{"id":359,"date":"2023-02-23T11:37:35","date_gmt":"2023-02-23T03:37:35","guid":{"rendered":"https:\/\/xinchewhd.com.cn\/?p=359"},"modified":"2023-05-28T01:24:37","modified_gmt":"2023-05-27T17:24:37","slug":"sql-%e4%bc%98%e5%8c%96%e5%ae%9e%e8%b7%b5","status":"publish","type":"post","link":"https:\/\/xinchewhd.com.cn\/index.php\/mysql\/sql-%e4%bc%98%e5%8c%96%e5%ae%9e%e8%b7%b5\/","title":{"rendered":"SQL \u4f18\u5316\u5b9e\u8df5"},"content":{"rendered":"
\n

\u5de5\u4f5c\u4e2d\u9700\u8981\u6ce8\u610f\u7684 SQL \u8bed\u53e5\u4f18\u5316\u70b9\uff0cSQL \u4f18\u5316\u9996\u5148\u8981\u5bf9 SQL \u7684\u6d88\u8017\u65f6\u95f4\u6216\u8005\u4f7f\u7528\u9891\u7387\u8fdb\u884c\u5206\u6790\uff0c\u7136\u540e\u518d\u8fdb\u884c\u5176\u4ed6\u64cd\u4f5c\u3002<\/p>\n

SQL \u4f18\u5316\u7684\u65b9\u5f0f<\/span><\/h2>\n

1\u3001SQL \u7684\u6267\u884c\u6b21\u6570\u5206\u6790<\/strong><\/p>\n

show<\/span>\u00a0global<\/span>\u00a0status<\/span>\u00a0like<\/span>\u00a0'com_______'<\/span>;\u00a0
<\/code><\/pre>\n
\u901a\u8fc7\u8be5\u547d\u4ee4\u53ef\u4ee5\u67e5\u770b\u5f53\u524d\u6570\u636e\u5e93\u4e0b\u7684\u589e\u5220\u6539\u67e5\u7684\u4f7f\u7528\u6b21\u6570\uff0c\u6765\u91c7\u53d6\u5bf9\u5e94\u7684\u4f18\u5316\u5904\u7406\uff0c value \u503c\u5c31\u662f\u6267\u884c\u7684\u6b21\u6570\u3002<\/p>\n
2\u3001\u6162\u67e5\u8be2\u65e5\u5fd7<\/strong><\/p>\n
show<\/span>\u00a0variables<\/span>\u00a0like<\/span>\u00a0'%slow_query_log%'<\/span>;
<\/code><\/pre>\n
\u6162\u67e5\u8be2\u65e5\u5fd7\u4f1a\u8bb0\u5f55\u8d85\u51fa\u81ea\u5df1\u8bbe\u7f6e\u7684\u65f6\u95f4\u8fd8\u6ca1\u6709\u6267\u884c\u5b8c\u6bd5\u7684 sql\u3002<\/p>\n
\u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0cMysql \u6570\u636e\u5e93\u5e76\u4e0d\u542f\u52a8\u6162\u67e5\u8be2\u65e5\u5fd7\uff0c\u9700\u8981\u6211\u4eec\u624b\u52a8\u6765\u8bbe\u7f6e\u8fd9\u4e2a\u53c2\u6570\uff0c\u5982\u679c\u4e0d\u662f\u8c03\u4f18\u9700\u8981\u7684\u8bdd\uff0c\u4e00\u822c\u4e0d\u5efa\u8bae\u542f\u52a8\u8be5\u53c2\u6570\uff0c\u56e0\u4e3a\u5f00\u542f\u6162\u67e5\u8be2\u65e5\u5fd7\u4f1a\u6216\u591a\u6216\u5c11\u5e26\u6765\u4e00\u5b9a\u7684\u6027\u80fd\u5f71\u54cd\u3002<\/p>\n
\u6162\u67e5\u8be2\u65e5\u5fd7\u652f\u6301\u5c06\u65e5\u5fd7\u8bb0\u5f55\u5199\u5165\u6587\u4ef6\uff0c\u4e5f\u652f\u6301\u5c06\u65e5\u5fd7\u8bb0\u5f55\u5199\u5165\u6570\u636e\u5e93\u8868\u3002<\/p>\n
\u5f00\u542f\u6162\u67e5\u8be2\u65e5\u5fd7 sql\uff1a<\/p>\n
set<\/span>\u00a0global<\/span>\u00a0slow_query_log=1<\/span>;
<\/code><\/pre>\n
\u8bbe\u7f6e\u6162\u67e5\u8be2\u7684\u8d85\u65f6\u65f6\u95f4:<\/p>\n
set<\/span>\u00a0global<\/span>\u00a0long_query_time=2<\/span>;\u00a0--\u00a0\u4ee5\u79d2\u4e3a\u5355\u4f4d<\/span>
<\/code><\/pre>\n
\n
\u6ce8\u610f\uff1a\u4f7f\u7528\u00a0set global slow_query_log=1<\/code>\u00a0\u5f00\u542f\u4e86\u6162\u67e5\u8be2\u65e5\u5fd7\u53ea\u5bf9\u5f53\u524d\u6570\u636e\u5e93\u751f\u6548\uff0cMySQL \u91cd\u542f\u540e\u5219\u4f1a\u5931\u6548\u3002\u5982\u679c\u8981\u6c38\u4e45\u751f\u6548\uff0c\u5c31\u5fc5\u987b\u4fee\u6539\u914d\u7f6e\u6587\u4ef6\u00a0my.cnf<\/code>\u3002<\/p>\n<\/blockquote>\n
3\u3001profile \u5206\u6790<\/strong><\/p>\n
3.1\u3001\u5f00\u542f profile:<\/p>\n
SET<\/span>\u00a0profiling\u00a0=\u00a01<\/span>;
<\/code><\/pre>\n
3.2\u3001\u67e5\u770b\u5f53\u524d\u4f1a\u8bdd\u4e0b\u7684\u6240\u6709 sql \u6267\u884c\u65f6\u95f4:<\/p>\n
show<\/span>\u00a0profiles<\/span>;
<\/code><\/pre>\n
3.3\u3001\u67e5\u770b\u5177\u4f53 sql \u7684\u6bcf\u4e2a\u6b65\u9aa4\u6d88\u8017\u65f6\u95f4:<\/p>\n
show<\/span>\u00a0profiles<\/span>\u00a0for<\/span>\u00a0query<\/span>\u00a0\u00a0xx;\u00a0\u00a0\u00a0--\u00a0\u8fd9\u4e2axx\u662f\u00a0`show\u00a0profiles`\u00a0\u7ed3\u679c\u7684\u00a0query_id<\/span>
<\/code><\/pre>\n
\n
\u6ce8\u610f\uff1aprofile \u662f\u7528\u6237\u7ea7\u53d8\u91cf\uff0c\u6bcf\u6b21\u90fd\u5f97\u91cd\u65b0\u542f\u7528\u3002<\/p>\n<\/blockquote>\n
3.4\u3001\u67e5\u770b\u5177\u4f53 sql \u7684 cpu \u6d88\u8017\u65f6\u95f4\uff1a<\/p>\n
show<\/span>\u00a0profiles<\/span>\u00a0cpu\u00a0\u00a0for<\/span>\u00a0query<\/span>\u00a0\u00a0xx;\u00a0--\u00a0\u6bd4\u4e0a\u4e2a\u6b65\u9aa4\u591a\u4e86\u4e00\u4e2acpu\u5b57\u6bb5<\/span>
<\/code><\/pre>\n
explain \u5173\u952e\u5b57<\/span><\/h2>\n
explain \u662f\u975e\u5e38\u91cd\u8981\u7684\u5173\u952e\u5b57\uff0c\u8981\u5584\u4e8e\u8fd0\u7528\u5b83\uff0c\u901a\u8fc7 explain \u53ef\u4ee5\u83b7\u5f97\u4ee5\u4e0b\u4fe1\u606f\uff1a<\/p>\n
