15.4. Conversion Functions

Presto will implicity 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.

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