BLOB

Variable-length binary large object. BLOB columns can store binary data up to 65,535 bytes, suitable for images or other non-text files.

Syntax

BLOB[(M)]

Description

A BLOB column with a maximum length of 65,535 (2¹⁶ - 1) bytes. Each BLOB value is stored using a two-byte length prefix that indicates the number of bytes in the value.

An optional length M can be given for this type. If this is done, MariaDB creates the column as the smallest BLOB type large enough to hold values M bytes long.

BLOB values can also be used to store dynamic columns.

BLOB and TEXT columns can both be assigned a DEFAULT value.

Indexing

On a column that uses the BLOB data type, setting a unique index is now possible.

Note

In previous releases, setting a unique index on a column that uses the BLOB data type was not possible. Index would only guarantee the uniqueness of a fixed number of characters.

Oracle Mode

In Oracle mode, BLOB is a synonym for LONGBLOB.

EXAMPLES

BLOB

Example of BLOB:

CREATE TABLE blob_example (
   description VARCHAR(20),
   example BLOB
) DEFAULT CHARSET=latin1; -- One byte per char makes the examples clearer

INSERT INTO blob_example VALUES
   ('Normal foo', 'foo'),
   ('Trailing spaces foo', 'foo      '),
   ('NULLed', NULL),
   ('Empty', ''),
   ('Maximum', RPAD('', 65535, CHAR(7)));

SELECT description, LENGTH(example) AS length
   FROM blob_example;

+---------------------+--------+
| description         | length |
+---------------------+--------+
| Normal foo          |      3 |
| Trailing spaces foo |      9 |
| NULLed              |   NULL |
| Empty               |      0 |
| Maximum             |  65535 |
+---------------------+--------+

Data Too Long

When SQL_MODE is strict (the default) a value is considered "too long" when its length exceeds the size of the data type, and an error is generated.

Example of data too long behavior for BLOB:

TRUNCATE blob_example;

INSERT INTO blob_example VALUES
   ('Overflow', RPAD('', 65536, CHAR(7)));

ERROR 1406 (22001): Data too long for column 'example' at row 1

See Also

• BLOB and TEXT Data Types

• Data Type Storage Requirements

• Oracle mode

_{This page is licensed: GPLv2, originally from fill_help_tables.sql}