    \n
  • \n
    \u8868\u7684\u8bfb\u53d6\u987a\u5e8f<\/section>\n<\/li>\n
  • \n
    \u6570\u636e\u8bfb\u53d6\u64cd\u4f5c\u7684\u64cd\u4f5c\u7c7b\u578b<\/section>\n<\/li>\n
  • \n
    \u54ea\u4e9b\u7d22\u5f15\u53ef\u4ee5\u4f7f\u7528<\/section>\n<\/li>\n
  • \n
    \u54ea\u4e9b\u7d22\u5f15\u88ab\u5b9e\u9645\u4f7f\u7528<\/section>\n<\/li>\n
  • \n
    \u8868\u4e4b\u95f4\u7684\u5f15\u7528<\/section>\n<\/li>\n
  • \n
    \u6bcf\u5f20\u8868\u6709\u591a\u5c11\u884c\u88ab\u4f18\u5316\u5668\u67e5\u8be2<\/section>\n<\/li>\n<\/ul>\n
    explain<\/span>\u00a0select<\/span>\u00a0*\u00a0from<\/span>\u00a0table<\/span>;\u00a0--\u00a0explain\u00a0+\u00a0sql\u00a0\u8bed\u53e5<\/span>
    <\/code><\/pre>\n
    explain \u67e5\u8be2\u7684\u7ed3\u679c\u5305\u542b\u7684\u5b57\u6bb5:<\/p>\n
    \n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
    \u5b57\u6bb5<\/th>\n\u63cf\u8ff0<\/th>\n<\/tr>\n<\/thead>\n
    id<\/td>\n\u67e5\u8be2\u7684\u5e8f\u53f7\uff0c\u5305\u542b\u4e00\u7ec4\u6570\u5b57\uff0c\u8868\u793a\u67e5\u8be2\u4e2d\u6267\u884c select \u5b50\u53e5\u6216\u64cd\u4f5c\u8868\u7684\u987a\u5e8f\u3002\u6709\u4e24\u79cd\u60c5\u51b5\uff1a
    1.id \u76f8\u540c<\/code>\uff1a\u6267\u884c\u987a\u5e8f\u4ece\u4e0a\u5f80\u4e0b\uff1b
    2.id \u4e0d\u540c<\/code>\uff1aid \u503c\u8d8a\u5927\uff0c\u4f18\u5148\u7ea7\u8d8a\u9ad8\uff0c\u8d8a\u5148\u6267\u884c\u3002<\/td>\n<\/tr>\n
    select_type<\/td>\n\u67e5\u8be2\u7c7b\u578b\uff0c\u4e3b\u8981\u7528\u4e8e\u533a\u522b\u666e\u901a\u67e5\u8be2\uff0c\u8054\u5408\u67e5\u8be2\uff0c\u5b50\u67e5\u8be2\u7b49\u7684\u590d\u6742\u67e5\u8be2
    1.simple<\/code>\uff1a\u7b80\u5355\u7684 select \u67e5\u8be2\uff0c\u67e5\u8be2\u4e2d\u4e0d\u5305\u542b\u5b50\u67e5\u8be2\u6216\u8005 UNION\uff1b
    2.primary<\/code>\uff1a\u67e5\u8be2\u4e2d\u82e5\u5305\u542b\u4efb\u4f55\u590d\u6742\u7684\u5b50\u90e8\u5206\uff0c\u6700\u5916\u5c42\u67e5\u8be2\u88ab\u6807\u8bb0\uff1b
    3.subquery<\/code>\uff1a\u5728 select \u6216 where \u5217\u8868\u4e2d\u5305\u542b\u4e86\u5b50\u67e5\u8be2\uff1b
    4.derived<\/code>\uff1a\u5728 from \u5217\u8868\u4e2d\u5305\u542b\u7684\u5b50\u67e5\u8be2\u88ab\u6807\u8bb0\u4e3a derived\uff08\u884d\u751f\uff09\uff0cMySQL \u4f1a\u9012\u5f52\u6267\u884c\u8fd9\u4e9b\u5b50\u67e5\u8be2\uff0c\u628a\u7ed3\u679c\u653e\u5230\u4e34\u65f6\u8868\u4e2d\uff1b
    5.union<\/code>\uff1a\u5982\u679c\u7b2c\u4e8c\u4e2a select \u51fa\u73b0\u5728 UNION \u4e4b\u540e\uff0c\u5219\u88ab\u6807\u8bb0\u4e3a UNION\uff0c\u5982\u679c union \u5305\u542b\u5728 from \u5b50\u53e5\u7684\u5b50\u67e5\u8be2\u4e2d\uff0c\u5916\u5c42 select \u88ab\u6807\u8bb0\u4e3a derived\uff1b
    6.union result<\/code>\uff1aUNION \u7684\u7ed3\u679c\u3002<\/td>\n<\/tr>\n
    table<\/td>\n\u8f93\u51fa\u7684\u884c\u6240\u5f15\u7528\u7684\u8868<\/td>\n<\/tr>\n
    type<\/td>\n\u663e\u793a\u8fde\u7ed3\u7c7b\u578b\uff0c\u663e\u793a\u67e5\u8be2\u4f7f\u7528\u4e86\u4f55\u79cd\u7c7b\u578b\uff0c\u6309\u7167\u4ece\u6700\u4f73\u5230\u6700\u574f\u7c7b\u578b\u6392\u5e8f
    1.system<\/code>\uff1a\u8868\u4e2d\u4ec5\u6709\u4e00\u884c\uff08=\u7cfb\u7edf\u8868\uff09\u8fd9\u662f const \u8054\u7ed3\u7c7b\u578b\u7684\u4e00\u4e2a\u7279\u4f8b\uff1b
    2.const<\/code>\uff1a\u8868\u793a\u901a\u8fc7\u7d22\u5f15\u4e00\u6b21\u5c31\u627e\u5230\uff0cconst \u7528\u4e8e\u6bd4\u8f83 primary key \u6216\u8005 unique \u7d22\u5f15\u3002\u56e0\u4e3a\u53ea\u5339\u914d\u4e00\u884c\u6570\u636e\uff0c\u6240\u4ee5\u5982\u679c\u5c06\u4e3b\u952e\u7f6e\u4e8e where \u5217\u8868\u4e2d\uff0cmysql \u80fd\u5c06\u8be5\u67e5\u8be2\u8f6c\u6362\u4e3a\u4e00\u4e2a\u5e38\u91cf\uff1b
    3.eq_ref<\/code>\uff1a\u552f\u4e00\u6027\u7d22\u5f15\u626b\u63cf\uff0c\u5bf9\u4e8e\u6bcf\u4e2a\u7d22\u5f15\u952e\uff0c\u8868\u4e2d\u53ea\u6709\u4e00\u6761\u8bb0\u5f55\u4e0e\u4e4b\u5339\u914d\u3002\u5e38\u89c1\u4e8e\u552f\u4e00\u7d22\u5f15\u6216\u8005\u4e3b\u952e\u626b\u63cf\uff1b
    4.ref<\/code>\uff1a\u975e\u552f\u4e00\u6027\u7d22\u5f15\u626b\u63cf\uff0c\u8fd4\u56de\u5339\u914d\u67d0\u4e2a\u5355\u72ec\u503c\u7684\u6240\u6709\u884c\uff0c\u672c\u8d28\u4e0a\u4e5f\u662f\u4e00\u79cd\u7d22\u5f15\u8bbf\u95ee\uff0c\u5b83\u8fd4\u56de\u6240\u6709\u5339\u914d\u67d0\u4e2a\u5355\u72ec\u503c\u7684\u884c\uff0c\u53ef\u80fd\u4f1a\u627e\u591a\u4e2a\u7b26\u5408\u6761\u4ef6\u7684\u884c\uff0c\u5c5e\u4e8e\u67e5\u627e\u548c\u626b\u63cf\u7684\u6df7\u5408\u4f53\uff1b
