SQL Server 2019

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CREATE TABLE tablename(UserID varchar(100), ColumnName text)
DECLARE @ptrval BINARY(16);  
SELECT @ptrval = TEXTPTR(t.ColumnName) 
FROM tablename t
WHERE UserID = 'myID';

UPDATETEXT tablename.ColumnName @ptrval 0 NULL 'data';
Msg 7133 Level 16 State 2 Line 6
NULL textptr (text, ntext, or image pointer) passed to UPDATE TEXT function.
Msg 3621 Level 0 State 0 Line 1
The statement has been terminated.

UPDATE tablename
SET ColumnName = 'data'
WHERE UserID = 'myID';