====== UNION query======
===== Usage =====

This type of query is similar to the [[https://en.wikipedia.org/wiki/Set_operations_(SQL)#UNION_operator|SQL UNION]] function.
These queries are used to display the rows extractedby two (or more) subqueries.
===== Difference from query =====

==== Selecting Subqueries ====

As for the [[:en:v8_0_0:designer:menus:accueil:nouvellerequete:rapprochement|matching], at [[:en:v8_0_0:designer:menus:accueil:nouvellerequete:choixtables|data source selection]], no table can be selected, only queries.

{{:v8_0_0:designer:menus:accueil:nouvellerequete:pasted:20200625-144813.png?nolink&500}}

<WRAP round important>
All subqueries must use the same data source as the one selected in the union query.
</WRAP>

<WRAP round alert>
Vigilens checks that the structures of the subqueries are consistent with each other, i.e. :
  * they have the same number of fields
  * the field types (in the order they appear) are identical
</WRAP>

==== Screens out ====

The following screens of the [[:en:v8_0_0:designer:menus:accueil:nouvellerequete:consultation|inquiry]] are absent when creating a UNION :
  * [[:en:v8_0_0:designer:menus:accueil:nouvellerequete:jointures|Join screen]]
  * [[:en:v8_0_0:designer:menus:accueil:nouvellerequete:criteres|Criteria screen]]
  * [[:en:v8_0_0:designer:menus:accueil:nouvellerequete:consultation#annexes|Appendices screen.]]
  * [[:en:v8_0_0:designer:menus:accueil:nouvellerequete:consultation#decimales_devises|Currency decimal screen]]