여러 SQL문을 합쳐서 하나의 SQL문으로 표현하기 위한 SQL 문법입니다.
SELECT column1, column2,...
FROM tablename1
UNION
SELECT column1-1, column2-1,...
FROM tablename2
SELECT column1, column2,...
FROM tablename1
UNION ALL
SELECT column1-1, column2-1,...
FROM tablename2
가정)
SELECT ID, NAME
FROM testTABLE
UNION
SELECT NUMBER, NAME
FROM exampleTABLE
SELECT ID, NAME
FROM testTABLE
UNION ALL
SELECT NUMBER, NAME
FROM exampleTABLE