libpqxx
The C++ client library for PostgreSQL
pqxx::nullness< TYPE, ENABLE > Struct Template Reference

Traits describing a type's "null value," if any. More...

Static Public Member Functions

static bool is_null (TYPE const &value)
 Is value a null?
 
static TYPE null ()
 Return a null value. More...
 

Static Public Attributes

static bool has_null
 Does this type have a null value?
 
static bool always_null
 Is this type always null?
 

Detailed Description

template<typename TYPE, typename ENABLE = void>
struct pqxx::nullness< TYPE, ENABLE >

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.

Member Function Documentation

◆ null()

template<typename TYPE , typename ENABLE = void>
static TYPE pqxx::nullness< TYPE, ENABLE >::null ( )
static

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.


The documentation for this struct was generated from the following file: