■예 4_1_9  ||  UNION의 칼럼유형
____SELECT '20090101' AS SABUN, '이호상' AS NAME FROM DUAL
UNION
SELECT '20090102' AS SABUN, '홍길동' AS NAME FROM DUAL;

■예 4_1_10  ||  UNION의 칼럼개수
SELECT '20090101' AS SABUN, '이호상' AS NAME, 'LEE HO SANG' AS ENG_NAME FROM DUAL
UNION
SELECT '20090102' AS SABUN, '홍길동' AS NAME FROM DUAL;

■예 4_1_11  ||  UNION의 사용
SELECT '20090101' AS SABUN, '이호상' AS NAME FROM DUAL
UNION
SELECT '20090102' AS SABUN, '홍길동' AS NAME FROM DUAL;

■예 4_1_12  ||  UNION의 특성
SELECT '20090101' AS SABUN, '이호상' AS NAME FROM DUAL
UNION
SELECT '20090102' AS SABUN, '홍길동' AS NAME FROM DUAL
UNION
SELECT '20090102' AS SABUN, '김길동' AS NAME FROM DUAL
UNION
SELECT '20090102' AS SABUN, '홍길동' AS NAME FROM DUAL
UNION
SELECT '20090102' AS SABUN, '홍길동' AS NAME FROM DUAL;

■예 4_1_13  ||  UNION ALL의 특성
SELECT '20090101' AS SABUN, '이호상' AS NAME FROM DUAL
UNION ALL
SELECT '20090102' AS SABUN, '홍길동' AS NAME FROM DUAL
UNION ALL
SELECT '20090102' AS SABUN, '김길동' AS NAME FROM DUAL
UNION ALL
SELECT '20090102' AS SABUN, '홍길동' AS NAME FROM DUAL
UNION ALL
SELECT '20090102' AS SABUN, '홍길동' AS NAME FROM DUAL;

■예 4_1_14  ||  GROUP BY 의 사용
SELECT JOIN_GBN_CODE, COUNT(SABUN), MAX(NAME), MIN(ENG_NAME),
COUNT(ENG_NAME), ROUND(AVG(SALARY))
FROM INSA
GROUP BY JOIN_GBN_CODE;

■예 4_1_15  ||  GROUP BY 와 HAVING절 사용
SELECT JOIN_GBN_CODE, COUNT(SABUN), MAX(NAME), MIN(ENG_NAME),
       COUNT(ENG_NAME), ROUND(AVG(SALARY))
FROM INSA
GROUP BY JOIN_GBN_CODE
HAVING  ROUND(AVG(SALARY)) < 2700;

■예 4_1_16  ||  예제 풀이 SQL
SELECT NO, JOIN_GBN_CODE, COUNT(SABUN), MAX(NAME), MIN(ENG_NAME),
       COUNT(ENG_NAME), ROUND(AVG(SALARY))
FROM INSA,
     (SELECT 1 AS NO FROM DUAL
     UNION
     SELECT 2 AS NO FROM DUAL)
GROUP BY NO, JOIN_GBN_CODE;

■예 4_1_17  ||  GROUP BY와 ORDER BY
SELECT DECODE(NO,1,JOIN_GBN_CODE,'합계'), COUNT(SABUN), MAX(NAME), MIN(ENG_NAME),
       COUNT(ENG_NAME), ROUND(AVG(SALARY))
FROM INSA,
     (SELECT 1 AS NO FROM DUAL
     UNION
     SELECT 2 AS NO FROM DUAL)
GROUP BY DECODE(NO,1,JOIN_GBN_CODE,'합계')
ORDER BY DECODE(NO,1,JOIN_GBN_CODE,'합계');

■예 4_1_18  ||  GROUP BY와 SORTING
SELECT DECODE(NO,1,JOIN_GBN_CODE,'합계'), COUNT(SABUN), MAX(NAME), MIN(ENG_NAME),
       COUNT(ENG_NAME), ROUND(AVG(SALARY))
FROM INSA,
     (SELECT 1 AS NO FROM DUAL
     UNION
     SELECT 2 AS NO FROM____ DUAL)
GROUP BY DECODE(NO,1,JOIN_GBN_CODE,'합계');