[Oracle] INNER-JOIN 결과 ROW 수

1번 테이블

SELECT 'A' T1_COL1 FROM DUAL UNION ALL
SELECT 'B' T1_COL1 FROM DUAL UNION ALL
SELECT 'B' T1_COL1 FROM DUAL UNION ALL
SELECT 'C' T1_COL1 FROM DUAL

 

2번 테이블

SELECT 'A' T2_COL1 FROM DUAL UNION ALL
SELECT 'B' T2_COL1 FROM DUAL UNION ALL
SELECT 'B' T2_COL1 FROM DUAL UNION ALL
SELECT 'B' T2_COL1 FROM DUAL UNION ALL
SELECT 'D' T2_COL1 FROM DUAL

 

 

1번 테이블과 2번테이블 INNER-JOIN

SELECT T1.T1_COL1, T2.T2_COL1
FROM ( SELECT 'A' T1_COL1 FROM DUAL UNION ALL
       SELECT 'B' T1_COL1 FROM DUAL UNION ALL
       SELECT 'B' T1_COL1 FROM DUAL UNION ALL
       SELECT 'C' T1_COL1 FROM DUAL ) T1,
     ( SELECT 'A' T2_COL1 FROM DUAL UNION ALL
       SELECT 'B' T2_COL1 FROM DUAL UNION ALL
       SELECT 'B' T2_COL1 FROM DUAL UNION ALL
       SELECT 'B' T2_COL1 FROM DUAL UNION ALL
       SELECT 'D' T2_COL1 FROM DUAL ) T2
WHERE T1.T1_COL1 = T2.T2_COL1

 

INNER-JOIN 결과

 

'A' : 1 * 1 = 1 ROW 'B' : 2 * 3 = 6 ROW 최종 결과 ROW 수 7 ROW

 

 

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