{"id":476178,"date":"2023-08-09T07:26:52","date_gmt":"2023-08-09T07:26:52","guid":{"rendered":""},"modified":"2023-09-05T11:12:10","modified_gmt":"2023-09-05T11:12:10","slug":"cardinality-sql","status":"publish","type":"wiki","link":"https:\/\/oneproxy.pro\/kr\/wiki\/cardinality-sql\/","title":{"rendered":"\uce74\ub514\ub110\ub9ac\ud2f0(SQL)"},"content":{"rendered":"<p>SQL\uc758 \uce74\ub514\ub110\ub9ac\ud2f0\ub294 \ub370\uc774\ud130\ubca0\uc774\uc2a4 \ud14c\uc774\ube14\uc758 \uc5f4 \ub610\ub294 \uc778\ub371\uc2a4\uc5d0 \uc788\ub294 \uace0\uc720\ud55c \uac12 \uc218\ub97c \ub098\ud0c0\ub0c5\ub2c8\ub2e4. \uc774\ub294 \ub370\uc774\ud130 \ubc30\ud3ec\uc5d0 \ub300\ud55c \ud1b5\ucc30\ub825\uc744 \uc81c\uacf5\ud558\uace0 \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc5d4\uc9c4\uc774 \uc2e4\ud589 \uacc4\ud68d\uc744 \uc0dd\uc131\ud560 \ub54c \uc815\ubcf4\uc5d0 \uc785\uac01\ud55c \uacb0\uc815\uc744 \ub0b4\ub9ac\ub294 \ub370 \ub3c4\uc6c0\uc774 \ub418\ubbc0\ub85c \ucffc\ub9ac \ucd5c\uc801\ud654 \ubc0f \uc131\ub2a5 \ud29c\ub2dd\uc5d0\uc11c \uc911\uc694\ud55c \uc5ed\ud560\uc744 \ud569\ub2c8\ub2e4. \uce74\ub514\ub110\ub9ac\ud2f0\ub294 \ub370\uc774\ud130\ubca0\uc774\uc2a4 \ubd84\uc57c\uc758 \uae30\ubcf8 \uac1c\ub150\uc73c\ub85c \ub2e4\uc591\ud55c \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uad00\ub9ac \uc2dc\uc2a4\ud15c(DBMS)\uc5d0\uc11c \ub110\ub9ac \uc0ac\uc6a9\ub429\ub2c8\ub2e4.<\/p>\n<h2>\uce74\ub514\ub110\ub9ac\ud2f0(SQL)\uc758 \uc720\ub798\uc640 \ucd5c\ucd08 \uc5b8\uae09\uc758 \uc5ed\uc0ac<\/h2>\n<p>SQL\uc758 \uce74\ub514\ub110\ub9ac\ud2f0 \uac1c\ub150\uc740 \uad00\uacc4\ud615 \ub370\uc774\ud130\ubca0\uc774\uc2a4\uc758 \ucd08\uae30 \uc2dc\ub300\ub85c \uac70\uc2ac\ub7ec \uc62c\ub77c\uac11\ub2c8\ub2e4. \uad00\uacc4\ud615 \ubaa8\ub378\uc740 EF Codd \ubc15\uc0ac\uac00 1970\ub144\uc5d0 \ucd9c\ud310\ud55c \ud68d\uae30\uc801\uc778 \ub17c\ubb38 &quot;\ub300\uaddc\ubaa8 \uacf5\uc720 \ub370\uc774\ud130 \uc740\ud589\uc744 \uc704\ud55c \ub370\uc774\ud130\uc758 \uad00\uacc4\ud615 \ubaa8\ub378&quot;\uc5d0\uc11c \uc18c\uac1c\ub418\uc5c8\uc2b5\ub2c8\ub2e4. \uc774 \ub17c\ubb38\uc5d0\uc11c Codd\ub294 \ub370\uc774\ud130\ub97c \ud589\uacfc \uc5f4\uc774 \uc788\ub294 \ud14c\uc774\ube14\ub85c \ud45c\ud604\ud558\ub294 \uc544\uc774\ub514\uc5b4\ub97c \uc81c\uc2dc\ud588\uc2b5\ub2c8\ub2e4. \ub370\uc774\ud130\ub97c \uc870\uc791\ud558\uae30 \uc704\ud55c \uc77c\ub828\uc758 \uc218\ud559\uc801 \uc5f0\uc0b0\uc785\ub2c8\ub2e4.<\/p>\n<p>&quot;\uce74\ub514\ub110\ub9ac\ud2f0&quot;\ub77c\ub294 \uc6a9\uc5b4\ub294 \ub098\uc911\uc5d0 \uad00\uacc4\ud615 \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uad00\ub9ac \uc2dc\uc2a4\ud15c\uc774 \ubc1c\uc804\ud558\uace0 \uc131\uc219\ud574\uc9c0\uba74\uc11c \ub300\uc911\ud654\ub418\uc5c8\uc2b5\ub2c8\ub2e4. \uc774\ub294 \uac00\uc7a5 \ud6a8\uc728\uc801\uc778 \uc2e4\ud589 \uacc4\ud68d\uc744 \uc120\ud0dd\ud558\uae30 \uc704\ud574 \ucffc\ub9ac\uc5d0\uc11c \ubc18\ud658\ub420 \ud589 \uc218\ub97c \ucd94\uc815\ud558\ub294 \uac83\uc774 \ud544\uc218\uc801\uc778 \ucffc\ub9ac \ucd5c\uc801\ud654\uc758 \uc911\uc694\uc131\uc73c\ub85c \uc778\ud574 \ub450\uac01\uc744 \ub098\ud0c0\ub0c8\uc2b5\ub2c8\ub2e4.