{"id":464,"date":"2012-01-09T23:57:27","date_gmt":"2012-01-09T15:57:27","guid":{"rendered":"https:\/\/yangtingkun.net\/?p=464"},"modified":"2012-01-10T10:11:26","modified_gmt":"2012-01-10T02:11:26","slug":"date%e7%b1%bb%e5%9e%8b%e6%88%aa%e5%8f%96%e5%88%b0%e5%a4%a9%e7%9a%84%e6%95%88%e7%8e%87","status":"publish","type":"post","link":"https:\/\/yangtingkun.net\/?p=464","title":{"rendered":"DATE\u7c7b\u578b\u622a\u53d6\u5230\u5929\u7684\u6548\u7387"},"content":{"rendered":"<p>\u5728ITPUB\u4e0a\u770b\u4e86\u4e00\u4e2a\u5e16\u5b50\uff0c\u6839\u636e\u65e5\u671f\u7c7b\u578b\u5bf9\u6bcf\u5929\u7684\u8bb0\u5f55\u8fdb\u884cGROUP BY\uff0c\u5e16\u5b50\u7684\u5730\u5740\u5982\u4e0b\uff1a<a href=\"http:\/\/www.itpub.net\/thread-1564295-1-1.html\">http:\/\/www.itpub.net\/thread-1564295-1-1.html<\/a><br \/>\n\u8fd9\u79cd\u5305\u542b\u5168\u8868\u626b\u63cf\u6267\u884cGROUP BY\u7684\u8bed\u53e5\u662f\u5426\u8fd8\u6709\u4f18\u5316\u7684\u4f59\u5730\u5417\uff0c\u4e8b\u5b9e\u4e0a\u786e\u5b9e\u8fd8\u6709\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u5904\u7406\u65e5\u671f\u7c7b\u578b\uff0cTO_CHAR\u5e76\u6ca1\u6709TRUNC\u9ad8\u6548\u3002<br \/>\n\u4e0b\u9762\u770b\u4e00\u4e2a\u7b80\u5355\u7684\u4f8b\u5b50\uff1a<\/p>\n<pre lang='SQL'>SQL> CREATE TABLE T_DATE AS\r\n  2  SELECT ROWNUM ID, CREATED \r\n  3  FROM DBA_OBJECTS A, (SELECT 1 FROM DUAL CONNECT BY ROWNUM < 100)  \r\n  4  WHERE ROWNUM <= 1000000;\r\nTable created.\r\nSQL> SELECT COUNT(*) FROM T_DATE;\r\n  COUNT(*)\r\n----------\r\n   1000000\r\nSQL> SET TIMING ON\r\nSQL> SELECT TO_CHAR(CREATED, 'YYYY-MM-DD'), COUNT(*) \r\n  2  FROM T_DATE \r\n  3  GROUP BY TO_CHAR(CREATED, 'YYYY-MM-DD');\r\nTO_CHAR(CR   COUNT(*)\r\n---------- ----------\r\n2012-01-07       3600\r\n2012-01-08       3750\r\n2012-01-09       4650\r\n2012-01-06     987925\r\n2012-01-10         75\r\nElapsed: 00:00:00.46\r\nSQL> SELECT TO_CHAR(CREATED, 'YYYY-MM-DD'), COUNT(*) \r\n  2  FROM T_DATE \r\n  3  GROUP BY TO_CHAR(CREATED, 'YYYY-MM-DD');\r\nTO_CHAR(CR   COUNT(*)\r\n---------- ----------\r\n2012-01-07       3600\r\n2012-01-08       3750\r\n2012-01-09       4650\r\n2012-01-06     987925\r\n2012-01-10         75\r\nElapsed: 00:00:00.40\r\nSQL> SELECT TO_CHAR(CREATED, 'YYYY-MM-DD'), COUNT(*) \r\n  2  FROM T_DATE \r\n  3  GROUP BY TO_CHAR(CREATED, 'YYYY-MM-DD');\r\nTO_CHAR(CR   COUNT(*)\r\n---------- ----------\r\n2012-01-07       3600\r\n2012-01-08       3750\r\n2012-01-09       4650\r\n2012-01-06     987925\r\n2012-01-10         75\r\nElapsed: 00:00:00.39\r\nSQL> SELECT TO_CHAR(CREATED, 'YYYY-MM-DD'), COUNT(*) \r\n  2  FROM T_DATE \r\n  3  GROUP BY TO_CHAR(CREATED, 'YYYY-MM-DD');\r\nTO_CHAR(CR   COUNT(*)\r\n---------- ----------\r\n2012-01-07       3600\r\n2012-01-08       