    5.range<\/code>\uff1a\u53ea\u68c0\u7d22\u7ed9\u5b9a\u8303\u56f4\u7684\u884c\uff0c\u4f7f\u7528\u4e00\u4e2a\u7d22\u5f15\u6765\u9009\u62e9\u884c\u3002key \u5217\u663e\u793a\u4f7f\u7528\u4e86\u54ea\u4e2a\u7d22\u5f15\uff0c\u4e00\u822c\u5c31\u662f where \u8bed\u53e5\u4e2d\u51fa\u73b0\u4e86 between\u3001in \u7b49\u8303\u56f4\u7684\u67e5\u8be2\u3002\u8fd9\u79cd\u8303\u56f4\u626b\u63cf\u7d22\u5f15\u626b\u63cf\u6bd4\u5168\u8868\u626b\u63cf\u8981\u597d\uff0c\u56e0\u4e3a\u5b83\u5f00\u59cb\u4e8e\u7d22\u5f15\u7684\u67d0\u4e00\u4e2a\u70b9\uff0c\u800c\u7ed3\u675f\u53e6\u4e00\u4e2a\u70b9\uff0c\u4e0d\u7528\u5168\u8868\u626b\u63cf\uff1b
    6.index<\/code>\uff1aindex \u4e0e all \u533a\u522b\u4e3a index \u7c7b\u578b\u53ea\u904d\u5386\u7d22\u5f15\u6811\u3002\u901a\u5e38\u6bd4 all \u5feb\uff0c\u56e0\u4e3a\u7d22\u5f15\u6587\u4ef6\u6bd4\u6570\u636e\u6587\u4ef6\u5c0f\u5f88\u591a\uff1b
    7.all<\/code>\uff1a\u904d\u5386\u5168\u8868\u4ee5\u627e\u5230\u5339\u914d\u7684\u884c\uff1b
    \u6ce8\u610f<\/code>\uff1a\u4e00\u822c\u4fdd\u8bc1\u67e5\u8be2\u81f3\u5c11\u8fbe\u5230 range \u7ea7\u522b\uff0c\u6700\u597d\u80fd\u8fbe\u5230 ref\u3002<\/td>\n<\/tr>\n
    possible_keys<\/td>\n\u6307\u51fa MySQL \u80fd\u4f7f\u7528\u54ea\u4e2a\u7d22\u5f15\u5728\u8be5\u8868\u4e2d\u627e\u5230\u884c\u3002<\/td>\n<\/tr>\n
    key<\/td>\n\u663e\u793a MySQL \u5b9e\u9645\u51b3\u5b9a\u4f7f\u7528\u7684\u952e(\u7d22\u5f15)\u3002\u5982\u679c\u6ca1\u6709\u9009\u62e9\u7d22\u5f15\uff0c\u952e\u662f NULL\u3002\u67e5\u8be2\u4e2d\u5982\u679c\u4f7f\u7528\u8986\u76d6\u7d22\u5f15\uff0c\u5219\u8be5\u7d22\u5f15\u548c\u67e5\u8be2\u7684 select \u5b57\u6bb5\u91cd\u53e0\u3002<\/td>\n<\/tr>\n
    key_len<\/td>\n\u8868\u793a\u7d22\u5f15\u4e2d\u4f7f\u7528\u7684\u5b57\u8282\u6570\uff0c\u8be5\u5217\u8ba1\u7b97\u67e5\u8be2\u4e2d\u4f7f\u7528\u7684\u7d22\u5f15\u7684\u957f\u5ea6\u5728\u4e0d\u635f\u5931\u7cbe\u5ea6\u7684\u60c5\u51b5\u4e0b\uff0c\u957f\u5ea6\u8d8a\u77ed\u8d8a\u597d\u3002\u5982\u679c\u952e\u662f NULL\uff0c\u5219\u957f\u5ea6\u4e3a NULL\u3002\u8be5\u5b57\u6bb5\u663e\u793a\u4e3a\u7d22\u5f15\u5b57\u6bb5\u7684\u6700\u5927\u53ef\u80fd\u957f\u5ea6\uff0c\u5e76\u975e\u5b9e\u9645\u4f7f\u7528\u957f\u5ea6\u3002<\/td>\n<\/tr>\n
    ref<\/td>\n\u663e\u793a\u7d22\u5f15\u7684\u54ea\u4e00\u5217\u88ab\u4f7f\u7528\u4e86\uff0c\u5982\u679c\u6709\u53ef\u80fd\u662f\u4e00\u4e2a\u5e38\u6570\uff0c\u54ea\u4e9b\u5217\u6216\u5e38\u91cf\u88ab\u7528\u4e8e\u67e5\u8be2\u7d22\u5f15\u5217\u4e0a\u7684\u503c\u3002<\/td>\n<\/tr>\n
    rows<\/td>\n\u6839\u636e\u8868\u7edf\u8ba1\u4fe1\u606f\u4ee5\u53ca\u7d22\u5f15\u9009\u7528\u60c5\u51b5\uff0c\u5927\u81f4\u4f30\u7b97\u51fa\u627e\u5230\u6240\u9700\u7684\u8bb0\u5f55\u6240\u9700\u8981\u8bfb\u53d6\u7684\u884c\u6570\u3002<\/td>\n<\/tr>\n
    extra<\/td>\n\u5305\u542b\u4e0d\u9002\u5408\u5728\u5176\u4ed6\u5217\u4e2d\u663e\u793a\uff0c\u4f46\u662f\u5341\u5206\u91cd\u8981\u7684\u989d\u5916\u4fe1\u606f
    1.Using filesort<\/code>\uff1a\u8bf4\u660e mysql \u4f1a\u5bf9\u6570\u636e\u9002\u7528\u4e00\u4e2a\u5916\u90e8\u7684\u7d22\u5f15\u6392\u5e8f\u3002\u800c\u4e0d\u662f\u6309\u7167\u8868\u5185\u7684\u7d22\u5f15\u987a\u5e8f\u8fdb\u884c\u8bfb\u53d6\u3002MySQL \u4e2d\u65e0\u6cd5\u5229\u7528\u7d22\u5f15\u5b8c\u6210\u6392\u5e8f\u64cd\u4f5c\u79f0\u4e3a\u201c\u6587\u4ef6\u6392\u5e8f\u201d\uff1b
    2.Using temporary<\/code>\uff1a\u4f7f\u7528\u4e86\u4e34\u65f6\u8868\u4fdd\u5b58\u4e2d\u95f4\u7ed3\u679c\uff0cmysql \u5728\u67e5\u8be2\u7ed3\u679c\u6392\u5e8f\u65f6\u4f7f\u7528\u4e34\u65f6\u8868\u3002\u5e38\u89c1\u4e8e\u6392\u5e8f order by \u548c\u5206\u7ec4\u67e5\u8be2 group by\uff1b
    3.Using index<\/code>\uff1a\u8868\u793a\u76f8\u5e94\u7684 select \u64cd\u4f5c\u7528\u4f7f\u7528\u8986\u76d6\u7d22\u5f15\uff0c\u907f\u514d\u8bbf\u95ee\u4e86\u8868\u7684\u6570\u636e\u884c\u3002\u5982\u679c\u540c\u65f6\u51fa\u73b0 using where\uff0c\u8868\u540d\u7d22\u5f15\u88ab\u7528\u6765\u6267\u884c\u7d22\u5f15\u952e\u503c\u7684\u67e5\u627e\uff1b\u5982\u679c\u6ca1\u6709\u540c\u65f6\u51fa\u73b0 using where\uff0c\u8868\u540d\u7d22\u5f15\u7528\u6765\u8bfb\u53d6\u6570\u636e\u800c\u975e\u6267\u884c\u67e5\u8be2\u52a8\u4f5c\uff1b
    4.Using where<\/code>\uff1a\u8868\u660e\u4f7f\u7528 where \u8fc7\u6ee4\uff1b
    5.using join buffer<\/code>\uff1a\u4f7f\u7528\u4e86\u8fde\u63a5\u7f13\u5b58\uff1b