<\/p>\n<h2>\uce74\ub514\ub110\ub9ac\ud2f0(SQL)\uc5d0 \ub300\ud55c \uc790\uc138\ud55c \uc815\ubcf4<\/h2>\n<p>SQL \ub370\uc774\ud130\ubca0\uc774\uc2a4\uc758 \ub9e5\ub77d\uc5d0\uc11c \uce74\ub514\ub110\ub9ac\ud2f0\ub294 \uc5f4\uc774\ub098 \uc778\ub371\uc2a4\uc5d0 \uc788\ub294 \uace0\uc720 \uac12\uc758 \uc218\ub97c \ub098\ud0c0\ub0c5\ub2c8\ub2e4. \uc774\ub294 \ud14c\uc774\ube14\uc758 \ub370\uc774\ud130 \ubd84\ud3ec\uc5d0 \ub300\ud55c \ud1b5\uacc4 \uc815\ubcf4\ub97c \uc81c\uacf5\ud558\uc5ec \ucffc\ub9ac \ucd5c\uc801\ud654 \ud504\ub85c\uadf8\ub7a8\uc774 \ucffc\ub9ac\ub97c \ucc98\ub9ac\ud558\ub294 \uac00\uc7a5 \ud6a8\uc728\uc801\uc778 \ubc29\ubc95\uc744 \uacb0\uc815\ud558\ub294 \ub370 \ub3c4\uc6c0\uc774 \ub429\ub2c8\ub2e4.<\/p>\n<h2>\uce74\ub514\ub110\ub9ac\ud2f0(SQL)\uc758 \ub0b4\ubd80 \uad6c\uc870\uc640 \uc791\ub3d9 \ubc29\uc2dd<\/h2>\n<p>Cardinality\uc758 \ub0b4\ubd80 \uad6c\uc870\ub294 \ub370\uc774\ud130\ubca0\uc774\uc2a4 \ud1b5\uacc4 \ub0b4\uc5d0\uc11c \uc720\uc9c0\ub429\ub2c8\ub2e4. DBMS\ub294 \ud589 \uc218, \uace0\uc720 \uac12 \ubc0f \ub370\uc774\ud130 \ubd84\ud3ec\uc5d0 \ub300\ud55c \uc815\ubcf4\ub97c \ud3ec\ud568\ud558\ub294 \ud14c\uc774\ube14 \ubc0f \uc778\ub371\uc2a4\uc5d0 \ub300\ud55c \ud1b5\uacc4\ub97c \uc800\uc7a5\ud569\ub2c8\ub2e4. \ucffc\ub9ac\uac00 \uc2e4\ud589\ub418\uba74 \ucffc\ub9ac \ucd5c\uc801\ud654 \ud504\ub85c\uadf8\ub7a8\uc740 \uc774\ub7ec\ud55c \ud1b5\uacc4\ub97c \uc0ac\uc6a9\ud558\uc5ec \uce74\ub514\ub110\ub9ac\ud2f0\ub97c \ucd94\uc815\ud558\uace0 \ucd5c\uc801\uc758 \ucffc\ub9ac \uc2e4\ud589 \uacc4\ud68d\uc744 \uc120\ud0dd\ud569\ub2c8\ub2e4.<\/p>\n<p>\ub370\uc774\ud130\ubca0\uc774\uc2a4 \uad00\ub9ac \uc2dc\uc2a4\ud15c\uc740 \uce74\ub514\ub110\ub9ac\ud2f0\ub97c \ud6a8\uc728\uc801\uc73c\ub85c \ucd94\uc801\ud558\uae30 \uc704\ud574 \ub2e4\uc591\ud55c \uc54c\uace0\ub9ac\uc998\uacfc \ub370\uc774\ud130 \uad6c\uc870\ub97c \uc0ac\uc6a9\ud560 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \uc774\ub7ec\ud55c \uad6c\uc870\ub294 \ub370\uc774\ud130\ubca0\uc774\uc2a4\uc5d0\uc11c \ub370\uc774\ud130 \ubcc0\uacbd\uc774 \ubc1c\uc0dd\ud560 \ub54c \uc815\uae30\uc801\uc73c\ub85c \ub610\ub294 \uc694\uccad \uc2dc \uc5c5\ub370\uc774\ud2b8\ub429\ub2c8\ub2e4.<\/p>\n<h2>Cardinality(SQL)\uc758 \uc8fc\uc694 \uae30\ub2a5 \ubd84\uc11d<\/h2>\n<p>SQL\uc758 \uce74\ub514\ub110\ub9ac\ud2f0\uc758 \uc8fc\uc694 \uae30\ub2a5\uc740 \ub2e4\uc74c\uacfc \uac19\uc2b5\ub2c8\ub2e4.<\/p>\n<ol>\n<li>\n<p><strong>\ucffc\ub9ac \ucd5c\uc801\ud654:<\/strong> \uce74\ub514\ub110\ub9ac\ud2f0\ub294 \ucffc\ub9ac \uc2e4\ud589 \uacc4\ud68d\uc744 \uacb0\uc815\ud558\ub294 \ub370 \uc911\uc694\ud55c \uc694\uc18c\uc785\ub2c8\ub2e4. \uce74\ub514\ub110\ub9ac\ud2f0\uac00 \ub192\uc744\uc218\ub85d \uc778\ub371\uc2a4\uac00 \ub354 \uc120\ud0dd\uc801\uc73c\ub85c \uc120\ud0dd\ub418\uc5b4 \ucffc\ub9ac \uc2e4\ud589 \uc18d\ub3c4\uac00 \ube68\ub77c\uc9c0\ub294 \uacbd\uc6b0\uac00 \ub9ce\uc2b5\ub2c8\ub2e4.