# Union

The `|` operator was available in XPath 1.0; the keyword `union` has been added in XPath 2.0 as a synonym, because it is familiar to SQL users.

The expression `E1 union E2` selects all nodes that are in either `E1` or `E2` or both. Both expressions must return sequences of nodes. The results are returned in document order. For example, `/book/(chapter | appendix)/sections` returns all `section` elements within a `chapter` or `appendix` of the selected `book` element.

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