如何在PostgreSQL中钳制浮点

我找到的解决方案是:

SELECT ACOS(GREATEST(-1, LEAST(1, 1 + 0.0000000001));

-- example: clamp(subject, min, max)
CREATE FUNCTION clamp(integer, integer, integer) RETURNS integer
    AS 'select GREATEST($2, LEAST($3, $1));'
    LANGUAGE SQL
    IMMUTABLE
    RETURNS NULL ON NULL INPUT;

-- example: clamp_above(subject, max)
CREATE FUNCTION clamp_above(integer, integer) RETURNS integer
    AS 'select LEAST($1, $2);'
    LANGUAGE SQL
    IMMUTABLE
    RETURNS NULL ON NULL INPUT;

-- example: clamp_below(subject, min)
CREATE FUNCTION clamp_below(integer, integer) RETURNS integer
    AS 'select GREATEST($1, $2);'
    LANGUAGE SQL
    IMMUTABLE
    RETURNS NULL ON NULL INPUT;