<\/p>\n<\/li>\n<li>\n<p><strong>\ub370\uc774\ud130 \ubd84\ud3ec \ubd84\uc11d:<\/strong> \uce74\ub514\ub110\ub9ac\ud2f0\ub294 \uc5f4\uc758 \ub370\uc774\ud130 \uac12 \ubd84\ud3ec\uc5d0 \ub300\ud55c \ud1b5\ucc30\ub825\uc744 \uc81c\uacf5\ud569\ub2c8\ub2e4. \uc774\ub294 \uc65c\uace1\ub41c \ub370\uc774\ud130\ub098 \uc911\ubcf5 \ud56d\ubaa9\uacfc \uac19\uc740 \uc7a0\uc7ac\uc801\uc778 \ub370\uc774\ud130 \ud488\uc9c8 \ubb38\uc81c\ub97c \uc2dd\ubcc4\ud558\ub294 \ub370 \ub3c4\uc6c0\uc774 \ub429\ub2c8\ub2e4.<\/p>\n<\/li>\n<li>\n<p><strong>\uc870\uc778 \ucd5c\uc801\ud654:<\/strong> \uce74\ub514\ub110\ub9ac\ud2f0\ub294 \uc870\uc778 \uc791\uc5c5\uc744 \ucd5c\uc801\ud654\ud558\ub294 \ub370 \uc911\uc694\ud55c \uc5ed\ud560\uc744 \ud569\ub2c8\ub2e4. \ub370\uc774\ud130\ubca0\uc774\uc2a4 \ucd5c\uc801\ud654 \ud504\ub85c\uadf8\ub7a8\uc740 \uc870\uc778\ub41c \uc5f4\uc758 \uce74\ub514\ub110\ub9ac\ud2f0\ub97c \uc0ac\uc6a9\ud558\uc5ec \uc911\ucca9 \ub8e8\ud504 \uc870\uc778, \ud574\uc2dc \uc870\uc778 \ub610\ub294 \ubcd1\ud569 \uc870\uc778\uacfc \uac19\uc740 \uac00\uc7a5 \ud6a8\uc728\uc801\uc778 \uc870\uc778 \uc804\ub7b5\uc744 \uc120\ud0dd\ud569\ub2c8\ub2e4.<\/p>\n<\/li>\n<li>\n<p><strong>\uc778\ub371\uc2a4 \ub514\uc790\uc778:<\/strong> \uce74\ub514\ub110\ub9ac\ud2f0\ub294 \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc778\ub371\uc2a4\uc758 \ud6a8\uc728\uc131\uc5d0 \uc601\ud5a5\uc744 \ubbf8\uce69\ub2c8\ub2e4. \ub0ae\uc740 \uce74\ub514\ub110\ub9ac\ud2f0 \uc5f4\uc740 \uc120\ud0dd\uc131\uc744 \ub9ce\uc774 \uc81c\uacf5\ud558\uc9c0 \uc54a\uae30 \ub54c\ubb38\uc5d0 \uc778\ub371\uc2f1\uc5d0 \uc801\ud569\ud558\uc9c0 \uc54a\uc740 \ubc18\uba74, \ub192\uc740 \uce74\ub514\ub110\ub9ac\ud2f0 \uc5f4\uc740 \uc778\ub371\uc2f1\uc5d0 \ub354 \ub098\uc740 \ud6c4\ubcf4\uc785\ub2c8\ub2e4.<\/p>\n<\/li>\n<\/ol>\n<h2>\uce74\ub514\ub110\ub9ac\ud2f0 \uc720\ud615(SQL)<\/h2>\n<p>\uce74\ub514\ub110\ub9ac\ud2f0\uc5d0\ub294 \uc138 \uac00\uc9c0 \uae30\ubcf8 \uc720\ud615\uc774 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n<ol>\n<li>\n<p><strong>\ub0ae\uc740 \uce74\ub514\ub110\ub9ac\ud2f0:<\/strong> \uce74\ub514\ub110\ub9ac\ud2f0\uac00 \ub0ae\uc740 \uc5f4\uc5d0\ub294 \ud14c\uc774\ube14\uc758 \ucd1d \ud589 \uc218\uc5d0 \ube44\ud574 \uc801\uc740 \uc218\uc758 \uace0\uc720 \uac12\uc774 \uc788\uc2b5\ub2c8\ub2e4. \uc77c\ubc18\uc801\uc778 \uc608\ub85c\ub294 \uc131\ubcc4 \ub610\ub294 \uad6d\uac00 \uc5f4\uc774 \uc788\uc73c\uba70, \uc77c\ubc18\uc801\uc73c\ub85c \uc5ec\ub7ec \ud589\uc5d0 \uac78\uccd0 \uba87 \uac1c\uc758 \uace0\uc720\ud55c \uac12\ub9cc \ubc18\ubcf5\ub429\ub2c8\ub2e4.