Oracle TO_CLOB(bfile|blob) Function

Oracle TO_CLOB(bfile|blob) is a built-in function that converts BFILE or BLOB data to the database character set and returns the data as a CLOB value.

Oracle `TO_CLOB(bfile|blob)` Syntax

Here is the syntax of the Oracle TO_CLOB(bfile|blob) function:

TO_CLOB( { bfile | blob } [, csid] [, mime_type] )

Parameters

bfile | blob: Required. The data to be converted.
csid: Optional. It specifies the character set ID of the BFILE or BLOB data. If the character set of the BFILE or BLOB data is the database character set, you can specify a value of 0 for csid, or completely omit the csid parameter.
mime_type: Optional. It specifies the MIME type to be set on the CLOB value returned by this function. If mime_type is omitted, no MIME type is set on the returned CLOB value.

Return Value

The Oracle TO_CLOB(bfile|blob) function converts BFILE or BLOB data to the database character set and returns the data as a CLOB value.

If any of the parameters are NULL, TO_CLOB(bfile|blob) returns NULL.

Oracle `TO_CLOB(bfile|blob)` Examples

Here are some examples that demonstrate the usage of the Oracle TO_CLOB(bfile|blob) function.

Basic Usage

Here is a hypothetical example that returns a CLOB value for the docu column in table media_tab using character set ID 873. It sets the MIME type of the resulting CLOB to text/xml.

SELECT TO_CLOB(docu, 873, 'text/xml')
FROM media_tab;

NULL Parameters

If any of the parameters are NULL, TO_CLOB() returns NULL.

SET NULL 'NULL';
SELECT
  TO_CLOB(NULL)
FROM dual;

输出：

TO_CLOB(NULL)
________________
NULL

In this example, we use the statement SET NULL 'NULL'; to display NULL values as the string 'NULL'.

Conclusion