    6.impossible where<\/code>\uff1awhere \u5b50\u53e5\u7684\u503c\u603b\u662f false\uff0c\u4e0d\u80fd\u7528\u6765\u83b7\u53d6\u4efb\u4f55\u5143\u7ec4\uff1b
    7.select tables optimized away<\/code>\uff1a\u5728\u6ca1\u6709 group by \u5b50\u53e5\u7684\u60c5\u51b5\u4e0b\uff0c\u57fa\u4e8e\u7d22\u5f15\u4f18\u5316 min\u3001max \u64cd\u4f5c\u6216\u8005\u5bf9\u4e8e MyISAM \u5b58\u50a8\u5f15\u64ce\u4f18\u5316 count\uff08*\uff09\uff0c\u4e0d\u5fc5\u7b49\u5230\u6267\u884c\u9636\u6bb5\u518d\u8fdb\u884c\u8ba1\u7b97\uff0c\u67e5\u8be2\u6267\u884c\u8ba1\u5212\u751f\u6210\u7684\u9636\u6bb5\u5373\u5b8c\u6210\u4f18\u5316\uff1b
    8.distinct<\/code>\uff1a\u4f18\u5316 distinct \u64cd\u4f5c\uff0c\u5728\u627e\u5230\u7b2c\u4e00\u5339\u914d\u7684\u5143\u7ec4\u540e\u5373\u505c\u6b62\u627e\u540c\u6837\u503c\u7684\u52a8\u4f5c\u3002<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/section>\n
    extended \u5173\u952e\u5b57<\/span><\/h2>\n
    extended \u5173\u952e\u5b57\u4ec5\u5bf9 select \u8bed\u53e5\u6709\u6548\uff0c\u5728 Explain \u540e\u4f7f\u7528 extended \u5173\u952e\u5b57\uff0c\u53ef\u4ee5\u663e\u793a filtered \u5217\u663e\u793a\u4e86\u901a\u8fc7\u6761\u4ef6\u8fc7\u6ee4\u51fa\u7684\u884c\u6570\u7684\u767e\u5206\u6bd4\u4f30\u8ba1\u503c\u3002<\/p>\n
    filtered<\/code>\u00a0\u5217\u7ed9\u51fa\u4e86\u4e00\u4e2a\u767e\u5206\u6bd4\u7684\u503c\uff0c\u8fd9\u4e2a\u767e\u5206\u6bd4\u503c\u548c rows \u5217\u7684\u503c\u4e00\u8d77\u4f7f\u7528\uff0c\u53ef\u4ee5\u4f30\u8ba1\u51fa\u90a3\u4e9b\u5c06\u8981\u548c explain \u4e2d\u7684\u524d\u4e00\u4e2a\u8868\u8fdb\u884c\u8fde\u63a5\u7684\u884c\u7684\u6570\u76ee\uff0c\u524d\u4e00\u4e2a\u8868\u5c31\u662f\u6307 explain \u7684 id \u5217\u7684\u503c\u6bd4\u5f53\u524d\u8868\u7684 id \u5c0f\u7684\u8868\u3002<\/p>\n
    SQL \u6267\u884c\u987a\u5e8f<\/span><\/h2>\n
    (9)\u00a0select<\/span>\u00a0
    (10<\/span>)\u00a0distinct<\/span>\u00a0column<\/span>,
    (6<\/span>)\u00a0AGG_FUNC(column<\/span>\u00a0or<\/span>\u00a0expression),\u00a0...
    (1<\/span>)\u00a0from<\/span>\u00a0left_table
    (3<\/span>)\u00a0join<\/span>\u00a0right_table
    (2<\/span>)\u00a0on<\/span>\u00a0tablename.column\u00a0=\u00a0other_tablename.column
    (4<\/span>)\u00a0where<\/span>\u00a0constraint_expression
    (5<\/span>)\u00a0group<\/span>\u00a0by<\/span>\u00a0column<\/span>
    (7<\/span>)\u00a0with<\/span>\u00a0cube<\/span>|rollup<\/span>
    (8<\/span>)\u00a0having<\/span>\u00a0constraint_expression
    (11<\/span>)\u00a0order<\/span>\u00a0by<\/span>\u00a0column<\/span>\u00a0asc<\/span>|desc<\/span>
    (12<\/span>)\u00a0limit<\/span>\u00a0count<\/span>\u00a0offset<\/span>\u00a0count<\/span>;
    <\/code><\/pre>\n
    \u5b9e\u9645\u4e0a SQL \u6267\u884c\u987a\u5e8f\uff1a<\/p>\n
      \n
    • \n
      \u5148\u6267\u884c from\uff0cjoin \u6765\u786e\u5b9a\u8868\u4e4b\u95f4\u7684\u8fde\u63a5\u5173\u7cfb\uff0c\u5f97\u5230\u521d\u6b65\u7684\u6570\u636e\uff1b<\/section>\n<\/li>\n
    • \n
      where \u5bf9\u6570\u636e\u8fdb\u884c\u666e\u901a\u7684\u521d\u6b65\u7684\u7b5b\u9009\uff1b<\/section>\n<\/li>\n
    • \n
      group by \u5206\u7ec4\uff1b<\/section>\n<\/li>\n
    • \n
      \u5404\u7ec4\u5206\u522b\u6267\u884c having \u4e2d\u7684\u666e\u901a\u7b5b\u9009\u6216\u8005\u805a\u5408\u51fd\u6570\u7b5b\u9009\uff1b<\/section>\n<\/li>\n
    • \n
      \u7136\u540e\u518d\u6839\u636e\u6211\u4eec\u8981\u7684\u6570\u636e\u8fdb\u884c select\uff0c\u53ef\u4ee5\u662f\u666e\u901a\u5b57\u6bb5\u67e5\u8be2\u4e5f\u53ef\u4ee5\u662f\u83b7\u53d6\u805a\u5408\u51fd\u6570\u7684\u67e5\u8be2\u7ed3\u679c\uff0c\u5982\u679c\u662f\u96c6\u5408\u51fd\u6570\uff0cselect \u7684\u67e5\u8be2\u7ed3\u679c\u4f1a\u65b0\u589e\u4e00\u6761\u5b57\u6bb5\uff1b<\/section>\n<\/li>\n
    • \n
      \u5c06\u67e5\u8be2\u7ed3\u679c\u53bb\u91cd distinct\uff1b<\/section>\n<\/li>\n
    • \n
      \u6700\u540e\u5408\u5e76\u5404\u7ec4\u7684\u67e5\u8be2\u7ed3\u679c\uff0c\u6309\u7167 order by \u7684\u6761\u4ef6\u8fdb\u884c\u6392\u5e8f\u3002<\/section>\n<\/li>\n<\/ul>\n
      \u5173\u952e\u5b57\u7684\u987a\u5e8f\u662f\u4e0d\u80fd\u98a0\u5012\u7684\uff1a<\/p>\n
      SELECT<\/span>\u00a0...\u00a0FROM<\/span>\u00a0...\u00a0WHERE<\/span>\u00a0...\u00a0GROUP<\/span>\u00a0BY<\/span>\u00a0...\u00a0HAVING<\/span>\u00a0...\u00a0ORDER<\/span>\u00a0BY<\/span>\u00a0...
