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) -> 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¶

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