{"id":26,"date":"2019-06-16T03:44:00","date_gmt":"2019-06-16T03:44:00","guid":{"rendered":"http:\/\/pro369.com\/Website_Design\/?p=26"},"modified":"2019-06-16T03:44:00","modified_gmt":"2019-06-16T03:44:00","slug":"mysql%e8%b3%87%e6%96%99%e5%ba%ab%e6%9f%a5%e8%a9%a2%e6%94%b9%e5%96%84%e7%9a%845%e5%80%8b%e5%a5%bd%e7%94%a8%e6%96%b9%e6%b3%95","status":"publish","type":"post","link":"https:\/\/por.tw\/Website_Design\/mysql%e8%b3%87%e6%96%99%e5%ba%ab%e6%9f%a5%e8%a9%a2%e6%94%b9%e5%96%84%e7%9a%845%e5%80%8b%e5%a5%bd%e7%94%a8%e6%96%b9%e6%b3%95\/","title":{"rendered":"MySQL\u8cc7\u6599\u5eab\u67e5\u8a62\u6539\u5584\u76845\u500b\u597d\u7528\u65b9\u6cd5"},"content":{"rendered":"

MySQL\u8cc7\u6599\u5eab\u67e5\u8a62\u6539\u5584\u76845\u500b\u597d\u7528\u65b9\u6cd5<\/strong><\/font><\/p>\n

\u4f7f\u7528PHP\u67b6\u7ad9\u6642\u6700\u5e38\u4f7f\u7528\u7684\u8cc7\u6599\u5eab\u7576\u7136\u662f\uff1aMySQL\u8cc7\u6599\u5eab\uff0c\u9019\u88e1\u4ecb\u7d39MySQL\u67e5\u8a62\u6539\u5584\u76845\u500b\u5341\u5206\u597d\u7528\u65b9\u6cd5\uff0c\u5176\u4e2d\u5167\u542b\u5982\u4f55\u6539\u5584\u8cc7\u6599\u985e\u578b\uff0c\u5c0f\u5fc3\u5b57\u96c6\u8f49\u63db\uff0c\u4ee5\u53ca\u5982\u4f55\u6539\u5584\u5b50\u67e5\u8a62\u7b49\u95dc\u806f\u5167\u5bb9\u3002
Java\u958b\u767c\u4e2d\u985e\u96b1\u85cf\u53ca\u61c9\u7528\u5834\u666f\u5206\u6790 MySQL\u8cc7\u6599\u5eab\u6240\u652f\u63f4\u7684\u4e09\u500b\u5f15\u64ce\u3002<\/p>\n

\u719f\u6089SQL\u8a9e\u53e5\u7684\u4eba\u90fd\u6e05\u695a\uff0c\u5982\u679c\u8981\u5c0d\u4e00\u500b\u4efb\u52d9\u9032\u884c\u64cd\u4f5c\u7684\u8a71\uff0cSQL\u8a9e\u53e5\u53ef\u4ee5\u6709\u5f88\u591a\u7a2e\u95dc\u806f\u5beb\u6cd5\uff0c\u4f46\u662f\u4e0d\u540c\u7684\u5beb\u6cd5\u67e5\u8a62\u7684\u6548\u80fd\u53ef\u80fd\u6703\u6709\u5929\u58e4\u4e4b\u5225\u3002<\/p>\n

\u672c\u6587\u5217\u8209\u51fa\u4e94\u500bMySQL\u67e5\u8a62\u6539\u5584\u7684\u65b9\u6cd5\uff0c\u7576\u7136\uff0c\u6539\u5584\u7684\u65b9\u6cd5\u9084\u6709\u5f88\u591a\u3002<\/strong><\/font><\/p>\n