      <\/code><\/pre>\n
      SELECT \u8bed\u53e5\u7684\u6267\u884c\u987a\u5e8f\uff08\u5728 MySQL \u548c Oracle \u4e2d\uff0cSELECT \u6267\u884c\u987a\u5e8f\u57fa\u672c\u76f8\u540c\uff09\uff1a<\/p>\n
      FROM\u00a0>\u00a0WHERE\u00a0>\u00a0GROUP\u00a0BY\u00a0>\u00a0HAVING\u00a0>\u00a0SELECT<\/span>\u7684\u5b57\u6bb5\u00a0>\u00a0DISTINCT<\/span>\u00a0>\u00a0ORDER<\/span>\u00a0BY<\/span>\u00a0>\u00a0LIMIT<\/span>
      <\/code><\/pre>\n
      \u4f18\u5316\u5b9e\u8df5\u6ce8\u610f\u70b9<\/span><\/h2>\n
      1\u3001\u5bf9\u67e5\u8be2\u8fdb\u884c\u4f18\u5316\uff0c\u8981\u5c3d\u91cf\u907f\u514d\u5168\u8868\u626b\u63cf\uff0c\u9996\u5148\u5e94\u8003\u8651\u5728 where \u53ca order by \u6d89\u53ca\u7684\u5217\u4e0a\u5efa\u7acb\u7d22\u5f15\u3002<\/p>\n
      2\u3001\u5e94\u5c3d\u91cf\u907f\u514d\u5728 where \u5b50\u53e5\u4e2d\u5bf9\u5b57\u6bb5\u8fdb\u884c null \u503c\u5224\u65ad\uff0c\u5426\u5219\u5c06\u5bfc\u81f4\u5f15\u64ce\u653e\u5f03\u4f7f\u7528\u7d22\u5f15\u800c\u8fdb\u884c\u5168\u8868\u626b\u63cf\uff0c\u5982\uff1a<\/p>\n
      select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0num<\/span>\u00a0is<\/span>\u00a0null<\/span>;
      <\/code><\/pre>\n
        \n
      • \n
        \u6700\u597d\u4e0d\u8981\u7ed9\u6570\u636e\u5e93\u7559 NULL\uff0c\u5c3d\u53ef\u80fd\u7684\u4f7f\u7528 NOT NULL \u586b\u5145\u6570\u636e\u5e93;<\/section>\n<\/li>\n
      • \n
        \u5907\u6ce8\u3001\u63cf\u8ff0\u3001\u8bc4\u8bba\u4e4b\u7c7b\u7684\u53ef\u4ee5\u8bbe\u7f6e\u4e3a NULL\uff0c\u5176\u4ed6\u7684\uff0c\u6700\u597d\u4e0d\u8981\u4f7f\u7528 NULL;<\/section>\n<\/li>\n
      • \n
        \u4e0d\u8981\u4ee5\u4e3a NULL \u4e0d\u9700\u8981\u7a7a\u95f4\uff0c\u6bd4\u5982\uff1achar(100) \u578b\uff0c\u5728\u5b57\u6bb5\u5efa\u7acb\u65f6\uff0c\u7a7a\u95f4\u5c31\u56fa\u5b9a\u4e86\uff0c \u4e0d\u7ba1\u662f\u5426\u63d2\u5165\u503c\uff08NULL \u4e5f\u5305\u542b\u5728\u5185\uff09\uff0c\u90fd\u662f\u5360\u7528 100 \u4e2a\u5b57\u7b26\u7684\u7a7a\u95f4\u7684\uff0c\u5982\u679c\u662f varchar \u8fd9\u6837\u7684\u53d8\u957f\u5b57\u6bb5\uff0cnull \u4e0d\u5360\u7528\u7a7a\u95f4\uff1b<\/section>\n<\/li>\n
      • \n
        \u53ef\u4ee5\u5728 num \u4e0a\u8bbe\u7f6e\u9ed8\u8ba4\u503c 0\uff0c\u786e\u4fdd\u8868\u4e2d num \u5217\u6ca1\u6709 null \u503c\u3002<\/section>\n<\/li>\n<\/ul>\n
        3\u3001\u5e94\u5c3d\u91cf\u907f\u514d\u5728 where \u5b50\u53e5\u4e2d\u4f7f\u7528 != \u6216 <> \u64cd\u4f5c\u7b26\uff0c\u5426\u5219\u5c06\u5f15\u64ce\u653e\u5f03\u4f7f\u7528\u7d22\u5f15\u800c\u8fdb\u884c\u5168\u8868\u626b\u63cf\u30024.\u5e94\u5c3d\u91cf\u907f\u514d\u5728 where \u5b50\u53e5\u4e2d\u4f7f\u7528 or \u6765\u8fde\u63a5\u6761\u4ef6\uff0c\u5982\u679c\u4e00\u4e2a\u5b57\u6bb5\u6709\u7d22\u5f15\uff0c\u4e00\u4e2a\u5b57\u6bb5\u6ca1\u6709\u7d22\u5f15\uff0c\u5c06\u5bfc\u81f4\u5f15\u64ce\u653e\u5f03\u4f7f\u7528\u7d22\u5f15\u800c\u8fdb\u884c\u5168\u8868\u626b\u63cf\uff0c\u5982\uff1a<\/p>\n
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0num<\/span>=10<\/span>\u00a0or<\/span>\u00a0Name<\/span>\u00a0=\u00a0'admin'<\/span>;
        <\/code><\/pre>\n
        \u53ef\u4ee5\u8fd9\u6837\u67e5\u8be2\uff1aselect<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0num<\/span>\u00a0=\u00a010<\/span>
        union<\/span>\u00a0all<\/span>
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0Name<\/span>\u00a0=\u00a0'admin'<\/span>
        <\/code><\/pre>\n
        5\u3001in \u548c not in \u4e5f\u8981\u614e\u7528\uff0c\u5426\u5219\u4f1a\u5bfc\u81f4\u5168\u8868\u626b\u63cf\uff0c\u5982\uff1a<\/p>\n
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0num<\/span>\u00a0in<\/span>(1<\/span>,2<\/span>,3<\/span>);
        <\/code><\/pre>\n
        \u5bf9\u4e8e\u8fde\u7eed\u7684\u6570\u503c\uff0c\u80fd\u7528 between \u5c31\u4e0d\u8981\u7528 in \u4e86\uff1a<\/p>\n
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0num<\/span>\u00a0between<\/span>\u00a01<\/span>\u00a0and<\/span>\u00a03<\/span>;
        <\/code><\/pre>\n
        \u5f88\u591a\u65f6\u5019\u7528 exists \u4ee3\u66ff in \u662f\u4e00\u4e2a\u597d\u7684\u9009\u62e9\uff1a<\/p>\n
        select<\/span>\u00a0num<\/span>\u00a0from<\/span>\u00a0a\u00a0where<\/span>\u00a0num<\/span>\u00a0in<\/span>(select<\/span>\u00a0num<\/span>\u00a0from<\/span>\u00a0b);
        <\/code><\/pre>\n
        \u7528\u4e0b\u9762\u7684\u8bed\u53e5\u66ff\u6362\uff1a<\/p>\n