<\/p>\n<\/li>\n<li>\n<p><strong>\ub192\uc740 \uce74\ub514\ub110\ub9ac\ud2f0:<\/strong> \uce74\ub514\ub110\ub9ac\ud2f0\uac00 \ub192\uc740 \uc5f4\uc5d0\ub294 \ud14c\uc774\ube14\uc758 \ucd1d \ud589 \uc218\uc5d0 \ube44\ud574 \uace0\uc720 \uac12 \uc218\uac00 \ub9ce\uc2b5\ub2c8\ub2e4. \uc608\ub97c \ub4e4\uc5b4 \uae30\ubcf8 \ud0a4\ub098 \uace0\uc720 \uc2dd\ubcc4\uc790 \uc5f4\uc740 \uac01 \ud589\uc5d0 \uace0\uc720\ud55c \uac12\uc774 \uc788\uc73c\ubbc0\ub85c \uce74\ub514\ub110\ub9ac\ud2f0\uac00 \ub192\uc740 \uacbd\ud5a5\uc774 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n<\/li>\n<li>\n<p><strong>\uc911\uac04 \uce74\ub514\ub110\ub9ac\ud2f0:<\/strong> \uc911\uac04 \uce74\ub514\ub110\ub9ac\ud2f0\ub294 \ub0ae\uc740 \uce74\ub514\ub110\ub9ac\ud2f0\uc640 \ub192\uc740 \uce74\ub514\ub110\ub9ac\ud2f0 \uc0ac\uc774\uc5d0 \uc18d\ud569\ub2c8\ub2e4. \uc911\uac04 \uce74\ub514\ub110\ub9ac\ud2f0\ub97c \uac16\ub294 \uc5f4\uc5d0\ub294 \uc801\ub2f9\ud55c \uc218\uc758 \uace0\uc720 \uac12\uc774 \uc788\uc73c\ubbc0\ub85c \ub0ae\uc740 \uce74\ub514\ub110\ub9ac\ud2f0 \uc5f4\ubcf4\ub2e4 \uc120\ud0dd\uc131\uc774 \ub192\uc9c0\ub9cc \ub192\uc740 \uce74\ub514\ub110\ub9ac\ud2f0 \uc5f4\ubcf4\ub2e4\ub294 \uc120\ud0dd\uc131\uc774 \ub5a8\uc5b4\uc9d1\ub2c8\ub2e4.<\/p>\n<\/li>\n<\/ol>\n<p>\ub2e4\uc74c\uc740 \uce74\ub514\ub110\ub9ac\ud2f0\uc758 \uc138 \uac00\uc9c0 \uc720\ud615\uc744 \ube44\uad50\ud55c \uac83\uc785\ub2c8\ub2e4.<\/p>\n<table>\n<thead>\n<tr>\n<th>\uce74\ub514\ub110\ub9ac\ud2f0 \uc720\ud615<\/th>\n<th>\uace0\uc720 \uac12\uc758 \uc218<\/th>\n<th>\uc120\ud0dd\uc131<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\ub0ae\uc740<\/td>\n<td>\uc57d\uac04\uc758<\/td>\n<td>\ub0ae\uc740<\/td>\n<\/tr>\n<tr>\n<td>\uc911\uac04<\/td>\n<td>\ubcf4\ud1b5\uc758<\/td>\n<td>\uc911\uac04<\/td>\n<\/tr>\n<tr>\n<td>\ub192\uc740<\/td>\n<td>\ub9ce\uc740<\/td>\n<td>\ub192\uc740<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h2>Cardinality(SQL)\uc758 \uc0ac\uc6a9\ubc29\ubc95\uacfc \uc0ac\uc6a9\uc5d0 \ub530\ub978 \ubb38\uc81c\uc810 \ubc0f \ud574\uacb0\ubc29\uc548<\/h2>\n<h3>SQL\uc5d0\uc11c \uce74\ub514\ub110\ub9ac\ud2f0\ub97c \uc0ac\uc6a9\ud558\ub294 \ubc29\ubc95<\/h3>\n<ol>\n<li>\n<p><strong>\ucffc\ub9ac \uc131\ub2a5 \ucd5c\uc801\ud654:<\/strong> \uce74\ub514\ub110\ub9ac\ud2f0\ub294 \ucffc\ub9ac \ucd5c\uc801\ud654 \ud504\ub85c\uadf8\ub7a8\uc774 \uac00\uc7a5 \ud6a8\uc728\uc801\uc778 \uc2e4\ud589 \uacc4\ud68d\uc744 \uc120\ud0dd\ud558\ub294 \ub370 \ub3c4\uc6c0\uc774 \ub418\uc5b4 \ucffc\ub9ac \uc131\ub2a5\uc774 \ub354 \ube68\ub77c\uc9d1\ub2c8\ub2e4.<\/p>\n<\/li>\n<li>\n<p><strong>\uc9c0\uc218 \uc120\ud0dd:<\/strong> \uce74\ub514\ub110\ub9ac\ud2f0\ub97c \ubd84\uc11d\ud558\uba74 \ub354 \ub098\uc740 \ucffc\ub9ac \uc131\ub2a5\uc744 \uc704\ud574 \uc778\ub371\uc2f1\ud560 \uc5f4\uc5d0 \ub300\ud574 \uc815\ubcf4\uc5d0 \uc785\uac01\ud55c \uacb0\uc815\uc744 \ub0b4\ub9b4 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n<\/li>\n<li>\n<p><strong>\ub370\uc774\ud130 \ud488\uc9c8 \ubd84\uc11d:<\/strong> \uce74\ub514\ub110\ub9ac\ud2f0\ub294 \ub370\uc774\ud130 \uc815\ub9ac \ubc0f \uc720\uc9c0 \uad00\ub9ac\uc5d0 \uc911\uc694\ud560 \uc218 \uc788\ub294 \uc911\ubcf5\ub418\uac70\ub098 \ub204\ub77d\ub41c \ub370\uc774\ud130\ub97c \uc2dd\ubcc4\ud558\ub294 \ub370 \ub3c4\uc6c0\uc774 \ub429\ub2c8\ub2e4.