1\u3001\u6539\u5584\u8cc7\u6599\u985e\u578b<\/strong><\/font><\/p>\n

MySQL\u4e2d\u8cc7\u6599\u985e\u578b\u6709\u591a\u7a2e\uff0c\u5982\u679c\u4f60\u662f\u4e00\u540dDBA\uff0c\u6b63\u5728\u6309\u7167\u6539\u5584\u7684\u539f\u5247\u5c0d\u8cc7\u6599\u985e\u578b\u9032\u884c\u56b4\u683c\u7684\u6aa2\u67e5\uff0c\u4f46\u958b\u767c\u4eba\u54e1\u53ef\u80fd\u6703\u9078\u53d6\u4ed6\u5011\u8a8d\u70ba\u6700\u7c21\u55ae\u7684\u5c08\u6848\uff0c\u4ee5\u52a0\u5feb\u7de8\u78bc\u901f\u5ea6\uff0c\u6216\u662f\u9078\u53d6\u6700\u660e\u986f\u7684\u9078\u53d6\uff0c\u56e0\u6b64\uff0c\u4f60\u53ef\u80fd\u9762\u81e8\u7684\u90fd\u4e0d\u662f\u6700\u4f73\u7684\u9078\u53d6\uff0c\u5982\u679c\u53ef\u80fd\u7684\u8a71\uff0c\u4f60\u61c9\u8a72\u5617\u8a66\u4ee5\u901a\u7528\u6e96\u5247\u4f86\u6539\u8b8a\u9019\u4e9b\u6c7a\u5b9a\u3002<\/p>\n

(1)\u907f\u514d\u4f7f\u7528NULL<\/strong><\/font><\/p>\n

NULL\u5c0d\u65bc\u5927\u591a\u6578\u8cc7\u6599\u5eab\u90fd\u9700\u8981\u7279\u6b8a\u8655\u7406\uff0cMySQL\u4e5f\u4e0d\u4f8b\u5916\uff0c\u5b83\u9700\u8981\u66f4\u591a\u7684\u4ee3\u78bc\uff0c\u66f4\u591a\u7684\u6aa2\u67e5\u548c\u7279\u6b8a\u7684\u7d22\u5f15\u908f\u8f2f\uff0c\u6709\u4e9b\u958b\u767c\u4eba\u54e1\u5b8c\u5168\u6c92\u6709\u610f\u8b58\u5230\uff0c\u5efa\u7acb\u8868\u6642NULL\u662f\u9810\u8a2d\u503c\uff0c\u4f46\u5927\u591a\u6578\u6642\u5019\u61c9\u8a72\u4f7f\u7528NOT NULL\uff0c\u6216\u662f\u4f7f\u7528\u4e00\u500b\u7279\u6b8a\u7684\u503c\uff0c\u59820\uff0c-1\u4f5c\u70ba\u9810\u8a2d\u503c\u3002<\/p>\n

(2)\u50c5\u53ef\u80fd\u4f7f\u7528\u66f4\u5c0f\u7684\u6b04\u4f4d<\/strong><\/font><\/p>\n

MySQL\u5f9e\u78c1\u789f\u8b80\u53d6\u8cc7\u6599\u5f8c\u662f\u5b58\u5132\u5230\u8a18\u61b6\u9ad4\u4e2d\u7684\uff0c\u7136\u5f8c\u4f7f\u7528cpu\u9031\u671f\u548c\u78c1\u789fI\/O\u8b80\u53d6\u5b83\uff0c\u9019\u610f\u5473\u8457\u8d8a\u5c0f\u7684\u8cc7\u6599\u985e\u578b\u4f54\u7528\u7684\u7a7a\u9593\u8d8a\u5c0f\uff0c\u5f9e\u78c1\u789f\u8b80\u6216\u6253\u5305\u5230\u8a18\u61b6\u9ad4\u7684\u6548\u7387\u90fd\u66f4\u597d\uff0c\u4f46\u4e5f\u4e0d\u8981\u592a\u904e\u57f7\u8457\u6e1b\u5c0f\u8cc7\u6599\u985e\u578b\uff0c\u8981\u662f\u4ee5\u5f8c\u61c9\u7528\u7a0b\u5f0f\u767c\u751f\u4ec0\u9ebc\u8b8a\u5316\u5c31\u6c92\u6709\u7a7a\u9593\u4e86\u3002\u4fee\u6539\u8868\u5c07\u9700\u8981\u91cd\u69cb\uff0c\u9593\u63a5\u5730\u53ef\u80fd\u5f15\u8d77\u4ee3\u78bc\u7684\u6539\u8b8a\uff0c\u9019\u662f\u5f88\u982d\u75bc\u7684\u554f\u984c\uff0c\u56e0\u6b64\u9700\u8981\u627e\u5230\u4e00\u500b\u5e73\u8861\u9ede\u3002<\/p>\n