        select<\/span>\u00a0num<\/span>\u00a0from<\/span>\u00a0a\u00a0where<\/span>\u00a0exists<\/span>(select<\/span>\u00a01<\/span>\u00a0from<\/span>\u00a0b\u00a0where<\/span>\u00a0num<\/span>=a.num);
        <\/code><\/pre>\n
        6\u3001\u4e0b\u9762\u7684\u67e5\u8be2\u4e5f\u5c06\u5bfc\u81f4\u5168\u8868\u626b\u63cf\uff1a<\/p>\n
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0name<\/span>\u00a0like<\/span>\u00a0'%abc%'<\/span>;
        <\/code><\/pre>\n
        \n
        \u82e5\u8981\u63d0\u9ad8\u6548\u7387\uff0c\u53ef\u4ee5\u8003\u8651\u5168\u6587\u68c0\u7d22\u3002<\/p>\n<\/blockquote>\n
        7\u3001\u5982\u679c\u5728 where \u5b50\u53e5\u4e2d\u4f7f\u7528\u53c2\u6570\uff0c\u4e5f\u4f1a\u5bfc\u81f4\u5168\u8868\u626b\u63cf\u3002\u56e0\u4e3aSQL\u53ea\u6709\u5728\u8fd0\u884c\u65f6\u624d\u4f1a\u89e3\u6790\u5c40\u90e8\u53d8\u91cf\uff0c\u4f46\u4f18\u5316\u7a0b\u5e8f\u4e0d\u80fd\u5c06\u8bbf\u95ee\u8ba1\u5212\u7684\u9009\u62e9\u63a8\u8fdf\u5230\u8fd0\u884c\u65f6\uff1b\u5b83\u5fc5\u987b\u5728\u7f16\u8bd1\u65f6\u8fdb\u884c\u9009\u62e9\u3002\u7136 \u800c\uff0c\u5982\u679c\u5728\u7f16\u8bd1\u65f6\u5efa\u7acb\u8bbf\u95ee\u8ba1\u5212\uff0c\u53d8\u91cf\u7684\u503c\u8fd8\u662f\u672a\u77e5\u7684\uff0c\u56e0\u800c\u65e0\u6cd5\u4f5c\u4e3a\u7d22\u5f15\u9009\u62e9\u7684\u8f93\u5165\u9879\u3002\u5982\u4e0b\u9762\u8bed\u53e5\u5c06\u8fdb\u884c\u5168\u8868\u626b\u63cf\uff1a<\/p>\n
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0num<\/span>\u00a0=\u00a0@num<\/span>;
        <\/code><\/pre>\n
        \u53ef\u4ee5\u6539\u4e3a\u5f3a\u5236\u67e5\u8be2\u4f7f\u7528\u7d22\u5f15\uff1a<\/p>\n
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0with<\/span>(index<\/span>(\u7d22\u5f15\u540d))\u00a0where<\/span>\u00a0num<\/span>\u00a0=\u00a0@num<\/span>;
        <\/code><\/pre>\n
        \u5e94\u5c3d\u91cf\u907f\u514d\u5728 where \u5b50\u53e5\u4e2d\u5bf9\u5b57\u6bb5\u8fdb\u884c\u8868\u8fbe\u5f0f\u64cd\u4f5c\uff0c\u8fd9\u5c06\u5bfc\u81f4\u5f15\u64ce\u653e\u5f03\u4f7f\u7528\u7d22\u5f15\u800c\u8fdb\u884c\u5168\u8868\u626b\u63cf\u3002\u5982\uff1a<\/p>\n
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0num<\/span>\/2<\/span>\u00a0=\u00a0100<\/span>;
        <\/code><\/pre>\n
        \u5e94\u6539\u4e3a:<\/p>\n
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0num<\/span>\u00a0=\u00a0100<\/span>*2<\/span>;
        <\/code><\/pre>\n
        9\u3001\u5e94\u5c3d\u91cf\u907f\u514d\u5728where\u5b50\u53e5\u4e2d\u5bf9\u5b57\u6bb5\u8fdb\u884c\u51fd\u6570\u64cd\u4f5c\uff0c\u8fd9\u5c06\u5bfc\u81f4\u5f15\u64ce\u653e\u5f03\u4f7f\u7528\u7d22\u5f15\u800c\u8fdb\u884c\u5168\u8868\u626b\u63cf\u3002\u5982\uff1a<\/p>\n
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0substring<\/span>(name<\/span>,1<\/span>,3<\/span>)\u00a0=\u00a0'abc'<\/span>;\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0-\u2013\u00a0name\u00a0\u4ee5abc\u00a0\u5f00\u5934\u7684\u00a0id
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0datediff<\/span>(day<\/span>,createdate,'2005-11-30'<\/span>)\u00a0=\u00a00<\/span>;\u00a0\u00a0\u00a0-\u2013\u00a0'2005-11-30'\u00a0\u751f\u6210\u7684id
        <\/code><\/pre>\n
        \u5e94\u6539\u4e3a:<\/p>\n
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0name<\/span>\u00a0like<\/span>\u00a0'abc%'<\/span>;
        select<\/span>\u00a0id<\/span>\u00a0from<\/span>\u00a0t\u00a0where<\/span>\u00a0createdate\u00a0>=\u00a0'2005-11-30'<\/span>\u00a0and<\/span>\u00a0createdate\u00a0<\u00a0'2005-12-1'<\/span>;
        <\/code><\/pre>\n
        10\u3001\u4e0d\u8981\u5728 where \u5b50\u53e5\u4e2d\u7684\u201c=\u201d\u5de6\u8fb9\u8fdb\u884c\u51fd\u6570\u3001\u7b97\u672f\u8fd0\u7b97\u6216\u5176\u4ed6\u8868\u8fbe\u5f0f\u8fd0\u7b97\uff0c\u5426\u5219\u7cfb\u7edf\u5c06\u53ef\u80fd\u65e0\u6cd5\u6b63\u786e\u4f7f\u7528\u7d22\u5f15\u3002<\/p>\n
        11\u3001\u5728\u4f7f\u7528\u7d22\u5f15\u5b57\u6bb5\u4f5c\u4e3a\u6761\u4ef6\u65f6\uff0c\u5982\u679c\u8be5\u7d22\u5f15\u662f\u590d\u5408\u7d22\u5f15\uff0c\u90a3\u4e48\u5fc5\u987b\u4f7f\u7528\u5230\u8be5\u7d22\u5f15\u4e2d\u7684\u7b2c\u4e00\u4e2a\u5b57\u6bb5\u4f5c\u4e3a\u6761\u4ef6\u65f6\u624d\u80fd\u4fdd\u8bc1\u7cfb\u7edf\u4f7f\u7528\u8be5\u7d22\u5f15\uff0c\u5426\u5219\u8be5\u7d22\u5f15\u5c06\u4e0d\u4f1a\u88ab\u4f7f\u7528\uff0c\u5e76\u4e14\u5e94\u5c3d\u53ef\u80fd\u7684\u8ba9\u5b57\u6bb5\u987a\u5e8f\u4e0e\u7d22\u5f15\u987a\u5e8f\u76f8\u4e00\u81f4\u3002<\/p>\n