<\/p>\n<\/li>\n<\/ol>\n<h3>SQL\uc758 \uce74\ub514\ub110\ub9ac\ud2f0 \uad00\ub828 \ubb38\uc81c \ubc0f \ud574\uacb0 \ubc29\ubc95<\/h3>\n<ol>\n<li>\n<p><strong>\uc624\ub798\ub41c \ud1b5\uacc4:<\/strong> \uc624\ub798\ub418\uc5c8\uac70\ub098 \ubd80\uc815\ud655\ud55c \ud1b5\uacc4\ub294 \ucd5c\uc801\uc774 \uc544\ub2cc \ucffc\ub9ac \uacc4\ud68d\uc73c\ub85c \uc774\uc5b4\uc9c8 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \uc815\ud655\ud55c \uce74\ub514\ub110\ub9ac\ud2f0 \ucd94\uc815\uc744 \ubcf4\uc7a5\ud558\ub824\uba74 \ub370\uc774\ud130\ubca0\uc774\uc2a4 \ud1b5\uacc4\ub97c \uc815\uae30\uc801\uc73c\ub85c \uc5c5\ub370\uc774\ud2b8\ud558\uc138\uc694.<\/p>\n<\/li>\n<li>\n<p><strong>\ud3b8\ud5a5\ub41c \ub370\uc774\ud130 \ubd84\ud3ec:<\/strong> \ud558\ub098\uc758 \uac12\uc774 \uc5f4\uc744 \uc9c0\ubc30\ud558\ub294 \ud3b8\ud5a5\ub41c \ub370\uc774\ud130 \ubd84\uc0b0\uc740 \ube44\ud6a8\uc728\uc801\uc778 \ucffc\ub9ac \uacc4\ud68d\uc73c\ub85c \uc774\uc5b4\uc9c8 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \uc774\ub7ec\ud55c \uc2dc\ub098\ub9ac\uc624\ub97c \ucc98\ub9ac\ud558\ub824\uba74 \ubd84\ud560\uc774\ub098 \uc778\ub371\uc2f1\uc744 \uace0\ub824\ud558\uc138\uc694.<\/p>\n<\/li>\n<li>\n<p><strong>\ud788\uc2a4\ud1a0\uadf8\ub7a8 \ube48 \ud06c\uae30:<\/strong> \uce74\ub514\ub110\ub9ac\ud2f0 \ucd94\uc815\uc5d0 \uc0ac\uc6a9\ub418\ub294 \ud788\uc2a4\ud1a0\uadf8\ub7a8\uc740 \ube48 \ud06c\uae30\uac00 \ub2e4\ub97c \uc218 \uc788\uc73c\ubbc0\ub85c \uce74\ub514\ub110\ub9ac\ud2f0 \ucd94\uc815\uc774 \ubd80\uc815\ud655\ud574\uc9c8 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \ud788\uc2a4\ud1a0\uadf8\ub7a8 \uc800\uc7a5\uc18c \ud06c\uae30\ub97c \uc870\uc815\ud558\uba74 \uc815\ud655\ub3c4\uac00 \ud5a5\uc0c1\ub420 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n<\/li>\n<\/ol>\n<h2>\uc8fc\uc694 \ud2b9\uc9d5 \ubc0f \uae30\ud0c0 \uc720\uc0ac \uc6a9\uc5b4\uc640\uc758 \ube44\uad50<\/h2>\n<h3>\uce74\ub514\ub110\ub9ac\ud2f0\uc640 \ubc00\ub3c4<\/h3>\n<p>\uce74\ub514\ub110\ub9ac\ud2f0\uc640 \ubc00\ub3c4\ub294 \ucffc\ub9ac \ucd5c\uc801\ud654\uc5d0 \uc0ac\uc6a9\ub418\ub294 \ub450 \uac00\uc9c0 \ud544\uc218 \uac1c\ub150\uc774\uc9c0\ub9cc \uc11c\ub85c \ub2e4\ub978 \ubaa9\uc801\uc73c\ub85c \uc0ac\uc6a9\ub429\ub2c8\ub2e4.<\/p>\n<ul>\n<li>\n<p><strong>\uce74\ub514\ub110\ub9ac\ud2f0<\/strong> \uc5f4\uc774\ub098 \uc778\ub371\uc2a4\uc758 \uace0\uc720 \uac12 \uc218\ub97c \ub098\ud0c0\ub0b4\uba70 \ucffc\ub9ac \ucd5c\uc801\ud654 \ud504\ub85c\uadf8\ub7a8\uc774 \ucffc\ub9ac\uc5d0\uc11c \ubc18\ud658\ub41c \ud589 \uc218\ub97c \ucd94\uc815\ud558\ub294 \ub370 \ub3c4\uc6c0\uc774 \ub429\ub2c8\ub2e4.