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

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.

try_cast(value AS type) type

Like 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.

Data Size

The parse_presto_data_size function supports the following units:

Unit

Description

Value

B

Bytes

1

kB

Kilobytes

1024

MB

Megabytes

10242

GB

Gigabytes

10243

TB

Terabytes

10244

PB

Petabytes

10245

EB

Exabytes

10246

ZB

Zettabytes

10247

YB

Yottabytes

10248

parse_presto_data_size(string)

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

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