        12\u3001\u4e0d\u8981\u5199\u4e00\u4e9b\u6ca1\u6709\u610f\u4e49\u7684\u67e5\u8be2\uff0c\u5982\u9700\u8981\u751f\u6210\u4e00\u4e2a\u7a7a\u8868\u7ed3\u6784\uff1a<\/p>\n
        select<\/span>\u00a0col1,col2\u00a0into<\/span>\u00a0#t\u00a0from\u00a0t\u00a0where\u00a01=0;<\/span>
        <\/code><\/pre>\n
        \u8fd9\u7c7b\u4ee3\u7801\u4e0d\u4f1a\u8fd4\u56de\u4efb\u4f55\u7ed3\u679c\u96c6\uff0c\u4f46\u662f\u4f1a\u6d88\u8017\u7cfb\u7edf\u8d44\u6e90\u7684\uff0c\u5e94\u6539\u6210\u8fd9\u6837\uff1a<\/p>\n
        create<\/span>\u00a0table<\/span>\u00a0#t(\u2026);<\/span>
        <\/code><\/pre>\n
        13\u3001Update \u8bed\u53e5\uff0c\u5982\u679c\u53ea\u66f4\u6539 1\u30012 \u4e2a\u5b57\u6bb5\uff0c\u4e0d\u8981 Update \u5168\u90e8\u5b57\u6bb5\uff0c\u5426\u5219\u9891\u7e41\u8c03\u7528\u4f1a\u5f15\u8d77\u660e\u663e\u7684\u6027\u80fd\u6d88\u8017\uff0c\u540c\u65f6\u5e26\u6765\u5927\u91cf\u65e5\u5fd7\u3002<\/p>\n
        14\u3001\u5bf9\u4e8e\u591a\u5f20\u5927\u6570\u636e\u91cf\uff08\u8fd9\u91cc\u51e0\u767e\u6761\u5c31\u7b97\u5927\u4e86\uff09\u7684\u8868 JOIN\uff0c\u8981\u5148\u5206\u9875\u518d JOIN\uff0c\u5426\u5219\u903b\u8f91\u8bfb\u4f1a\u5f88\u9ad8\uff0c\u6027\u80fd\u5f88\u5dee\u3002<\/p>\n
        15\u3001select count(*) from table<\/code>\u00a0\u8fd9\u6837\u4e0d\u5e26\u4efb\u4f55\u6761\u4ef6\u7684 count \u4f1a\u5f15\u8d77\u5168\u8868\u626b\u63cf\uff0c\u5e76\u4e14\u6ca1\u6709\u4efb\u4f55\u4e1a\u52a1\u610f\u4e49\uff0c\u662f\u4e00\u5b9a\u8981\u675c\u7edd\u7684\u3002<\/p>\n
        16\u3001\u7d22\u5f15\u5e76\u4e0d\u662f\u8d8a\u591a\u8d8a\u597d\uff0c\u7d22\u5f15\u56fa\u7136\u53ef\u4ee5\u63d0\u9ad8\u76f8\u5e94\u7684 select \u7684\u6548\u7387\uff0c\u4f46\u540c\u65f6\u4e5f\u964d\u4f4e\u4e86 insert \u53ca update \u7684\u6548\u7387\uff0c\u56e0\u4e3a insert \u6216 update \u65f6\u6709\u53ef\u80fd\u4f1a\u91cd\u5efa\u7d22\u5f15\uff0c\u6240\u4ee5\u600e\u6837\u5efa\u7d22\u5f15\u9700\u8981\u614e\u91cd\u8003\u8651\uff0c\u89c6\u5177\u4f53\u60c5\u51b5\u800c\u5b9a\u3002\u4e00\u4e2a\u8868\u7684\u7d22\u5f15\u6570\u6700\u597d\u4e0d\u8981\u8d85\u8fc7 6 \u4e2a\uff0c\u82e5\u592a\u591a\u5219\u5e94\u8003\u8651\u4e00\u4e9b\u4e0d\u5e38\u4f7f\u7528\u5230\u7684\u5217\u4e0a\u5efa\u7684\u7d22\u5f15\u662f\u5426\u6709 \u5fc5\u8981\u3002<\/p>\n
        17\u3001\u5e94\u5c3d\u53ef\u80fd\u7684\u907f\u514d\u66f4\u65b0 clustered \u7d22\u5f15\u6570\u636e\u5217\uff0c\u56e0\u4e3a clustered \u7d22\u5f15\u6570\u636e\u5217\u7684\u987a\u5e8f\u5c31\u662f\u8868\u8bb0\u5f55\u7684\u7269\u7406\u5b58\u50a8\u987a\u5e8f\uff0c\u4e00\u65e6\u8be5\u5217\u503c\u6539\u53d8\u5c06\u5bfc\u81f4\u6574\u4e2a\u8868\u8bb0\u5f55\u7684\u987a\u5e8f\u7684\u8c03\u6574\uff0c\u4f1a\u8017\u8d39\u76f8\u5f53\u5927\u7684\u8d44\u6e90\u3002\u82e5\u5e94\u7528\u7cfb\u7edf\u9700\u8981\u9891\u7e41\u66f4\u65b0 clustered \u7d22\u5f15\u6570\u636e\u5217\uff0c\u90a3\u4e48\u9700\u8981\u8003\u8651\u662f\u5426\u5e94\u5c06\u8be5\u7d22\u5f15\u5efa\u4e3a clustered \u7d22\u5f15\u3002<\/p>\n
        18\u3001\u5c3d\u91cf\u4f7f\u7528\u6570\u5b57\u578b\u5b57\u6bb5\uff0c\u82e5\u53ea\u542b\u6570\u503c\u4fe1\u606f\u7684\u5b57\u6bb5\u5c3d\u91cf\u4e0d\u8981\u8bbe\u8ba1\u4e3a\u5b57\u7b26\u578b\uff0c\u8fd9\u4f1a\u964d\u4f4e\u67e5\u8be2\u548c\u8fde\u63a5\u7684\u6027\u80fd\uff0c\u5e76\u4f1a\u589e\u52a0\u5b58\u50a8\u5f00\u9500\u3002\u8fd9\u662f\u56e0\u4e3a\u5f15\u64ce\u5728\u5904\u7406\u67e5\u8be2\u548c\u8fde \u63a5\u65f6\u4f1a\u9010\u4e2a\u6bd4\u8f83\u5b57\u7b26\u4e32\u4e2d\u6bcf\u4e00\u4e2a\u5b57\u7b26\uff0c\u800c\u5bf9\u4e8e\u6570\u5b57\u578b\u800c\u8a00\u53ea\u9700\u8981\u6bd4\u8f83\u4e00\u6b21\u5c31\u591f\u4e86\u3002<\/p>\n
        19\u3001\u5c3d\u53ef\u80fd\u7684\u4f7f\u7528\u00a0varchar\/nvarchar<\/code>\u00a0\u4ee3\u66ff\u00a0char\/nchar<\/code>\uff0c\u56e0\u4e3a\u9996\u5148\u53d8\u957f\u5b57\u6bb5\u5b58\u50a8\u7a7a\u95f4\u5c0f\uff0c\u53ef\u4ee5\u8282\u7701\u5b58\u50a8\u7a7a\u95f4\uff0c\u5176\u6b21\u5bf9\u4e8e\u67e5\u8be2\u6765\u8bf4\uff0c\u5728\u4e00\u4e2a\u76f8\u5bf9\u8f83\u5c0f\u7684\u5b57\u6bb5\u5185\u641c\u7d22\u6548\u7387\u663e\u7136\u8981\u9ad8\u4e9b\u3002<\/p>\n
        20\u3001\u4efb\u4f55\u5730\u65b9\u90fd\u4e0d\u8981\u4f7f\u7528\u00a0select * from t<\/code>\u00a0\uff0c\u7528\u5177\u4f53\u7684\u5b57\u6bb5\u5217\u8868\u4ee3\u66ff \u201c*\u201d \uff0c\u4e0d\u8981\u8fd4\u56de\u7528\u4e0d\u5230\u7684\u4efb\u4f55\u5b57\u6bb5\u3002<\/p>\n
