) from causing variable expansion, it must be doubled; i.e., $$p evaluates to the string $p. This applies anywhere in a string and not only for the beginning of each "word". Note that both the character used to obtain the value of a variable and the characters used as delimiters may be changed by setting the Empress system variable MSQLVARCHARS. To have & instead of $ and square brackets instead of braces, use:

   SET MSQLVARCHARS TO &[];

Variables are set with the SET command and removed with the UNSET command. The value of variables is shown with the SHOW command.

Empress has a number of system variables which determine system defaults, such as the line continuation character, number of retrieves when trying to access locked tables, formatting of SELECT command output, and so on. These variables acquire values in one of two ways: they are set by Query Language commands during a work-session, or they are inherited from the operating system.

To set a system variable from the Query Language, use a command of the form:

   SET variable TO value;

where variable is the name of the system variable (which must all be in uppercase only), and value is its value. The value must be enclosed in quotes if it contains blanks, tabs, periods, colons, semicolons, slashes, or new lines.

If a variable is set via a Query Language command, its value lasts only for the current work-session, and it must be re-set if you stop Empress. If a variable is set in the operating system, its value lasts as long as you are logged on to the operating system, and thus may last over several Empress work-sessions. Variables set in the operating system are also available to Empress 4GL and Empress Report Writer.

For UNIX:

To set a variable from the UNIX shell use a setenv command in the C shell, or export command in the Bourne shell.

For example, to set the variable MSEDITOR to "/usr/ucb/vi", the C shell command is:

   setenv MSEDITOR /usr/ucb/vi

and the Bourne shell commands are:

   MSEDITOR=/usr/ucb/vi/
   export MSEDITOR

If you wish to have permanent lists of Empress system variables which will be in force for every work-session, you may either:

1. Place these in a UNIX file and set the variables from this file whenever you invoke Empress.

2. Set the variables in your .login (C shell) or .profile (Bourne shell) files. Instructions for doing this may be obtained from the UNIX system documentation.

For Windows NT:

To set a variable from the Windows NT environment, use the Set Environment command. For example, to set the variable MSVALSEP to "|", the Windows NT command is:

   set MSVALSEP=|

You may also want to set some Empress system variables permanently. One way of doing this is to put the Empress system variables in your user environment variable list. Consult your system documentation for details.

A list of the system variables follows with a brief description of each.

Table 5-1: Path Specific System Variables

Table 5-2: General Purpose System Variables

Table 5-3: Transaction Specific System Variables

Table 5-4: Locking Specific System Variables

Table 5-5: Query Language Specific System Variables

Table 5-6: Select Formatting Specific System Variables

Table 5-7: Operating System Specific System Variables

Table 5-8: Empress Report Writer Specific System Variables