### 11.3.4 The BLOB and TEXT Types

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 A `BLOB` is a binary large object that can hold a variable amount of data. The four `BLOB` types are `TINYBLOB`, `BLOB`, `MEDIUMBLOB`, and `LONGBLOB`. These differ only in the maximum length of the values they can hold. The four `TEXT` types are `TINYTEXT`, `TEXT`, `MEDIUMTEXT`, and `LONGTEXT`. These correspond to the four `BLOB` types and have the same maximum lengths and storage requirements. See [Section 11.7, “Data Type Storage Requirements”](storage-requirements.html).

`BLOB` values are treated as binary strings (byte strings). They have the `binary` character set and collation, and comparison and sorting are based on the numeric values of the bytes in column values. `TEXT` values are treated as nonbinary strings (character strings). They have a character set other than `binary`, and values are sorted and compared based on the collation of the character set.

 If strict SQL mode is not enabled and you assign a value to a `BLOB` or `TEXT` column that exceeds the column's maximum length, the value is truncated to fit and a warning is generated. For truncation of nonspace characters, you can cause an error to occur (rather than a warning) and suppress insertion of the value by using strict SQL mode. See [Section 5.1.11, “Server SQL Modes”](sql-mode.html).

 Truncation of excess trailing spaces from values to be inserted into [`TEXT`](blob.html) columns always generates a warning, regardless of the SQL mode.

 For `TEXT` and `BLOB` columns, there is no padding on insert and no bytes are stripped on select.

 If a `TEXT` column is indexed, index entry comparisons are space-padded at the end. This means that, if the index requires unique values, duplicate-key errors occur for values that differ only in the number of trailing spaces. For example, if a table contains `'a'`, an attempt to store `'a '` causes a duplicate-key error. This is not true for `BLOB` columns.

 In most respects, you can regard a `BLOB` column as a [`VARBINARY`](binary-varbinary.html) column that can be as large as you like. Similarly, you can regard a `TEXT` column as a [`VARCHAR`](char.html) column. `BLOB` and `TEXT` differ from [`VARBINARY`](binary-varbinary.html) and [`VARCHAR`](char.html) in the following ways:

* For indexes on `BLOB` and `TEXT` columns, you must specify an index prefix length. For [`CHAR`](char.html) and [`VARCHAR`](char.html), a prefix length is optional. See [Section 8.3.5, “Column Indexes”](column-indexes.html).

* []() []() []() `BLOB` and `TEXT` columns cannot have `DEFAULT` values.

 If you use the `BINARY` attribute with a `TEXT` data type, the column is assigned the binary (`_bin`) collation of the column character set.

`LONG` and `LONG VARCHAR` map to the `MEDIUMTEXT` data type. This is a compatibility feature.

 MySQL Connector/ODBC defines `BLOB` values as `LONGVARBINARY` and `TEXT` values as `LONGVARCHAR`.

 Because `BLOB` and `TEXT` values can be extremely long, you might encounter some constraints in using them:

* Only the first [`max_sort_length`](server-system-variables.html#sysvar_max_sort_length) bytes of the column are used when sorting. The default value of [`max_sort_length`](server-system-variables.html#sysvar_max_sort_length) is 1024. You can make more bytes significant in sorting or grouping by increasing the value of [`max_sort_length`](server-system-variables.html#sysvar_max_sort_length) at server startup or runtime. Any client can change the value of its session [`max_sort_length`](server-system-variables.html#sysvar_max_sort_length) variable:

  ```
  mysql> SET max_sort_length = 2000;
  mysql> SELECT id, comment FROM t
      -> ORDER BY comment;
  ```

* Instances of `BLOB` or `TEXT` columns in the result of a query that is processed using a temporary table causes the server to use a table on disk rather than in memory because the `MEMORY` storage engine does not support those data types (see [Section 8.4.4, “Internal Temporary Table Use in MySQL”](internal-temporary-tables.html)). Use of disk incurs a performance penalty, so include `BLOB` or `TEXT` columns in the query result only if they are really needed. For example, avoid using [`SELECT *`](select.html), which selects all columns.

* The maximum size of a `BLOB` or `TEXT` object is determined by its type, but the largest value you actually can transmit between the client and server is determined by the amount of available memory and the size of the communications buffers. You can change the message buffer size by changing the value of the [`max_allowed_packet`](server-system-variables.html#sysvar_max_allowed_packet) variable, but you must do so for both the server and your client program. For example, both [**mysql**](mysql.html) and [**mysqldump**](mysqldump.html) enable you to change the client-side [`max_allowed_packet`](server-system-variables.html#sysvar_max_allowed_packet) value. See [Section 5.1.1, “Configuring the Server”](server-configuration.html), [Section 4.5.1, “mysql — The MySQL Command-Line Client”](mysql.html), and [Section 4.5.4, “mysqldump — A Database Backup Program”](mysqldump.html). You may also want to compare the packet sizes and the size of the data objects you are storing with the storage requirements, see [Section 11.7, “Data Type Storage Requirements”](storage-requirements.html)

 Each `BLOB` or `TEXT` value is represented internally by a separately allocated object. This is in contrast to all other data types, for which storage is allocated once per column when the table is opened.

 In some cases, it may be desirable to store binary data such as media files in `BLOB` or `TEXT` columns. You may find MySQL's string handling functions useful for working with such data. See [Section 12.8, “String Functions and Operators”](string-functions.html). For security and other reasons, it is usually preferable to do so using application code rather than giving application users the [`FILE`](privileges-provided.html#priv_file) privilege. You can discuss specifics for various languages and platforms in the MySQL Forums ([http://forums.mysql.com/](http://forums.mysql.com/)).

Note

 Within the [**mysql**](mysql.html) client, binary strings display using hexadecimal notation, depending on the value of the [`--binary-as-hex`](mysql-command-options.html#option_mysql_binary-as-hex). For more information about that option, see [Section 4.5.1, “mysql — The MySQL Command-Line Client”](mysql.html).