3750\r\n2012-01-09       4650\r\n2012-01-06     987925\r\n2012-01-10         75\r\nElapsed: 00:00:00.44\r\nSQL> SELECT TO_CHAR(TRUNC(CREATED), 'YYYY-MM-DD'), COUNT(*) \r\n  2  FROM T_DATE \r\n  3  GROUP BY TRUNC(CREATED);\r\nTO_CHAR(TR   COUNT(*)\r\n---------- ----------\r\n2012-01-06     987925\r\n2012-01-10         75\r\n2012-01-08       3750\r\n2012-01-07       3600\r\n2012-01-09       4650\r\nElapsed: 00:00:00.36\r\nSQL> SELECT TO_CHAR(TRUNC(CREATED), 'YYYY-MM-DD'), COUNT(*) \r\n  2  FROM T_DATE \r\n  3  GROUP BY TRUNC(CREATED);\r\nTO_CHAR(TR   COUNT(*)\r\n---------- ----------\r\n2012-01-10         75\r\n2012-01-07       3600\r\n2012-01-09       4650\r\n2012-01-06     987925\r\n2012-01-08       3750\r\nElapsed: 00:00:00.35\r\nSQL> SELECT TO_CHAR(TRUNC(CREATED), 'YYYY-MM-DD'), COUNT(*) \r\n  2  FROM T_DATE \r\n  3  GROUP BY TRUNC(CREATED);\r\nTO_CHAR(TR   COUNT(*)\r\n---------- ----------\r\n2012-01-10         75\r\n2012-01-07       3600\r\n2012-01-09       4650\r\n2012-01-06     987925\r\n2012-01-08       3750\r\nElapsed: 00:00:00.36\r\nSQL> SELECT TO_CHAR(TRUNC(CREATED), 'YYYY-MM-DD'), COUNT(*) \r\n  2  FROM T_DATE \r\n  3  GROUP BY TRUNC(CREATED);\r\nTO_CHAR(TR   COUNT(*)\r\n---------- ----------\r\n2012-01-10         75\r\n2012-01-07       3600\r\n2012-01-09       4650\r\n2012-01-06     987925\r\n2012-01-08       3750\r\nElapsed: 00:00:00.34<\/pre>\n<p>\u5982\u679c\u4ec5\u4ece\u6267\u884c\u8ba1\u5212\u548c\u903b\u8f91\u8bfb\u4e0a\u8fdb\u884c\u5206\u6790\uff0c\u4e24\u4e2aSQL\u6ca1\u6709\u4efb\u4f55\u533a\u522b\uff1a<\/p>\n<pre lang='SQL'>SQL> set autot on\r\nSQL> SELECT TO_CHAR(CREATED, 'YYYY-MM-DD'), COUNT(*) \r\n  2  FROM T_DATE \r\n  3  GROUP BY TO_CHAR(CREATED, 'YYYY-MM-DD');\r\nTO_CHAR(CR   COUNT(*)\r\n---------- ----------\r\n2012-01-07       3600\r\n2012-01-08       3750\r\n2012-01-09       4650\r\n2012-01-06     987925\r\n2012-01-10         75\r\nElapsed: 00:00:00.43\r\nExecution Plan\r\n----------------------------------------------------------\r\nPlan hash value: 534547868\r\n-----------------------------------------------------------------------------\r\n| Id  | Operation          | Name   | Rows  | Bytes | Cost (%CPU)| Time     |\r\n-----------------------------------------------------------------------------\r\n|   0 | SELECT STATEMENT   |        |  1294K|    11M|   726   (6)| 00:00:09 |\r\n|   1 |  HASH GROUP BY     |        |  1294K|    11M|   726   (6)| 00:00:09 |\r\n|   2 |   TABLE ACCESS FULL| T_DATE |  1294K|    11M|   694   (1)| 00:00:09 |\r\n-----------------------------------------------------------------------------\r\nNote\r\n-----\r\n   - dynamic sampling used for this statement (level=2)\r\nStatistics\r\n----------------------------------------------------------\r\n          