Literals

Literals are the constant values you write directly in queries — numbers, strings, dates, arrays. Because FeatureQL infers types from literals, the way you write a value determines its type. 1 is a BIGINT, 1.0 is a DECIMAL, and 1e0 is a DOUBLE — three different types from three different notations.

Numeric literals

Integer size, decimal precision, and floating-point type are all controlled by how you write the number:

SELECT
    TYPEOF(TINYINT '1') AS F_TINYINT,
    TYPEOF(SMALLINT '1') AS F_SMALLINT,
    TYPEOF(MEDIUMINT '1') AS F_MEDIUMINT,
    TYPEOF(1) AS F_BIGINT,
    TYPEOF(1.123) AS F_DECIMAL,
    TYPEOF(FLOAT '1.1') AS F_FLOAT,
    TYPEOF(DOUBLE '1.1') AS F_DOUBLE,
    TYPEOF(1.1e0) AS F_DOUBLESCI,
;

The TYPEOF() results reveal the inferred types. Plain 1 defaults to BIGINT. Decimal literals like 1.123 get automatic precision tracking (DECIMAL(4,3)). For floating point, use either the keyword prefix (FLOAT '1.1', DOUBLE '1.1') or scientific notation (1.1e0 → DOUBLE).

Other scalar literals

Strings, booleans, dates, timestamps, and JSON each have their own syntax:

SELECT
    TYPEOF('A') AS F_VARCHAR,
    TYPEOF(TRUE) AS F_BOOLEAN,
    TYPEOF(DATE '2024-10-15') AS F_DATE,
    TYPEOF(TIMESTAMP '2024-10-15 10:04:00') AS F_TIMESTAMP,
    TYPEOF(JSON '"A"') AS F_JSON,
;

Strings use single quotes only — 'A', never "A". Temporal literals require a keyword prefix: DATE '2024-10-15', TIMESTAMP '2024-10-15 10:04:00'. Timestamps support up to microsecond precision: TIMESTAMP '2024-10-15 10:04:00.123456'. JSON literals wrap JSON content in single quotes after the JSON keyword.

Complex type literals

Arrays and rows let you build structured data inline:

SELECT
    TYPEOF(ARRAY[1,2,3]) AS F_ARRAY,
    TYPEOF(ROW(1, 'A')) AS F_ROW,
    TYPEOF(ARRAY[ROW(1 as col1, 'A' as col2)]) AS F_ARRAY_OF_ROWS,
;

ARRAY[1,2,3] creates a homogeneous list. ROW(1, 'A') creates a struct with auto-generated field names. Add AS to name the fields: ROW(1 as col1, 'A' as col2). Nest them — ARRAY[ROW(...)] — to create the array-of-rows structure that is central to FeatureQL's data model.

Special values

FeatureQL has two kinds of "nothing" — NULL and EMPTY — and they behave differently:

SELECT
    EMPTY,
    TYPEOF(EMPTY),
    EMPTY(),
    TYPEOF(EMPTY()),
    NULL::VARCHAR,
    TYPEOF(NULL),
    NULL()::VARCHAR,
    TYPEOF(NULL()),
    NULL(DOUBLE)::VARCHAR,
    TYPEOF(NULL(DOUBLE)),
    -- EMPTY::BIGINT,  -- You cannot cast EMPTY to another type
    -- NULL::EMPTY  -- We cannot cast as EMPTY
    -- NULL::UNSPECIFIED  -- We cannot cast as UNSPECIFIED
;

NULL works like SQL's NULL: it represents a missing value and can be cast to any type. NULL without a type is UNSPECIFIED; NULL(DOUBLE) creates a typed null directly. NULL(DOUBLE) and NULL::DOUBLE are equivalent — both produce a typed null.

EMPTY is different — it represents an explicitly empty value used for optional function parameters. Unlike NULL, EMPTY cannot be cast to another type. If you try EMPTY::BIGINT, you get an error.