<\/p>\n<\/li>\n<li>\n<p><strong>\ubc00\ub3c4<\/strong> \uc778\ub371\uc2a4\uc5d0 \uc788\ub294 \ub370\uc774\ud130 \uac12\uc758 \uace0\uc720\uc131\uc744 \ub098\ud0c0\ub0c5\ub2c8\ub2e4. \uc774\ub294 \uce74\ub514\ub110\ub9ac\ud2f0\uc758 \ubc18\ub300\uc774\uba70, \ubb34\uc791\uc704\ub85c \uc120\ud0dd\ud55c \ub450 \ud589\uc774 \uc778\ub371\uc2f1\ub41c \uc5f4\uc5d0 \ub300\ud574 \ub3d9\uc77c\ud55c \uac12\uc744 \uac00\uc9c8 \uac00\ub2a5\uc131\uc744 \ub098\ud0c0\ub0c5\ub2c8\ub2e4.<\/p>\n<\/li>\n<\/ul>\n<p>\uce74\ub514\ub110\ub9ac\ud2f0\uc640 \ubc00\ub3c4\ub294 \ubaa8\ub450 \ucffc\ub9ac \ucd5c\uc801\ud654\uc5d0 \uc601\ud5a5\uc744 \uc8fc\uc9c0\ub9cc \ud6a8\uc728\uc801\uc778 \ucffc\ub9ac \uacc4\ud68d \uc120\ud0dd\uc744 \uc704\ud574 \ucffc\ub9ac \ucd5c\uc801\ud654 \ud504\ub85c\uadf8\ub7a8\uc5d0 \uace0\uc720\ud55c \uc815\ubcf4\ub97c \uc81c\uacf5\ud569\ub2c8\ub2e4.<\/p>\n<h2>Cardinality(SQL)\uc5d0 \ub300\ud55c \ubbf8\ub798\uc758 \uad00\uc810\uacfc \uae30\uc220<\/h2>\n<p>\uae30\uc220\uc774 \ubc1c\uc804\ud558\uace0 \ub370\uc774\ud130\ubca0\uc774\uc2a4\uac00 \ub354\uc6b1 \uc815\uad50\ud574\uc9d0\uc5d0 \ub530\ub77c SQL\uc5d0\uc11c \uce74\ub514\ub110\ub9ac\ud2f0\uc758 \uc911\uc694\uc131\uc740 \uacc4\uc18d\ud574\uc11c \ucee4\uc9c8 \uac83\uc785\ub2c8\ub2e4. \ucffc\ub9ac \ucd5c\uc801\ud654 \uc54c\uace0\ub9ac\uc998\uacfc \uace0\uae09 \ud1b5\uacc4 \uae30\ubc95\uc758 \ud5a5\ud6c4 \uac1c\ubc1c\uc744 \ud1b5\ud574 \uce74\ub514\ub110\ub9ac\ud2f0 \ucd94\uc815\uc758 \uc815\ud655\uc131\uc774 \ub354\uc6b1 \ud5a5\uc0c1\ub420 \uac83\uc73c\ub85c \uc608\uc0c1\ub429\ub2c8\ub2e4. \ub610\ud55c \ud558\ub4dc\uc6e8\uc5b4 \ubc0f \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc544\ud0a4\ud14d\ucc98\uc758 \ubc1c\uc804\uc73c\ub85c \uc778\ud574 \uce74\ub514\ub110\ub9ac\ud2f0 \uacc4\uc0b0\uc774 \ub354\uc6b1 \ud6a8\uc728\uc801\uc73c\ub85c \uc774\ub8e8\uc5b4\uc9c0\uace0 \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc2dc\uc2a4\ud15c\uc758 \uc804\ubc18\uc801\uc778 \uc131\ub2a5\uc774 \ud5a5\uc0c1\ub429\ub2c8\ub2e4.<\/p>\n<h2>\ud504\ub85d\uc2dc \uc11c\ubc84\ub97c \uc0ac\uc6a9\ud558\uac70\ub098 \uce74\ub514\ub110\ub9ac\ud2f0(SQL)\uc640 \uc5f0\uacb0\ud558\ub294 \ubc29\ubc95<\/h2>\n<p>OneProxy\uc5d0\uc11c \uc81c\uacf5\ud558\ub294 \uac83\uacfc \uac19\uc740 \ud504\ub85d\uc2dc \uc11c\ubc84\ub294 \uc6f9 \ub9ac\uc18c\uc2a4\uc5d0 \uc561\uc138\uc2a4\ud560 \ub54c \uac1c\uc778 \uc815\ubcf4 \ubcf4\ud638, \ubcf4\uc548 \ubc0f \uc131\ub2a5\uc744 \ud5a5\uc0c1\uc2dc\ud0a4\ub294 \ub370 \uc911\uc694\ud55c \uc5ed\ud560\uc744 \ud569\ub2c8\ub2e4. SQL\uc758 \uce74\ub514\ub110\ub9ac\ud2f0\uc640 \uc9c1\uc811\uc801\uc778 \uad00\ub828\uc740 \uc5c6\uc9c0\ub9cc \ud504\ub85d\uc2dc \uc11c\ubc84\ub97c \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc560\ud50c\ub9ac\ucf00\uc774\uc158\uacfc \ud568\uaed8 \uc0ac\uc6a9\ud558\uc5ec \ub370\uc774\ud130 \uc561\uc138\uc2a4 \ubc0f \uac00\uc6a9\uc131\uc744 \ud5a5\uc0c1\uc2dc\ud0ac \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n<p>\ud504\ub85d\uc2dc \uc11c\ubc84\ub294 \uc790\uc8fc \uc561\uc138\uc2a4\ud558\ub294 \ub370\uc774\ud130\ubca0\uc774\uc2a4 \ub9ac\uc18c\uc2a4\ub97c \uce90\uc2dc\ud558\uc5ec \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc11c\ubc84\uc5d0 \ub3c4\ub2ec\ud558\ub294 \uc694\uccad \uc218\ub97c \uc904\uc774\uace0 \uc7a0\uc7ac\uc801\uc73c\ub85c \uc751\ub2f5 \uc2dc\uac04\uc744 \ud5a5\uc0c1\uc2dc\ud0ac \uc218 \uc788\uc2b5\ub2c8\ub2e4. \ub610\ud55c \ud504\ub85d\uc2dc \uc11c\ubc84\ub294 \ud074\ub77c\uc774\uc5b8\ud2b8\uc640 \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc0ac\uc774\uc758 \uc911\uac1c\uc790 \uc5ed\ud560\uc744 \ud558\uc5ec \ucd94\uac00 \ubcf4\uc548 \uacc4\uce35\uacfc \ub85c\ub4dc \ubc38\ub7f0\uc2f1\uc744 \ucd94\uac00\ud560 \uc218 \uc788\uc73c\uba70 \uc774\ub294 \ud2b8\ub798\ud53d\uc774 \ub9ce\uc740 \uc2dc\ub098\ub9ac\uc624\uc5d0\uc11c \ud2b9\ud788 \uc720\uc6a9\ud560 \uc218 \uc788\uc2b5\ub2c8\ub2e4.<\/p>\n<h2>\uad00\ub828\ub41c \ub9c1\ud06c\ub4e4<\/h2>\n<p>SQL\uc758 \uce74\ub514\ub110\ub9ac\ud2f0\uc5d0 \ub300\ud55c \uc790\uc138\ud55c \ub0b4\uc6a9\uc744 \ubcf4\ub824\uba74 \ub2e4\uc74c \ub9ac\uc18c\uc2a4\ub97c \ucc38\uc870\ud558\uc138\uc694.<\/p>\n<ul>\n<li><a href=\"https:\/\/docs.microsoft.com\/en-us\/previous-versions\/sql\/sql-server-2008\/dd535534(v=sql.100)\" target=\"_new\" rel=\"noopener nofollow\">SQL Server \uce74\ub514\ub110\ub9ac\ud2f0 \ucd94\uc815 \uc774\ud574<\/a><\/li>\n<li><a href=\"https:\/\/www.postgresql.org\/docs\/current\/planner-stats.html\" target=\"_new\" rel=\"noopener nofollow\">PostgreSQL\uc758 \uce74\ub514\ub110\ub9ac\ud2f0 \ucd94\uc815<\/a><\/li>\n<li><a href=\"https:\/\/dev.mysql.com\/doc\/mysql\/en\/query-optimization.html\" target=\"_new\" rel=\"noopener nofollow\">MySQL \ucffc\ub9ac \ucd5c\uc801\ud654 \ubc0f \uce74\ub514\ub110\ub9ac\ud2f0<\/a><\/li>\n<\/ul>\n<p>\ub370\uc774\ud130\ubca0\uc774\uc2a4 \uc131\ub2a5\uc744 \ucd5c\uc801\ud654\ud558\uace0 \ud6a8\uc728\uc801\uc778 \ucffc\ub9ac \uc2e4\ud589\uc744 \ubcf4\uc7a5\ud558\ub824\uba74 \uce74\ub514\ub110\ub9ac\ud2f0\ub97c \uc774\ud574\ud558\ub294 \uac83\uc774 \uc911\uc694\ud569\ub2c8\ub2e4. \ub370\uc774\ud130\ubca0\uc774\uc2a4 \uae30\uc220\uc758 \ucd5c\uc2e0 \uac1c\ubc1c \uc0c1\ud669\uc744 \ud30c\uc545\ud558\uba74 \uc815\ubcf4\uc5d0 \uc785\uac01\ud55c \uacb0\uc815\uc744 \ub0b4\ub9ac\uace0 \ub370\uc774\ud130 \uae30\ubc18 \uc560\ud50c\ub9ac\ucf00\uc774\uc158\uc758 \uc7a0\uc7ac\ub825\uc744 \ucd5c\ub300\ud55c \ud65c\uc6a9\ud560 \uc218 \uc788\ub294 \uc5ed\ub7c9\uc774 \ub354\uc6b1 \uac15\ud654\ub429\ub2c8\ub2e4.<\/p>","protected":false},"featured_media":467828,"menu_order":0,"template":"","meta":{"_acf_changed":false,"content-type":"","inline_featured_image":false,"footnotes":""},"class_list":["post-476178","wiki","type-wiki","status-publish","has-post-thumbnail","hentry"],"acf":{"faq_title":"Frequently Asked Questions about <mark>Cardinality (SQL)<\/mark>","faq_items":[{"question":"What is Cardinality in SQL?","answer":"<p>Cardinality in SQL refers to the number of distinct values present in a column or index of a database table. It helps the database engine optimize queries and make efficient execution plans.