0  recursive calls\r\n          0  db block gets\r\n       2490  consistent gets\r\n       2487  physical reads\r\n          0  redo size\r\n        754  bytes sent via SQL*Net to client\r\n        524  bytes received via SQL*Net from client\r\n          2  SQL*Net roundtrips to\/from client\r\n          0  sorts (memory)\r\n          0  sorts (disk)\r\n          5  rows processed\r\nSQL> SELECT TO_CHAR(TRUNC(CREATED), 'YYYY-MM-DD'), COUNT(*) \r\n  2  FROM T_DATE \r\n  3  GROUP BY TRUNC(CREATED);\r\nTO_CHAR(TR   COUNT(*)\r\n---------- ----------\r\n2012-01-10         75\r\n2012-01-07       3600\r\n2012-01-09       4650\r\n2012-01-06     987925\r\n2012-01-08       3750\r\nElapsed: 00:00:00.34\r\nExecution Plan\r\n----------------------------------------------------------\r\nPlan hash value: 534547868\r\n-----------------------------------------------------------------------------\r\n| Id  | Operation          | Name   | Rows  | Bytes | Cost (%CPU)| Time     |\r\n-----------------------------------------------------------------------------\r\n|   0 | SELECT STATEMENT   |        |  1294K|    11M|   726   (6)| 00:00:09 |\r\n|   1 |  HASH GROUP BY     |        |  1294K|    11M|   726   (6)| 00:00:09 |\r\n|   2 |   TABLE ACCESS FULL| T_DATE |  1294K|    11M|   694   (1)| 00:00:09 |\r\n-----------------------------------------------------------------------------\r\nNote\r\n-----\r\n   - dynamic sampling used for this statement (level=2)\r\nStatistics\r\n----------------------------------------------------------\r\n          0  recursive calls\r\n          0  db block gets\r\n       2490  consistent gets\r\n       2487  physical reads\r\n          0  redo size\r\n        761  bytes sent via SQL*Net to client\r\n        524  bytes received via SQL*Net from client\r\n          2  SQL*Net roundtrips to\/from client\r\n          0  sorts (memory)\r\n          0  sorts (disk)\r\n          5  rows processed<\/pre>\n<p>\u4f46\u662f\u89c2\u5bdf\u4e24\u4e2aSQL\u7684\u5e73\u5747\u6267\u884c\u65f6\u95f4\uff0c\u4f1a\u53d1\u73b0\u4f7f\u7528TRUNC\u65b9\u5f0f\u6bd4TO_CHAR\u67091\/8\u7684\u6027\u80fd\u63d0\u5347\uff0c\u5bf9\u4e8e\u6267\u884c\u8ba1\u5212\u5b8c\u5168\u76f8\u540c\u7684\u60c5\u51b5\u800c\u8a00\uff0c\u8fd9\u4e2a\u6bd4\u7387\u5df2\u7ecf\u5f88\u9ad8\u4e86\u3002<br \/>\n\u5176\u5b9e\u5bfc\u81f4\u95ee\u9898\u7684\u539f\u56e0\u5728\u4e8eDATE\u7c7b\u578b\u7684\u5b58\u50a8\uff0cDATE\u75317\u4e2a\u5b57\u8282\u7ec4\u6210\uff0c\u5206\u522b\u4e3a\u4e16\u7eaa\u3001\u5e74\u3001\u6708\u3001\u65e5\u3001\u65f6\u3001\u5206\u3001\u79d2\u3002\u5bf9\u4e8eTRUNC\u51fd\u6570\u800c\u8a00\uff0c\u53ea\u662f\u7b80\u5355\u7684\u820d\u5f03\u6389\u540e\u9762\u4e09\u4e2a\u5b57\u8282\uff0c\u56e0\u6b64\u6548\u7387\u6700\u9ad8\uff0c\u800cTO_CHAR\u9700\u8981\u5c06\u5185\u90e8\u7684\u5b58\u50a8\u683c\u5f0f\u8f6c\u5316\u4e3a\u5b57\u7b26\u683c\u5f0f\uff0c\u663e\u7136\u4f1a\u6d88\u8017\u66f4\u591a\u7684\u8d44\u6e90\u3002<br \/>\n\u4e24\u4e2aSQL\u8fd4\u56de\u7ed3\u679c\u987a\u5e8f\u7684\u4e0d\u540c\u4e5f\u8bf4\u660e\u4e86\u8fd9\u4e00\u70b9\uff0cTRUNC\u51fd\u6570\u8fdb\u884cHASH GROUP\u7684\u662f\u65e5\u671f\u683c\u5f0f\uff0c\u800cTO_CHAR\u51fd\u6570\u8fdb\u884cHASH GROUP\u7684\u662f\u5b57\u7b26\u7c7b\u578b\uff0c\u5bfc\u81f4\u4e86\u6700\u7ec8\u7ed3\u679c\u8fd4\u56de\u987a\u5e8f\u7684\u5dee\u5f02\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5728ITPUB\u4e0a\u770b\u4e86\u4e00\u4e2a\u5e16\u5b50\uff0c\u6839\u636e\u65e5\u671f\u7c7b\u578b\u5bf9\u6bcf\u5929\u7684\u8bb0\u5f55\u8fdb\u884cGROUP BY\uff0c\u5e16\u5b50\u7684\u5730\u5740\u5982\u4e0b\uff1ahttp:\/\/www.itpub.net\/thread-1564295-1-1.html \u8fd9\u79cd\u5305\u542b\u5168\u8868\u626b\u63cf\u6267\u884cGROUP BY\u7684\u8bed\u53e5\u662f\u5426\u8fd8\u6709\u4f18\u5316\u7684\u4f59\u5730\u5417\uff0c\u4e8b\u5b9e\u4e0a\u786e\u5b9e\u8fd8\u6709\uff0c\u56e0\u4e3a\u5bf9\u4e8e\u5904\u7406\u65e5\u671f\u7c7b\u578b\uff0cTO_CHAR\u5e76\u6ca1\u6709TRUNC\u9ad8\u6548\u3002 \u4e0b\u9762\u770b\u4e00\u4e2a\u7b80\u5355\u7684\u4f8b\u5b50\uff1a SQL> CREATE TABLE T_DATE AS 2 SELECT ROWNUM ID, CREATED 3 FROM DBA_OBJECTS A, (SELECT 1 FROM DUAL CONNECT BY ROWNUM < 100) 4 WHERE ROWNUM SELECT COUNT(*) FROM T_DATE; COUNT(*) ---------- 1000000 SQL> SET &hellip; <a href=\"https:\/\/yangtingkun.net\/?p=464\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[3],"tags":[363,364,362],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p2yiY3-7u","_links":{"self":[{"href":"https:\/\/yangtingkun.net\/index.php?rest_route=\/wp\/v2\/posts\/464"}],"collection":[{"href":"https:\/\/yangtingkun.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/yangtingkun.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/yangtingkun.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/yangtingkun.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=464"}],"version-history":[{"count":2,"href":"https:\/\/yangtingkun.net\/index.php?rest_route=\/wp\/v2\/posts\/464\/revisions"}],"predecessor-version":[{"id":466,"href":"https:\/\/yangtingkun.net\/index.php?rest_route=\/wp\/v2\/posts\/464\/revisions\/466"}],"wp:attachment":[{"href":"https:\/\/yangtingkun.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=464"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/yangtingkun.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=464"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/yangtingkun.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=464"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}