Read Oracle BLOB: Step-by-Step Guide

In Oracle database, you can use either PL/SQL language or SQL queries to read the value of a BLOB field.

1. Declare a variable to store the value of the BLOB field.
2. Use the SELECT INTO statement to assign the value of the BLOB field to a variable.
3. Utilize subprograms from the DBMS_LOB package to handle BLOB values, such as using the GETLENGTH function to retrieve the length of the BLOB and using the READ function to read the content of the BLOB.

Here is a sample code:

DECLARE
   my_blob BLOB;
   my_blob_length INTEGER;
   my_blob_content VARCHAR2(32767);
BEGIN
   SELECT blob_column INTO my_blob FROM my_table WHERE id = 1;
   
   my_blob_length := DBMS_LOB.GETLENGTH(my_blob);
   DBMS_OUTPUT.PUT_LINE('Blob Length: ' || my_blob_length);
   
   DBMS_LOB.READ(my_blob, my_blob_length, 1, my_blob_content);
   DBMS_OUTPUT.PUT_LINE('Blob Content: ' || my_blob_content);
END;
/

1. Retrieve the value of a BLOB field using the SELECT statement and enclose it in an appropriate function, such as TO_BLOB or UTL_RAW.CAST_TO_RAW.
2. You can utilize subprograms in the DBMS_LOB package to handle BLOB values, such as using the DBMS_LOB.GETLENGTH function to retrieve the length of a BLOB and the DBMS_LOB.READ function to read the content of a BLOB.

Here is a sample code:

SELECT DBMS_LOB.GETLENGTH(blob_column) AS blob_length,
       UTL_RAW.CAST_TO_VARCHAR2(DBMS_LOB.SUBSTR(blob_column, DBMS_LOB.GETLENGTH(blob_column), 1)) AS blob_content
FROM my_table
WHERE id = 1;

You can retrieve the value of a BLOB field using either PL/SQL or SQL queries. The specific method to use depends on your requirements and environment.