String Comparisons
You can use the equals (=) and does not equal ('=) operators to compare two strings. String equality comparisons are case-sensitive. Exercise caution when using these operators to compare a string to a number, because this comparison is a string comparison, not a numeric comparison. Therefore only a string containing a number in canonical form is equal to its corresponding number. ("-0" is not a canonical number.) This is shown in the following example:
WRITE "Fred" = "Fred",! // TRUE
WRITE "Fred" = "FRED",! // FALSE
WRITE "-7" = -007.0,! // TRUE
WRITE "-007.0" = -7,! // FALSE
WRITE "0" = -0,! // TRUE
WRITE "-0" = 0,! // FALSE
WRITE "-0" = -0,! // FALSE
The <, >, <=, or >= operators cannot be used to perform a string comparison. These operators treat strings as numbers and always perform a numeric comparison. Any non-numeric string is assigned a numeric value of 0 when compared using these operators.
Lettercase and String Comparisons
String equality comparisons are case-sensitive. You can use the $ZCONVERT function to convert the letters in the strings to be compared to all uppercase letters or all lowercase letters. Non-letter characters are unchanged.
A few letters only have a lowercase letter form. For example, the German eszett ($CHAR(223)) is only defined as a lowercase letter. Converting it to an uppercase letter results in the same lowercase letter. For this reason, when converting alphanumeric strings to a single letter case it is always preferable to convert to lowercase.
