|expression||A string expression, which can be the name of a column, a string literal, or the result of another function, where the underlying data type can be represented as any character type (such as CHAR or VARCHAR2). expression can be a subquery.|
|length||Optional — The truncation length, specified as an integer. The initial length characters of expression are returned. If you omit length, %TRUNCATE collation is identical to %EXACT collation. You can enclose length with double parentheses to suppress literal substitution: ((length)).|
%TRUNCATE truncates expression to the specified length, then returns it in the EXACT collation sequence.
EXACT collation orders pure numeric values (values for which x=+x) in numeric order first, followed by all other characters in string collation sequence. The EXACT string collation sequence is the same as the ANSI-standard ASCII collation sequence: digits are collated before uppercase alphabetic characters and uppercase alphabetic characters are collated before lowercase alphabetic characters. Punctuation characters occur at several places in the sequence.
%TRUNCATE passes through NULLs unchanged.
%TRUNCATE is an InterSystems SQL extension and is intended for SQL lookup queries.
This function can also be invoked from ObjectScript using the TRUNCATE()Opens in a new tab method call:
WRITE $SYSTEM.SQL.Functions.TRUNCATE("This long string",9)
The following example uses %TRUNCATE to return the first four characters of Name values:
SELECT TOP 5 Name,%TRUNCATE(Name,4) AS ShortName FROM Sample.Person
The following example applies %TRUNCATE to a subquery:
SELECT TOP 5 Name, %TRUNCATE((SELECT Name FROM Sample.Company),10) AS Company FROM Sample.Person
The following example uses %TRUNCATE in the GROUP BY clause to create an alphabet list that returns the number of names that begin with each letter:
SELECT Name AS FirstLetter,COUNT(Name) AS NameCount FROM Sample.Person GROUP BY %TRUNCATE(Name,1) ORDER BY Name
The following two examples show how %TRUNCATE performs EXACT collation. The ORDER BY in the first example truncates Home_Street to two characters. Because the first two characters of a street address are almost always numbers, the Home_Street fields are ordered in the numeric sequence of their first two numbers.
SELECT Name,Home_Street FROM Sample.Person ORDER BY %TRUNCATE(Home_Street,2)
The ORDER BY in the second example truncates Home_Street to four characters. Because the fourth character of some street addresses is not a number (a blank space, for example), the Home_Street values that begin with four (or more) numbers are ordered first in numeric sequence, then the Home_Street values that contain a non-numeric character within the first four characters are ordered in string sequence:
SELECT Name,Home_Street FROM Sample.Person ORDER BY %TRUNCATE(Home_Street,4)
%EXACT collation function
%SQLSTRING collation function
%TRUNCATE collation function
Collation chapter in Using InterSystems SQL