2\u3001\u5c0f\u5fc3\u5b57\u96c6\u8f49\u63db<\/strong><\/font><\/p>\n

\u7528\u6236\u7aef\u6216\u61c9\u7528\u7a0b\u5f0f\u4f7f\u7528\u7684\u5b57\u96c6\u53ef\u80fd\u548c\u8868\u672c\u8eab\u7684\u5b57\u96c6\u4e0d\u4e00\u6a23\uff0c\u9019\u9700\u8981MySQL\u5728\u904b\u884c\u904e\u7a0b\u4e2d\u96b1\u542b\u5730\u9032\u884c\u8f49\u63db\uff0c\u6b64\u5916\uff0c\u8981\u78ba\u5b9a\u5b57\u96c6\u5982UTF-8\u662f\u5426\u652f\u63f4\u591a\u4f4d\u5143\u7d44\u5b57\u5143\uff0c\u56e0\u6b64\u5b83\u5011\u9700\u8981\u66f4\u591a\u7684\u5b58\u5132\u7a7a\u9593\u3002<\/p>\n

3\u3001\u6539\u5584count(my_col)\u548ccount(*)<\/strong><\/font><\/p>\n

\u5982\u679c\u4f60\u4f7f\u7528MyISAM\u8868\uff0c\u5728\u6c92\u6709where\u5b50\u53e5\u7684\u60c5\u6cc1\u4e0b\u4f7f\u7528count(*)\u901f\u5ea6\u662f\u5f88\u5feb\u7684\uff0c\u56e0\u70ba\u884c\u6578\u91cf\u7684\u7d71\u8a08\u662f\u975e\u5e38\u7cbe\u78ba\u7684\uff0c\u56e0\u6b64MySQL\u4e0d\u6703\u4e00\u884c\u4e00\u884c\u5730\u53bb\u627e\uff0c\u9032\u800c\u5f97\u51fa\u884c\u6578\uff0c\u5982my_col\u5217\u6c92\u6709\u7a7a\u503c\uff0c\u90a3\u9ebc\u548c\u524d\u9762\u8aaa\u7684\u60c5\u6cc1\u6703\u4e00\u6a23\uff0c\u5373count(my_col)\u901f\u5ea6\u4e5f\u6703\u5f88\u5feb\u3002<\/p>\n

\u5982\u679c\u6709where\u5b50\u53e5\u6642\u4f7f\u7528count( )\uff0c\u57fa\u672c\u4e0a\u5c31\u7121\u6cd5\u9032\u884c\u66f4\u591a\u6539\u5584\u4e86\uff0c\u5728where\u5b50\u53e5\u4e2d\u8d85\u51fa\u4e86\u660e\u986f\u7684\u7d22\u5f15\u5217\uff0c\u5c0d\u65bc\u8907\u96dc\u7684where\u5b50\u53e5\uff0c\u53ea\u6709\u4f7f\u7528\u8986\u84cb\u7d22\u5f15\u624d\u6709\u7528\u3002<\/p>\n

\u9664\u4e86\u4e0a\u9762\u7684\u5efa\u8b70\u5916\uff0c\u4f60\u9084\u53ef\u4ee5\u4f7f\u7528\u532f\u7e3d\u8868\uff0c\u5b83\u5011\u8b93\u4f60\u53ef\u4ee5\u5c0d\u8868\u7684\u5167\u5bb9\u4fdd\u6301\u66f4\u65b0\uff0c\u4f60\u53ef\u4ee5\u4f7f\u7528\u89f8\u767c\u5668\uff0c\u6216\u662f\u61c9\u7528\u7a0b\u5f0f\u908f\u8f2f\u4fdd\u6301\u532f\u7e3d\u8868\u7e3d\u662f\u6700\u65b0\u72c0\u614b\uff0c\u6216\u662f\u5b9a\u671f\u904b\u884c\u4e00\u500b\u6279\u8655\u7406\u4f5c\u696d\u4fdd\u6301\u586b\u5145\u6700\u65b0\u7684\u8cc7\u6599\u8a0a\u606f\uff0c\u5982\u679c\u4f60\u63a1\u7528\u5f8c\u8005\uff0c\u4f60\u7684\u8a0a\u606f\u5c07\u6703\u975e\u5e38\u63a5\u8fd1\uff0c\u4f46\u4e0d\u662f\u7cbe\u78ba\u7684\uff0c\u4f9d\u8cf4\u65bc\u6279\u8655\u7406\u4f5c\u696d\u591a\u4e45\u904b\u884c\u4e00\u6b21\uff0c\u9019\u9700\u8981\u6b0a\u8861\u61c9\u7528\u7a0b\u5f0f\u5c0d\u7cbe\u78ba\u8a0a\u606f\u7684\u9700\u8981\uff0c\u548c\u4fdd\u6301\u8cc7\u6599\u66f4\u65b0\u7684\u7cfb\u7d71\u958b\u92b7\uff0c\u8981\u5728\u9019\u4e8c\u8005\u4e4b\u9593\u627e\u5230\u4e00\u500b\u5e73\u8861\u9ede\u3002<\/p>\n

