==================== Conversion Functions

Presto will implicitly convert numeric and character values to the correct type if such a conversion is possible. Presto will not convert between character and numeric types. For example, a query that expects a varchar will not automatically convert a bigint value to an equivalent varchar.

When necessary, values can be explicitly cast to a particular type.

Conversion Functions

.. function:: cast(value AS type) -> type

Explicitly cast a value as a type. This can be used to cast a
varchar to a numeric value type and vice versa.

.. function:: try_cast(value AS type) -> type

Like :func:`!cast`, but returns null if the cast fails.

.. note::

When casting strings to integer types such as ``TINYINT``, 
``SMALLINT``, ``INTEGER``, or ``BIGINT``, leading 
and trailing spaces in the string are allowed. See  `Integer <../language/types.html#integer>`_.

Data Size

The parse_presto_data_size function supports the following units:

======= ============= ============== Unit Description Value ======= ============= ============== B Bytes 1 kB Kilobytes 1024 MB Megabytes 1024\ :sup:2 GB Gigabytes 1024\ :sup:3 TB Terabytes 1024\ :sup:4 PB Petabytes 1024\ :sup:5 EB Exabytes 1024\ :sup:6 ZB Zettabytes 1024\ :sup:7 YB Yottabytes 1024\ :sup:8 ======= ============= ==============

.. function:: parse_presto_data_size(string) -> decimal(38)

Parses ``string`` of format ``value unit`` into a number, where
``value`` is the fractional number of ``unit`` values::

    SELECT parse_presto_data_size('1B'); -- 1
    SELECT parse_presto_data_size('1kB'); -- 1024
    SELECT parse_presto_data_size('1MB'); -- 1048576
    SELECT parse_presto_data_size('2.3MB'); -- 2411724

Miscellaneous

.. function:: typeof(expr) -> varchar

Returns the name of the type of the provided expression::

    SELECT typeof(123); -- integer
    SELECT typeof('cat'); -- varchar(3)
    SELECT typeof(cos(2) + 1.5); -- double