#include namespace DB { REGISTER_FUNCTION(IsNotDistinctFrom) { factory.registerFunction( FunctionDocumentation{ .description = R"( Performs a null-safe comparison between two values. This function will consider two `NULL` values as identical and will return `true`, which is distinct from the usual equals behavior where comparing two `NULL` values would return `NULL`. Currently, this function can only be used in the `JOIN ON` section of a query. [example:join_on_is_not_distinct_from] )", .examples{ {"join_on_is_not_distinct_from", "SELECT * FROM (SELECT NULL AS a) AS t1 JOIN (SELECT NULL AS b) AS t2 ON isNotDistinctFrom(t1.a, t2.b)", "NULL\tNULL"}, }, .categories = {"Comparison", "Join Operators"}, }); } }