SQLでテーブル結合処理を行えるものの一つとして、UNIONがある。UNIONは、テーブルを縦方向に結合する。他の結合処理が可能なものとして、OUTER JOINとINNER JOINがあるが、これらは横方向にテーブルを結合する。 以下では、UNIONについての説明を行う。さらに ...

A SQL union is a set operation that allows you to combine the results of two or more queries into a single result set. The queries must have the same number and type of columns, but they can come from ...

If you work with data from different sources, you might need to combine them into a single table for analysis or reporting. One way to do that is by using UNION in SQL, a function that allows you to ...

expression Any valid query expression that returns a collection to combine with the collection All expressions must be of the same type or of a common base or derived type as expression. UNION ...

In this chapter, we explore a new way of joining data: set operations. Along the way, we'll highlight key differences between set operations and the joins we have seen so far. In this lesson, we will ...