Comparison of storage principles and applicable scenarios of Blob and Clob in Oracle

Comparison of storage principles and applicable scenarios of Blob and Clob in Oracle

In Oracle database, Blob and Clob are two commonly used data types, used to store large Capacity of binary data (Blob) and character data (Clob). This article will introduce the storage principles of Blob and Clob respectively, as well as their applicability in different scenarios, and deepen understanding through specific code examples.

Blob storage principle

Blob is the abbreviation of Binary Large Object, which is used to store binary data, such as pictures, audio, video, etc. Blob type data is stored in binary format in the database and is usually used to store large files or binary data.

The storage principle of Blob is to store binary data in the database in the form of byte stream. The database will dynamically allocate storage space based on the size of the Blob data to ensure data integrity and security.

Clob storage principle

Clob is the abbreviation of Character Large Object, which is used to store large amounts of character data, such as text, code, etc. Clob type data is stored in character format in the database and is usually used to store text data.

The storage principle of Clob is to store character data in the database in the form of a character stream. The database will dynamically allocate storage space according to the size of the Clob data, and encode and store the data according to the character set.

Comparison of applicable scenarios between Blob and Clob

1. Applicable scenarios for Blob:

   • Storage large files (such as pictures, audio, videos, etc.);
   • Storage binary data, such as compressed packages, serialized objects, etc.;
   • Scenarios that require binary operations or processing of data.

2. Clob applicable scenarios:

   • Storage large text content, such as articles, logs, codes, etc.;
   • Storage character data , such as XML, JSON and other format data;
   • Scenarios that require text manipulation or processing of data.

Code examples for Blob and Clob

Blob example:

CREATE TABLE Blob_Table (
    id NUMBER PRIMARY KEY,
    image_data BLOB
);

INSERT INTO Blob_Table (id, image_data) VALUES (1, EMPTY_BLOB());

DECLARE
    l_blob BLOB;
BEGIN
    SELECT image_data INTO l_blob FROM Blob_Table WHERE id = 1 FOR UPDATE;
    DBMS_LOB.WRITE(l_blob, DBMS_LOB.GETLENGTH(l_blob), 1, utl_raw.cast_to_raw('Insert Blob Data Here'));
    COMMIT;
END;
/

Clob example:

CREATE TABLE Clob_Table (
    id NUMBER PRIMARY KEY,
    text_data CLOB
);

INSERT INTO Clob_Table (id, text_data) VALUES (1, 'Insert Clob Data Here');

DECLARE
    l_clob CLOB;
BEGIN
    SELECT text_data INTO l_clob FROM Clob_Table WHERE id = 1 FOR UPDATE;
    l_clob := l_clob || ' Appending Clob Data Here';
    UPDATE Clob_Table SET text_data = l_clob WHERE id = 1;
    COMMIT;
END;
/

Summary

Blob and Clob are two types used to store large-capacity data in Oracle database, which are suitable for storing binary data and character data respectively. Blob stores data in binary form and is suitable for storing large files and binary data, while Clob stores data in character form and is suitable for storing large text content and character data. When using Blobs and Clobs, you need to choose the appropriate data type based on actual needs, and understand their storage principles in order to effectively operate and manage large volumes of data.

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