Conversions

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Implicit Conversions

DuneSQL will implicitly convert numeric and character values to the correct type if such a conversion is possible.
DuneSQL will not convert implicitly 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 using the cast function.

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Implicit Casting with numeric types

DuneSQL has added support for implicit casts when performing operations with INT256 and UINT256 and other numeric types like INTEGER, BIGINTEGER, DECIMAL, or DOUBLE. This allows you to use INT256 and UINT256 without adding casts explicitly.

Whenever DuneSQL needs to find a common type for INT256 or UINT256 and another numeric type, it will generally go towards the bigger type.
We consider INT256 to be bigger than UINT256. In some cases, this might lead to an overflow error when trying to include UINT256 and INT256 values into the same expression.

TINYINT, SMALLINT, INTEGER, BIGINT, and DECIMAL type with zero scale, like DECIMAL(2,0) will be converted to INT256 or UINT256. Please note that some conversions to UINT256 will fail, since this type cannot hold negative values.

For operations involving INT256 or UINT256 and DECIMAL type with non-zero scale, like DECIMAL(2,1), the result type is DOUBLE. Also, for operations involving INT256 or UINT256 and REAL or DOUBLE types, the result type is DOUBLE. Please note that DOUBLE is an approximate numeric type and hence the conversion might lose some precision. You can use explicit cast to override DuneSQL conversion rules.

With implicit conversion, this arithmetic expression:

SELECT 2 * UINT256 '1';

will be equivalent to:

SELECT CAST(2 AS UINT256) * UINT256 '1';

Similarly, this comparison:

SELECT INT256 '1' > 0;

will be equivalent to:

SELECT INT256 '1' > CAST(0 AS INT256);

DuneSQL uses implicit conversions in many other contexts. Here are some examples:

SELECT COALESCE(1, INT256 '2');
-- will resolve to INT256

SELECT CASE 
    WHEN false THEN BIGINT '0' 
    WHEN false THEN INT256 '1' 
    WHEN true THEN UINT256 '2' 
END;
-- will resolve to INT256

SELECT * FROM (
    (VALUES TINYINT '0') 
    UNION 
    (VALUES INT256 '1') 
    UNION 
    (VALUES DOUBLE '2'));
-- will resolve to DOUBLE

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Conversion functions

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cast()

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.

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try_cast()

try_cast(value AS type) → type

Like cast, but returns null if the cast fails.

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Formatting

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format()

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'

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format_number()

format_number(number) → varchar Returns a formatted string using a unit symbol:

SELECT format_number(123456); — ‘123K’ SELECT format_number(1000000); — ‘1M’

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Miscellaneous

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typeof()

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