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COUNT(CASE WHEN HIREDATE = '80' THEN HIREDATE ELSE NULL END )AS "1980" ,COUNT(CASE WHEN HIREDATE = '81' THEN HIREDATE ELSE NULL END) AS "1981" ,COUNT(CASE WHEN HIREDATE = '82' THEN HIREDATE ELSE NULL END) AS "1982" ,COUNT(CASE WHEN HIREDATE = '83' THEN HIREDATE ELSE NULL END) AS "1983" ,COUNT(*) AS TOT FROM EMP COUNT()¿¡ CASE¹®À» »ç¿ëÇؼ °ªÀ» ³ÖÀ» ¼ö ÀÖ½À´Ï´Ù. COUNT´Â NULL°ªÀ» ¼¼Áö ¾Ê½À´Ï´Ù. CASE WHEN HIREDATE = '83' THEN HIREDATE ELSE NULL END ÀÌ·¸°Ô CASE¿Í COUNT¸¦ Á¶ÇÕÇÏ½Ã¸é ¿øÇÏ´Â °ªÀ» COUNTÇÒ ¼ö ÀÖ½À´Ï´Ù. |
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SELECT substr(hiredate, 1, 2), COUNT(*) FROM EMP GROUP BY substr(hiredate, 1, 2)
¶ó°í ÀÛ¼ºÇϽøé substr(hiredate, 1, 2) ±×·ìÀ¸·Î ³ª´µ¾î¼ Ä«¿îÆ®¸¦ ÇÕ´Ï´Ù.
2. FROM DAUL Àº °¡»óÅ×À̺íÀÌ´Ï ´ç¿¬È÷ 1ÁÙ¸¸ ÀÛ¼ºÇßÀ¸´Ï 1ÁÙ¸¸ ³ª¿É´Ï´Ù.
FROM EMP´Â ½ÇÅ×ÀÌºí¿¡ 16 ROW°¡ ÀÖÀ¸´Ï ´ç¿¬È÷ 16ÁÙÀÌ ³ª¿É´Ï´Ù.
EMP Å×ÀÌºí¿¡¼ 1ÁÙ¸¸ Ãâ·ÂÇÒ·Á¸é Áý°èÇÔ¼ö(SUM, COUNT µî) ȤÀº LIMIT, ROWNUMÀ» ÀÌ¿ëÇؼ ÇÑÁÙ¸¸ Ãâ·ÂÇÒ ¼öµµ ÀÖ½À´Ï´Ù.