Binary Input and Output¶
Snowflake supports three binary formats or encoding schemes: hex, base64, and UTF-8.
In this Topic:
Overview of Supported Binary Formats¶
The “hex” format refers to the hexadecimal, or base 16, system. In this format, each byte is represented by two characters (digits and letters from
F). When using hex to perform conversion:
|Binary||String||hex uses uppercase letters.|
|String||Binary||hex is case-insensitive.|
Hex is the default binary format.
The base64 format refers to the base 64 encoding scheme defined in RFC 4648. With this format, each group of 3 bytes is represented by 4 characters (digits, letters,
/, with the
= character for padding). When using base64 to performing conversion:
|Binary||String||base64 does not insert any whitespace or line breaks.|
|String||Binary||base64 ignores all whitespace and line breaks.|
The UTF-8 format refers to the UTF-8 character encoding for Unicode. Unlike hex and base64, which are binary-to-text encodings, UTF-8 is a text-to-binary encoding. This means that conversion from string to binary always succeeds, but conversion from binary to string can fail.
This format is convenient for performing one-to-one conversion between binary and string, for reinterpreting the underlying data as one type or the other rather than actually encoding and decoding.
Session Parameters for Binary Values¶
There are two session parameters that determine how binary values are passed into and out of Snowflake:
- Performing conversion to binary in the one-argument version of TO_CHAR , TO_VARCHAR.
- Loading data into Snowflake (if no file format option is specified; see below for details).
The parameter can be set to HEX, BASE64, or UTF-8 (UTF8 is also allowed). The parameter values are case-insensitive. The default is HEX.
- Displaying binary result sets.
- Performing conversion to string in the one-argument version of TO_BINARY.
- Unloading data from Snowflake (if no file format option is specified; see below for details).
The parameter can be set to HEX or BASE64. The parameter values are case-insensitive. The default is HEX.
Because conversion from binary to string may fail with the UTF-8 format, BINARY_OUTPUT_FORMAT can not be set to UTF-8. To use UTF-8 for conversion in this situation, use the two-argument version of TO_CHAR , TO_VARCHAR.
The parameters can be set at the account, user, and session levels. Execute the SHOW PARAMETERS command to view the current parameter settings that apply to all operations in the current session.
File Format Option for Loading/Unloading Binary Values¶
Separate from the binary input and output session parameters, Snowflake provides the BINARY_FORMAT file format option, which can be used to explicitly control binary formatting when loading data into or unloading data from Snowflake tables.
This option can be set to HEX, BASE64, or UTF-8 (values are case-insensitive). The option affects both data loading and unloading and, similar to other file format options, can be specified in a number of ways:
- In a named file format, which can then be referenced in a named stage or directly in a COPY command.
- In a named stage, which can then be referenced directly in a COPY command.
- Directly in a COPY command.
When used for data loading, BINARY_FORMAT specifies the format of binary values in your staged data files. This option overrides any value set for the BINARY_INPUT_FORMAT parameter in the session (see Session Parameters for Binary Values above).
If the option is set to HEX or BASE64, data loading may fail if the strings in the staged data file are not valid hex or base64. In this case, Snowflake returns an error and then performs the action specified for the ON_ERROR copy option.
When used in data unloading, the BINARY_FORMAT option specifies the format applied to binary values unloaded to the files in the specified stage. This option overrides any value set for the BINARY_OUTPUT_FORMAT parameter in the session (see Session Parameters for Binary Values above).
If the option is set to UTF-8, data unloading may fail if any binary values in the table contain invalid UTF-8. In this case, Snowflake returns an error.