Updating BLOB
columns
Updating a BLOB
column always replaces the entire contents.Even the BLOB
ID, the “handle” that is stored directly in the column, is changed.BLOB
s can be updated if:
-
The client application has made special provisions for this operation, using the Firebird API.In this case, the modus operandi is application-specific and outside the scope of this manual.
-
The new value is a string literal of no more than 65,533 bytes (64KB - 3).
NoteA limit, in characters, is calculated at run-time for strings that are in multi-byte character sets, to avoid overrunning the bytes limit.For example, for a UTF8 string (max. 4 bytes/character), the run-time limit is likely to be about (floor(65533/4)) = 16383 characters.
-
The source is itself a
BLOB
column or, more generally, an expression that returns aBLOB
. -
You use the
INSERT CURSOR
statement (ESQL only).