<\/p>"},{"question":"How does Cardinality work in SQL?","answer":"<p>Cardinality is maintained within the database statistics, which store information about the number of rows, distinct values, and data distribution. The query optimizer uses this information to estimate the number of rows returned by a query and choose the best execution plan.<\/p>"},{"question":"What are the types of Cardinality in SQL?","answer":"<p>There are three primary types of Cardinality:<\/p><ol><li>Low Cardinality: Few distinct values, often seen in columns like gender or country.<\/li><li>Medium Cardinality: Moderate distinct values, falling between low and high Cardinality.<\/li><li>High Cardinality: Many distinct values, common in primary key or unique identifier columns.<\/li><\/ol>"},{"question":"How can I use Cardinality in SQL?","answer":"<p>Cardinality is essential for:<\/p><ul><li>Optimizing query performance<\/li><li>Selecting appropriate indexes for better performance<\/li><li>Identifying data quality issues like duplicates or missing data<\/li><\/ul>"},{"question":"What are the challenges related to Cardinality in SQL?","answer":"<p>Problems related to Cardinality include outdated statistics, skewed data distribution, and inaccurate histogram bin sizes. Regularly updating statistics and considering partitioning or indexing can address these challenges.<\/p>"},{"question":"How is Cardinality different from Density in SQL?","answer":"<p>Cardinality represents the number of distinct values, while Density indicates the uniqueness of data values in an index. Both impact query optimization but serve different purposes.<\/p>"},{"question":"What is the future perspective of Cardinality in SQL?","answer":"<p>As technology advances, Cardinality's importance will continue to grow, leading to more accurate estimations and efficient query plans. Advancements in hardware and database architecture will further improve Cardinality computations and overall database performance.<\/p>"},{"question":"How can proxy servers be associated with Cardinality in SQL?","answer":"<p>While not directly related, proxy servers can work with database applications to improve data access and availability. They can cache frequently accessed resources, add security layers, and perform load balancing for high-traffic scenarios.<\/p>"}]},"_links":{"self":[{"href":"https:\/\/oneproxy.pro\/kr\/wp-json\/wp\/v2\/wiki\/476178","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/oneproxy.pro\/kr\/wp-json\/wp\/v2\/wiki"}],"about":[{"href":"https:\/\/oneproxy.pro\/kr\/wp-json\/wp\/v2\/types\/wiki"}],"version-history":[{"count":0,"href":"https:\/\/oneproxy.pro\/kr\/wp-json\/wp\/v2\/wiki\/476178\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/oneproxy.pro\/kr\/wp-json\/wp\/v2\/media\/467828"}],"wp:attachment":[{"href":"https:\/\/oneproxy.pro\/kr\/wp-json\/wp\/v2\/media?parent=476178"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}