STRING

The STRING data type is a variable-length, dynamically allocated character string data type, without limitation.

Syntax

STRING

Usage

The STRING data type is typically used to implement utility functions manipulating character string with unknown size, and in some special cases, in SQL statements.

STRING variables are initialized to NULL in functions, modules and globals.

The behavior of a STRING variable is similar to the VARCHAR data type, except that there is no theoretical size limit.

STRING variables can be initialized from string literals:

MAIN
    DEFINE s STRING
    LET s = "abcdef"
END MAIN

Variables declared with the STRING data type can be used to call STRING-type methods such as getLength() or toUpperCase(). For more details, see The STRING data type as class:

MAIN
    DEFINE s STRING
    LET s = "abc"
    DISPLAY s.toUpperCase()
END MAIN

STRING variables have significant trailing blanks (i.e. "abc " is different from "abc"). However, in comparisons, trailing blancs do not matter:

MAIN
    DEFINE s STRING
    LET s = "abc  " -- a b c + 2 white spaces
    DISPLAY "1: s.length:", s.getLength()
    DISPLAY "[", s, "]" -- displays "[abc  ]"
    DISPLAY IIF(s=="abc","Equals",NULL)
END MAIN

Unlike CHAR and VARCHAR, a STRING can hold a value of zero length without being NULL. For example, if you trim a string variable with the trim() method and if the original value is a set of blank characters, the result is an empty string. But testing the variable with the IS NULL operator will evaluate to FALSE. Using a VARCHAR with the CLIPPED operator would give a NULL string in this case:

MAIN
    DEFINE s STRING
    LET s = "     " -- 5 spaces
    LET s = s.trim()
    DISPLAY "s = [", s, "] len=", s.getLength()
    DISPLAY IIF(s IS NULL, "NULL", "not NULL")
END MAIN

outputs:

s = [] len=          0
not NULL

STRING typed variables can be used in some special cases to hold SQL character string data, when the size of the SQL data string is not known (string expressions, large strings like JSON documents). In order to store character string data stored in a database, consider using the CHAR or VARCHAR types instead of STRING.

In STRING methods, positions and length parameters (or return values) can be expressed in bytes or characters, depending on the length semantics used in programs. For more details, see Length semantics settings