4\u3001\u6539\u5584\u5b50\u67e5\u8a62<\/strong><\/font><\/p>\n

\u9047\u5230\u5b50\u67e5\u8a62\u6642\uff0cMySQL \u67e5\u8a62\u6539\u5584\u5f15\u64ce\u4e26\u4e0d\u662f\u7e3d\u662f\u6700\u6709\u6548\u7684\uff0c\u9019\u5c31\u662f\u70ba\u4ec0\u9ebc\u7d93\u5e38\u5c07\u5b50\u67e5\u8a62\u8f49\u63db\u70ba\u9023\u7dda\u67e5\u8a62\u7684\u539f\u56e0\u4e86\uff0c\u6539\u5584\u5668\u5df2\u7d93\u80fd\u5920\u6b63\u78ba\u8655\u7406\u9023\u7dda\u67e5\u8a62\u4e86\uff0c\u7576\u7136\u8981\u6ce8\u610f\u7684\u4e00\u9ede\u662f\uff0c\u78ba\u4fdd\u9023\u7dda\u8868 (\u7b2c\u4e8c\u500b\u8868)\u7684\u9023\u7dda\u5217\u662f\u6709\u7d22\u5f15\u7684\uff0c\u5728\u7b2c\u4e00\u500b\u8868\u4e0aMySQL\u901a\u5e38\u6703\u76f8\u5c0d\u65bc\u7b2c\u4e8c\u500b\u8868\u7684\u67e5\u8a62\u5b50\u96c6\u9032\u884c\u4e00\u6b21\u5168\u8868\u6383\u7784\uff0c\u9019\u662f\u5d4c\u5957\u8ff4\u5708\u7b97\u6cd5\u7684\u4e00\u90e8\u5206\u3002

5\u3001\u6539\u5584UNION<\/strong><\/font><\/p>\n

\u5728\u8de8\u591a\u500b\u4e0d\u540c\u7684\u8cc7\u6599\u5eab\u6642\u4f7f\u7528UNION\u662f\u4e00\u500b\u6709\u8da3\u7684\u6539\u5584\u65b9\u6cd5\uff0cUNION\u5f9e\u5169\u500b\u4e92\u4e0d\u95dc\u806f\u7684\u8868\u4e2d\u8fd4\u56de\u8cc7\u6599\uff0c\u9019\u5c31\u610f\u5473\u8457\u4e0d\u6703\u51fa\u73fe\u91cd\u8907\u7684\u884c\uff0c\u540c\u6642\u4e5f\u5fc5\u9808\u5c0d\u8cc7\u6599\u9032\u884c\u6392\u5e8f\uff0c\u6211\u5011\u77e5\u9053\u6392\u5e8f\u662f\u975e\u5e38\u8017\u8cbb\u8cc7\u6e90\u7684\uff0c\u7279\u5225\u662f\u5c0d\u5927\u8868\u7684\u6392\u5e8f\u3002<\/p>\n

