{"id":540,"date":"2018-12-24T11:37:00","date_gmt":"2018-12-24T11:37:00","guid":{"rendered":"http:\/\/happily70.dothome.co.kr\/?p=540"},"modified":"2019-02-07T15:26:30","modified_gmt":"2019-02-07T15:26:30","slug":"is-null-is-not-null","status":"publish","type":"post","link":"http:\/\/happily70.dothome.co.kr\/?p=540","title":{"rendered":"IS NULL, IS NOT NULL"},"content":{"rendered":"

NULL<\/strong>
\n– DB\uc5d0\uc11c NULL\uc774 \uc77c\ubc18\uc801\uc778 \uac12\uacfc\ub294 \ub2e4\ub974\uac8c \ucde8\uae09\ub41c\ub2e4.<\/strong>
\n– \uc544\uc9c1 \uc815\uc758\ub418\uc9c0 \uc54a\uc740 \uac12.
\n– 0(\uc22b\uc790) \ub610\ub294 \uacf5\ubc31(\ubb38\uc790)\uacfc \ub2e4\ub974\ub2e4.
\n– \ud14c\uc774\ube14\uc744 \uc0dd\uc131\ud560 \ub54c NOT NULL \ub610\ub294 PRIMARY KEY\ub85c \uc815\uc758\ub418\uc9c0 \uc54a\uc740 \ubaa8\ub4e0 \ub370\uc774\ud130 \uc720\ud615\uc740 \ub110 \uac12\uc744 \ud3ec\ud568\ud560 \uc218 \uc788\ub2e4.
\n– NULL \uac12\uc744 \ud3ec\ud568\ud558\ub294 \uc5f0\uc0b0\uc758 \uacbd\uc6b0 \uacb0\uacfc \uac12\ub3c4 NULL\uc774\ub2e4. \ubaa8\ub974\ub294 \ub370\uc774\ud130\uc5d0 \uc22b\uc790\ub97c \ub354\ud558\uac70\ub098 \ube7c\ub3c4 \uacb0\uacfc\ub294 \ub9c8\ucc2c\uac00\uc9c0\ub85c \ubaa8\ub974\ub294 \ub370\uc774\ud130\uc778 \uac83\uacfc \uac19\ub2e4.
\n– \uacb0\uacfc\uac12\uc744 NULL\uc774 \uc544\ub2cc \ub2e4\ub978 \uac12\uc744 \uc5bb\uace0\uc790 \ud560 \ub54c NVL\/ISNULL \ud568\uc218\ub97c \uc0ac\uc6a9\ud55c\ub2e4.
\n– NULL \uac12\uc758 \ub300\uc0c1\uc774 \uc22b\uc790 \uc720\ud615 \ub370\uc774\ud130\uc778 \uacbd\uc6b0\ub294 \uc8fc\ub85c 0(Zero)\uc73c\ub85c, \ubb38\uc790 \uc720\ud615 \ub370\uc774\ud130\uc778 \uacbd\uc6b0\uc5d0\ub294 \ube14\ub7ad\ud06c\ubcf4\ub2e4\ub294 ‘x’ \uac19\uc740 \ud574\ub2f9 \uc2dc\uc2a4\ud15c\uc5d0\uc11c \uc758\ubbf8\uc5c6\ub294 \ubb38\uc790\ub85c \ubc14\uafb8\ub294 \uacbd\uc6b0\uac00 \ub9ce\ub2e4.<\/p>\n

IS NULL<\/strong><\/p>\n

\r\n-- NULL\uc778 \ub370\uc774\ud130\r\nSELECT *\r\nFROM test\r\nWHERE score IS NULL;\r\n<\/pre>\n
IS NOT NULL<\/strong><\/p>\n
\r\n-- NULL\uc774 \uc544\ub2cc \ub370\uc774\ud130\r\nSELECT *\r\nFROM test\r\nWHERE score IS NOT NULL;\r\n<\/pre>\n
IFNULL<\/strong><\/p>\n
\r\n-- NULL\uc774\uba74 0\uc73c\ub85c \uce58\ud658.\r\nSELECT IFNULL(score, 0) FROM test;\r\n<\/pre>\n
COALESCE<\/strong><\/p>\n
\r\n-- NULL\uc774\uba74 0\uc73c\ub85c \uce58\ud658.\r\nSELECT COALESCE(score, 0) FROM test;\r\n<\/pre>\n
\r\nIFNULL\uacfc COALESCE \ucc28\uc774.<\/strong>\r\nCOALESCE() is in all the major databases, while IFNULL() isn't in SQL Server which uses ISNULL()instead. Performance should be no different. \u2013  Hart CO Nov 12 '14 at 18:56\r\n\uacb0\uacfc\ub294 \uac19\uc9c0\ub9cc. COALESCE\uac00 \ubaa8\ub4e0 \ub370\uc774\ud130\ubca0\uc774\uc2a4\uc5d0\uc11c \uc0ac\uc6a9\uac00\ub2a5\ud558\ub2c8 COALESCE\ub97c \uad8c\uc7a5\ud55c\ub2e4. \r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
NULL – DB\uc5d0\uc11c NULL\uc774 \uc77c\ubc18\uc801\uc778 \uac12\uacfc\ub294 \ub2e4\ub974\uac8c \ucde8\uae09\ub41c\ub2e4. – \uc544\uc9c1 \uc815\uc758\ub418\uc9c0 \uc54a\uc740 \uac12. – 0(\uc22b\uc790) \ub610\ub294 \uacf5\ubc31(\ubb38\uc790)\uacfc \ub2e4\ub974\ub2e4. – \ud14c\uc774\ube14\uc744 \uc0dd\uc131\ud560 \ub54c NOT NULL \ub610\ub294 PRIMARY KEY\ub85c \uc815\uc758\ub418\uc9c0 \uc54a\uc740 \ubaa8\ub4e0 \ub370\uc774\ud130 \uc720\ud615\uc740 \ub110 \uac12\uc744 \ud3ec\ud568\ud560 \uc218 \uc788\ub2e4. – NULL \uac12\uc744 \ud3ec\ud568\ud558\ub294 \uc5f0\uc0b0\uc758 \uacbd\uc6b0 \uacb0\uacfc \uac12\ub3c4 NULL\uc774\ub2e4. \ubaa8\ub974\ub294 \ub370\uc774\ud130\uc5d0 \uc22b\uc790\ub97c \ub354\ud558\uac70\ub098 \ube7c\ub3c4 \uacb0\uacfc\ub294 \ub9c8\ucc2c\uac00\uc9c0\ub85c \ubaa8\ub974\ub294 \ub370\uc774\ud130\uc778<\/p>\n