libpqxx
7.9.0
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Traits describing a type's "null value," if any. More...
#include <strconv.hxx>
Static Public Member Functions | |
static bool | is_null (TYPE const &value) |
Is value a null? More... | |
static TYPE | null () |
Return a null value. More... | |
Static Public Attributes | |
static bool | has_null |
Does this type have a null value? More... | |
static bool | always_null |
Is this type always null? More... | |
Traits describing a type's "null value," if any.
Some C++ types have a special value or state which correspond directly to SQL's NULL.
The nullness
traits describe whether it exists, and whether a particular value is null.
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Is value
a null?
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Return a null value.
Don't use this in generic code to compare a value and see whether it is null. Some types may have multiple null values which do not compare as equal, or may define a null value which is not equal to anything including itself, like in SQL.
Referenced by pqxx::field::as(), and pqxx::from_string().
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Is this type always null?
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Does this type have a null value?