UNION ALL\u53ef\u4ee5\u5927\u5927\u52a0\u5feb\u901f\u5ea6\uff0c\u5982\u679c\u4f60\u5df2\u7d93\u77e5\u9053\u4f60\u7684\u8cc7\u6599\u4e0d\u6703\u5167\u542b\u91cd\u8907\u884c\uff0c\u6216\u662f\u4f60\u4e0d\u5728\u4e4e\u662f\u5426\u6703\u51fa\u73fe\u91cd\u8907\u7684\u884c\uff0c\u5728\u9019\u5169\u7a2e\u60c5\u6cc1\u4e0b\u4f7f\u7528UNION ALL\u66f4\u9069\u5408\u3002
\u6b64\u5916\uff0c\u9084\u53ef\u4ee5\u5728\u61c9\u7528\u7a0b\u5f0f\u908f\u8f2f\u4e2d\u63a1\u7528\u67d0\u4e9b\u65b9\u6cd5\u907f\u514d\u51fa\u73fe\u91cd\u8907\u7684\u884c\uff0c\u9019\u6a23UNION ALL\u548cUNION\u8fd4\u56de\u7684\u7d50\u679c\u90fd\u662f\u4e00\u6a23\u7684\uff0c\u4f46UNION ALL\u4e0d\u6703\u9032\u884c\u6392\u5e8f\u3002<\/p>\n

\u5c0f\u7d50\uff1a<\/strong><\/font>

\u96d6\u7136\u672c\u6587\u5217\u8209\u7684\u6539\u5584\u65b9\u6cd5\u4e26\u4e0d\u5b8c\u5168\uff0c\u4f46\u7121\u8ad6\u4f55\u6642\uff0c\u53ea\u8981\u53ef\u80fd\uff0c\u76e1\u53ef\u80fd\u5617\u8a66\u4e0d\u540c\u7684\u89e3\u6c7a\u5c08\u6848\uff0c\u6aa2\u8996\u67e5\u8a62\u8a08\u5283\uff0c\u5728\u5927\u8cc7\u6599\u96c6\u4e0a\u9032\u884c\u6e2c\u8a66\uff0c\u4e26\u6703\u5b9a\u4f4d\u7d50\u679c\u57fa\u6e96\u9ede\uff0c\u89c0\u5bdf\u5728\u5be6\u969b\u61c9\u7528\u4e2d\u7684\u60c5\u6cc1\u600e\u9ebc\u6a23\u3002
\u540c\u6642\uff0c\u4e8b\u5148\u6aa2\u8996\u4e00\u4e0b\u4f60\u7684\u6162\u901f\u67e5\u8a62\u65e5\u8a8c\uff0c\u76e1\u53ef\u80fd\u65e9\u5730\u627e\u51fa\u9700\u8981\u8abf\u6574\u7684\u67e5\u8a62\u3002<\/strong><\/font><\/p>\n

\u4ee5\u4e0a\u7684\u95dc\u806f\u5167\u5bb9\u5c31\u662f\u5c0d\u4e94\u500bMySQL\u67e5\u8a62\u6539\u5584\u7684\u65b9\u6cd5\u4ecb\u7d39\uff0c\u671b\u4f60\u80fd\u6709\u6240\u6536\u7a6b\u3002<\/strong><\/font><\/font><\/p>\n","protected":false},"excerpt":{"rendered":"

MySQL\u8cc7\u6599\u5eab\u67e5\u8a62\u6539\u5584\u76845\u500b\u597d\u7528\u65b9\u6cd5 \u4f7f\u7528PHP\u67b6\u7ad9\u6642\u6700\u5e38\u4f7f\u7528\u7684\u8cc7\u6599\u5eab\u7576\u7136\u662f\uff1aMySQL\u8cc7\u6599\u5eab\uff0c\u9019\u88e1\u4ecb\u7d39My […]<\/p>\n","protected":false},"author":1,"featured_media":382,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[35],"class_list":["post-26","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-16","tag-35"],"_links":{"self":[{"href":"https:\/\/por.tw\/Website_Design\/wp-json\/wp\/v2\/posts\/26","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/por.tw\/Website_Design\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/por.tw\/Website_Design\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/por.tw\/Website_Design\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/por.tw\/Website_Design\/wp-json\/wp\/v2\/comments?post=26"}],"version-history":[{"count":0,"href":"https:\/\/por.tw\/Website_Design\/wp-json\/wp\/v2\/posts\/26\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/por.tw\/Website_Design\/wp-json\/wp\/v2\/media\/382"}],"wp:attachment":[{"href":"https:\/\/por.tw\/Website_Design\/wp-json\/wp\/v2\/media?parent=26"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/por.tw\/Website_Design\/wp-json\/wp\/v2\/categories?post=26"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/por.tw\/Website_Design\/wp-json\/wp\/v2\/tags?post=26"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}