How can I retrieve the content of a BLOB data in Oracle?

To query BLOB data content in an Oracle database, you can use the following steps:

1. You can use the SELECT statement to choose the table and column that contain BLOB data. For example, if there is a table named “blob_table” with a BLOB column named “blob_column”, you can execute the following query:

SELECT blob_column FROM blob_table WHERE ...

1. In the query results, BLOB data is displayed in hexadecimal format. To view BLOB data in a readable binary or text format, you can use the subprograms in the DBMS_LOB package provided by Oracle.
2. Convert BLOB data into readable binary format using the DBMS_LOB.SUBSTR function.

SELECT DBMS_LOB.SUBSTR(blob_column, 4000, 1) FROM blob_table WHERE ...

In the example provided above, the first parameter is a BLOB column, the second parameter is the number of bytes to return, and the third parameter is the starting position.

1. Use the DBMS_LOB.GETLENGTH function to retrieve the length of BLOB data.

SELECT DBMS_LOB.GETLENGTH(blob_column) FROM blob_table WHERE ...

Note: Querying BLOB data may result in performance issues, especially when dealing with large BLOB data. Consider using paging queries or limiting the number of bytes returned to reduce the query overhead.