Name	Description
union.tag	Dot notation serves as an alias for union_extract.
union_extract(union, 'tag')	Extract the value with the named tags from the union. NULL if the tag is not currently selected.
union_value(tag := any)	Create a single member UNION containing the argument value. The tag of the value will be the bound variable name.
union_tag(union)	Retrieve the currently selected tag of the union as an Enum.

union.tag

Description	Dot notation serves as an alias for union_extract.
Example	(union_value(k := 'hello')).k
Result	string

union_extract(union, 'tag')

Description	Extract the value with the named tags from the union. NULL if the tag is not currently selected.
Example	union_extract(s, 'k')
Result	hello

union_value(tag := any)

Description	Create a single member UNION containing the argument value. The tag of the value will be the bound variable name.
Example	union_value(k := 'hello')
Result	'hello'::UNION(k VARCHAR)

union_tag(union)

Description	Retrieve the currently selected tag of the union as an Enum.
Example	union_tag(union_value(k := 'foo'))
Result	'k'