        21\u3001\u5c3d\u91cf\u4f7f\u7528\u8868\u53d8\u91cf\u6765\u4ee3\u66ff\u4e34\u65f6\u8868\u3002\u5982\u679c\u8868\u53d8\u91cf\u5305\u542b\u5927\u91cf\u6570\u636e\uff0c\u8bf7\u6ce8\u610f\u7d22\u5f15\u975e\u5e38\u6709\u9650\uff08\u53ea\u6709\u4e3b\u952e\u7d22\u5f15\uff09\u3002<\/p>\n
        22\u3001\u907f\u514d\u9891\u7e41\u521b\u5efa\u548c\u5220\u9664\u4e34\u65f6\u8868\uff0c\u4ee5\u51cf\u5c11\u7cfb\u7edf\u8868\u8d44\u6e90\u7684\u6d88\u8017\u3002\u4e34\u65f6\u8868\u5e76\u4e0d\u662f\u4e0d\u53ef\u4f7f\u7528\uff0c\u9002\u5f53\u5730\u4f7f\u7528\u5b83\u4eec\u53ef\u4ee5\u4f7f\u67d0\u4e9b\u4f8b\u7a0b\u66f4\u6709\u6548\uff0c\u4f8b\u5982\uff0c\u5f53\u9700\u8981\u91cd\u590d\u5f15\u7528\u5927\u578b\u8868\u6216\u5e38\u7528\u8868\u4e2d\u7684\u67d0\u4e2a\u6570\u636e\u96c6\u65f6\u3002\u4f46\u662f\uff0c\u5bf9\u4e8e\u4e00\u6b21\u6027\u4e8b\u4ef6\uff0c \u6700\u597d\u4f7f\u7528\u5bfc\u51fa\u8868\u3002<\/p>\n
        23\u3001\u5728\u65b0\u5efa\u4e34\u65f6\u8868\u65f6\uff0c\u5982\u679c\u4e00\u6b21\u6027\u63d2\u5165\u6570\u636e\u91cf\u5f88\u5927\uff0c\u90a3\u4e48\u53ef\u4ee5\u4f7f\u7528\u00a0select into<\/code>\u00a0\u4ee3\u66ff\u00a0create table<\/code>\uff0c\u907f\u514d\u9020\u6210\u5927\u91cf log \uff0c\u4ee5\u63d0\u9ad8\u901f\u5ea6\uff1b\u5982\u679c\u6570\u636e\u91cf\u4e0d\u5927\uff0c\u4e3a\u4e86\u7f13\u548c\u7cfb\u7edf\u8868\u7684\u8d44\u6e90\uff0c\u5e94\u5148create table<\/code>\uff0c\u7136\u540e insert\u3002<\/p>\n
        24\u3001\u5982\u679c\u4f7f\u7528\u5230\u4e86\u4e34\u65f6\u8868\uff0c\u5728\u5b58\u50a8\u8fc7\u7a0b\u7684\u6700\u540e\u52a1\u5fc5\u5c06\u6240\u6709\u7684\u4e34\u65f6\u8868\u663e\u5f0f\u5220\u9664\uff0c\u5148\u00a0truncate table<\/code>\uff0c\u7136\u540e\u00a0drop table<\/code>\uff0c\u8fd9\u6837\u53ef\u4ee5\u907f\u514d\u7cfb\u7edf\u8868\u7684\u8f83\u957f\u65f6\u95f4\u9501\u5b9a\u3002<\/p>\n
        25\u3001\u5c3d\u91cf\u907f\u514d\u4f7f\u7528\u6e38\u6807\uff0c\u56e0\u4e3a\u6e38\u6807\u7684\u6548\u7387\u8f83\u5dee\uff0c\u5982\u679c\u6e38\u6807\u64cd\u4f5c\u7684\u6570\u636e\u8d85\u8fc7 1 \u4e07\u884c\uff0c\u90a3\u4e48\u5c31\u5e94\u8be5\u8003\u8651\u6539\u5199\u3002<\/p>\n
        26\u3001\u4f7f\u7528\u57fa\u4e8e\u6e38\u6807\u7684\u65b9\u6cd5\u6216\u4e34\u65f6\u8868\u65b9\u6cd5\u4e4b\u524d\uff0c\u5e94\u5148\u5bfb\u627e\u57fa\u4e8e\u96c6\u7684\u89e3\u51b3\u65b9\u6848\u6765\u89e3\u51b3\u95ee\u9898\uff0c\u57fa\u4e8e\u96c6\u7684\u65b9\u6cd5\u901a\u5e38\u66f4\u6709\u6548\u3002<\/p>\n
        27\u3001\u4e0e\u4e34\u65f6\u8868\u4e00\u6837\uff0c\u6e38\u6807\u5e76\u4e0d\u662f\u4e0d\u53ef\u4f7f\u7528\u3002\u5bf9\u5c0f\u578b\u6570\u636e\u96c6\u4f7f\u7528 FAST_FORWARD \u6e38\u6807\u901a\u5e38\u8981\u4f18\u4e8e\u5176\u4ed6\u9010\u884c\u5904\u7406\u65b9\u6cd5\uff0c\u5c24\u5176\u662f\u5728\u5fc5\u987b\u5f15\u7528\u51e0\u4e2a\u8868\u624d\u80fd\u83b7\u5f97\u6240\u9700\u7684\u6570\u636e\u65f6\u3002\u5728\u7ed3\u679c\u96c6\u4e2d\u5305\u62ec\u201c\u5408\u8ba1\u201d\u7684\u4f8b\u7a0b\u901a\u5e38\u8981\u6bd4\u4f7f\u7528\u6e38\u6807\u6267\u884c\u7684\u901f\u5ea6\u5feb\u3002\u5982\u679c\u5f00\u53d1\u65f6 \u95f4\u5141\u8bb8\uff0c\u57fa\u4e8e\u6e38\u6807\u7684\u65b9\u6cd5\u548c\u57fa\u4e8e\u96c6\u7684\u65b9\u6cd5\u90fd\u53ef\u4ee5\u5c1d\u8bd5\u4e00\u4e0b\uff0c\u770b\u54ea\u4e00\u79cd\u65b9\u6cd5\u7684\u6548\u679c\u66f4\u597d\u3002<\/p>\n
        28\u3001\u5728\u6240\u6709\u7684\u5b58\u50a8\u8fc7\u7a0b\u548c\u89e6\u53d1\u5668\u7684\u5f00\u59cb\u5904\u8bbe\u7f6e SET NOCOUNT ON \uff0c\u5728\u7ed3\u675f\u65f6\u8bbe\u7f6e SET NOCOUNT OFF \u3002\u65e0\u9700\u5728\u6267\u884c\u5b58\u50a8\u8fc7\u7a0b\u548c\u89e6\u53d1\u5668\u7684\u6bcf\u4e2a\u8bed\u53e5\u540e\u5411\u5ba2\u6237\u7aef\u53d1\u9001 DONE_IN_PROC \u6d88\u606f\u3002<\/p>\n
        29\u3001\u5c3d\u91cf\u907f\u514d\u5927\u4e8b\u52a1\u64cd\u4f5c\uff0c\u63d0\u9ad8\u7cfb\u7edf\u5e76\u53d1\u80fd\u529b\u3002<\/p>\n
        30\u3001\u5c3d\u91cf\u907f\u514d\u5411\u5ba2\u6237\u7aef\u8fd4\u56de\u5927\u6570\u636e\u91cf\uff0c\u82e5\u6570\u636e\u91cf\u8fc7\u5927\uff0c\u5e94\u8be5\u8003\u8651\u76f8\u5e94\u9700\u6c42\u662f\u5426\u5408\u7406\u3002<\/p>\n
        \n
        \u672c\u7bc7\u6587\u7ae0\u6765\u6e90\u4e8e\u5fae\u4fe1\u516c\u4f17\u53f7: \u5168\u6808\u5ba2<\/p><\/blockquote>\n<\/div>\n","raw":"","protected":false},"excerpt":{"rendered":"
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