SQLのBLOBおよびCLOBデータ型は何ですか？

BLOB stores binary data like images, audio, or PDFs as raw bytes without character encoding, while CLOB stores large text such as articles or JSON using character encoding like UTF-8 and supports string operations; 2. Both can handle up to gigabytes of data depending on the database, but performance and backup efficiency should be considered; 3. Database-specific equivalents include MySQL’s LONGBLOB and LONGTEXT, PostgreSQL’s BYTEA and TEXT, Oracle’s BLOB and CLOB, and SQL Server’s VARBINARY(MAX) and VARCHAR(MAX); 4. Use BLOB for non-text binaries and CLOB for large textual content to ensure proper data handling and scalability.

BLOB and CLOB are SQL data types used to store large amounts of data, especially when regular data types like VARCHAR or TEXT aren't sufficient. They’re part of the "Large Object" (LOB) category and are designed for different kinds of data.

1. BLOB (Binary Large Object)

BLOB is used to store binary data—data that isn't text-based and can't be interpreted as characters.

• Typical use cases:

  
  • Images (JPEG, PNG)
  • Audio or video files
  • PDFs or other documents
  • Executable files

• How it works:

  • Stores raw byte data.
  • Not interpreted by the database in terms of character encoding.
  • Can be very large—often up to gigabytes, depending on the database system.

• Example (MySQL):

  

  CREATE TABLE media (
      id INT PRIMARY KEY,
      photo BLOB
  );

⚠️ While convenient, storing files directly in BLOBs can slow down database performance and complicate backups. Often, it's better to store file paths and keep the actual files on a file system or cloud storage.

2. CLOB (Character Large Object)

CLOB is used to store large text data in a character format.

• Typical use cases:

  • Long articles or blog posts
  • JSON or XML documents
  • Logs or configuration files
  • Any large textual content

• How it works:

  • Stores text using the database’s character encoding (like UTF-8).
  • Supports standard string operations (e.g., LIKE, SUBSTRING) in many databases.
  • Handles much larger text than VARCHAR or TEXT.

• Example (Oracle):

  CREATE TABLE articles (
      id NUMBER PRIMARY KEY,
      content CLOB
  );

Key Differences

Database Support Variations

Different databases use slightly different names:

• MySQL: BLOB, LONGBLOB, TEXT, LONGTEXT
• PostgreSQL: BYTEA (for BLOB), TEXT (for CLOB-like use)
• Oracle: BLOB, CLOB, NCLOB (for national character sets)
• SQL Server: VARBINARY(MAX) (BLOB), VARCHAR(MAX) or NVARCHAR(MAX) (CLOB)

So, in short:

• Use BLOB when storing non-text files like images or binaries.
• Use CLOB when storing very large text that exceeds normal string limits.

They’re powerful but should be used carefully—especially with performance and backup considerations.

Basically, if you're dealing with large content, pick BLOB for binary and CLOB for text.

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