Detailed explanation of the difference between Blob and Clob in Oracle database and its usage scenarios

Title: Detailed explanation of the difference between Blob and Clob in Oracle database and usage scenarios

In Oracle database, Blob and Clob are two types of big data used to store data fields. Blob stands for Binary Large Object, which is usually used to store binary data, such as pictures, audio, video, etc.; while Clob stands for Character Large Object, which is used to store text data.

1. The difference between Blob and Clob

1. Storage type:

   • Blob: stores binary data and saves it in binary form in the database .
   • Clob: Stores text data and saves it in character form in the database.

2. Maximum storage capacity:

   • Blob: can store up to 4GB of binary data.
   • Clob: Can store up to 4GB of text data.

3. Character set:

   • Blob: Not affected by the database character set, it stores original binary data.
   • Clob: Affected by the database character set, text data is stored.

2. Usage scenarios of Blob and Clob

1. Usage scenarios of Blob:

   • Storage Image, audio, video and other binary files.
   • Storage binary data such as compressed files and backup files.
   • Back up large amounts of binary data in the database.

2. Clob usage scenarios:

   • Storage large pieces of text data, such as article content, log information, etc.
   • Storage text format data such as HTML code, XML data, etc.
   • Store data that requires text processing in the database, such as full-text search.

3. Examples of using Blob and Clob

1. Create a table containing Blob and Clob fields:

CREATE TABLE large_data (
    id NUMBER PRIMARY KEY,
    binary_data BLOB,
    text_data CLOB
);

2. Insert Blob and Clob data:

INSERT INTO large_data (id, binary_data, text_data) VALUES (1, EMPTY_BLOB(), EMPTY_CLOB());

DECLARE
    v_blob_position INTEGER;
    v_clob_position INTEGER;
BEGIN
    SELECT id, binary_data, text_data INTO v_blob_position, v_clob_position FROM large_data WHERE id = 1 FOR UPDATE;

    DBMS_LOB.WRITE(v_blob_position, 5, 1, '12345');
    DBMS_LOB.WRITE(v_clob_position, 5, 1, 'ABCDE');

    COMMIT;
END;

3. Query Blob and Clob data:

SELECT id, DBMS_LOB.SUBSTR(binary_data, 5, 1) AS binary_data,
       DBMS_LOB.SUBSTR(text_data, 5, 1) AS text_data
FROM large_data WHERE id = 1;

Through the above example, we can see how to create a Tables of Blob and Clob fields, inserting Blob and Clob data, and querying Blob and Clob data. Blob and Clob have different storage types and usage scenarios in Oracle database, which can meet application scenarios with different data storage requirements. In actual development, developers can choose the appropriate storage type to store big data type data according to specific needs.

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