BLOB Columns
From InterBase
Go Up to Defining BLOB Data Types
You define BLOB
columns in database tables just as you do non-BLOB
columns. For example, the following statement creates a table with a BLOB
column:
CREATE TABLE PROJECT
(PROJ_ID PROJNO NOT NULL,
PROJ_NAME VARCHAR(20) NOT NULL UNIQUE,
PROJ_DESC BLOB,
TEAM_LEADER EMPNO,
PRODUCT PRODTYPE,
. . .);
Rather than storing BLOB
data directly, a BLOB
column stores a BLOB ID
. A BLOB ID
is a unique numeric value that references BLOB
data. The BLOB
data is stored elsewhere in the database, in a series of BLOB
segments, which are units of BLOB data that are read and written in chunks. InterBase writes data to a BLOB
one segment at a time. Similarly, it reads a BLOB
one segment at a time.
The following diagram shows the relationship between a BLOB column containing a BLOB ID
, and the BLOB
data referenced by the BLOB ID
: