Conversion functions

Примечание

Ниже приведена оригинальная документация Trino. Скоро мы ее переведем на русский язык и дополним полезными примерами.

Trino will implicitly convert numeric and character values to the correct type if such a conversion is possible. Trino 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.

Formatting

format(format, args...) → varchar

Returns a formatted string using the specified format string and arguments:

SELECT format('%s%%', 123);
-- '123%'

SELECT format('%.5f', pi());
-- '3.14159'

SELECT format('%03d', 8);
-- '008'

SELECT format('%,.2f', 1234567.89);
-- '1,234,567.89'

SELECT format('%-7s,%7s', 'hello', 'world');
-- 'hello  ,  world'

SELECT format('%2$s %3$s %1$s', 'a', 'b', 'c');
-- 'b c a'

SELECT format('%1$tA, %1$tB %1$te, %1$tY', date '2006-07-04');
-- 'Tuesday, July 4, 2006'

format_number(number) → varchar

Returns a formatted string using a unit symbol:

SELECT format_number(123456); -- '123K'
SELECT format_number(1000000); -- '1M'

Data size

The parse_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_data_size(string)

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

SELECT parse_data_size('1B'); -- 1
SELECT parse_data_size('1kB'); -- 1024
SELECT parse_data_size('1MB'); -- 1048576
SELECT parse_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