{"id":924,"date":"2025-04-25T14:17:00","date_gmt":"2025-04-25T06:17:00","guid":{"rendered":"https:\/\/awamyy.top\/?p=924"},"modified":"2025-05-27T15:52:43","modified_gmt":"2025-05-27T07:52:43","slug":"sql%e8%af%ad%e5%8f%a5%e9%9a%8f%e7%ac%94","status":"publish","type":"post","link":"https:\/\/awamyy.top\/?p=924","title":{"rendered":"SQL\u968f\u7b14"},"content":{"rendered":"\n<ul>\n<li class=\"has-large-font-size\"><strong>Join\u3001Inner Join\u3001Left Join\u3001Right Join\u7684\u533a\u522b<\/strong><\/li>\n<\/ul>\n\n\n\n<pre class=\"wp-block-preformatted\" style=\"font-size:16px\">1.Join\u548cinner Join\u4e00\u6837\uff0c\u8fd4\u56de\u4e24\u5f20\u8868\u5173\u8054\u5b57\u6bb5\u5171\u540c\u5b58\u5728\u7684\u8bb0\u5f55\n2.Left Join\uff0c\u4ee5\u5de6\u8868\u4e3a\u4e2d\u5fc3\uff0c\u8fd4\u56de\u5de6\u8868(test1\/a(\u522b\u540d))\u7b26\u5408\u6761\u4ef6\u7684\u8bb0\u5f55\u548c\u53f3\u8868(test2\/b(\u522b\u540d))\u4e0e\u5de6\u8868\u5173\u8054\u5b57\u6bb5(on ?=?)\u76f8\u7b49\u7684\u8bb0\u5f55\uff0c\u6ca1\u6709\u5219\u8fd4\u56de\u7a7a\n3.Right Joinn\uff0c\u4ee5\u53f3\u8868\u4e3a\u4e2d\u5fc3\uff0c\u8fd4\u56de\u53f3\u8868\u7b26\u5408\u6761\u4ef6\u7684\u8bb0\u5f55\uff0c\u548c\u5de6\u8868\u4e0e\u53f3\u8868\u5173\u8054\u5b57\u6bb5\u76f8\u7b49\u7684\u8bb0\u5f55\uff0c\u6ca1\u6709\u5219\u8fd4\u56de\n<strong>\u603b\u7ed3\u548c\u6ce8\u610f\u4e8b\u9879\uff1a<\/strong>\n1.\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u6267\u884c\uff1a\u6bcf\u4e2aLeft\/Right Join\u90fd\u662f\u57fa\u4e8e\u524d\u4e00\u6b65\u7684\u7ed3\u679c\u96c6\u8fdb\u884c\u7684\n2.\u4fdd\u7559\u5de6\/\u53f3\u8868(\u53d6\u51b3\u4e8eleft\u6216right join)\u6240\u6709\u6570\u636e\uff0c\u5373\u4f7f\u8fde\u63a5\u8868\u4e2d\u6ca1\u6709\u5339\u914d\u7684\u884c\uff0c\u4e3b\u8868\u7684\u6570\u636e\u4ecd\u4f1a\u88ab\u4fdd\u7559\uff0c\u672a\u5339\u914d\u7684\u5b57\u6bb5\u663e\u793a\u4e3a NULL<\/pre>\n\n\n\n<p style=\"font-size:16px\"><strong>\u793a\u4f8b\uff1a<\/strong>\u6709\u5982\u4e0a\u4e09\u8868\uff0c\u8981\u6c42\u67e5\u8be2\u6240\u6709\u7528\u6237\u53ca\u5176\u8ba2\u5355\u548c\u652f\u4ed8\u4fe1\u606f\uff08\u5373\u4f7f\u6ca1\u6709\u8ba2\u5355\u6216\u652f\u4ed8\u8bb0\u5f55\uff09<\/p>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-4\">\n<div class=\"wp-block-column is-vertically-aligned-top is-layout-flow\">\n<figure class=\"wp-block-table\"><table><tbody><tr><td class=\"has-text-align-left\" data-align=\"left\">userid<\/td><td>name<\/td><\/tr><tr><td class=\"has-text-align-left\" data-align=\"left\">1<\/td><td>Alice<\/td><\/tr><tr><td class=\"has-text-align-left\" data-align=\"left\">2<\/td><td>Bob<\/td><\/tr><tr><td class=\"has-text-align-left\" data-align=\"left\">3<\/td><td>Carl<\/td><\/tr><\/tbody><\/table><figcaption class=\"wp-element-caption\">user\u7528\u6237\u8868<\/figcaption><\/figure>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-vertically-aligned-top is-layout-flow\">\n<figure class=\"wp-block-table\"><table><tbody><tr><td>order_id<\/td><td>user_id<\/td><td>product<\/td><\/tr><tr><td>101<\/td><td>1<\/td><td>\u624b\u673a<\/td><\/tr><tr><td>102<\/td><td>1<\/td><td>\u8033\u673a<\/td><\/tr><tr><td>103<\/td><td>3<\/td><td>\u7b14\u8bb0\u672c<\/td><\/tr><\/tbody><\/table><figcaption class=\"wp-element-caption\"> order\u8ba2\u5355\u8868<\/figcaption><\/figure>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-vertically-aligned-top is-layout-flow\">\n<figure class=\"wp-block-table\"><table><tbody><tr><td>payment_id<\/td><td>order_id<\/td><td>amount<\/td><\/tr><tr><td>201<\/td><td>101<\/td><td>5000<\/td><\/tr><tr><td>202<\/td><td>103<\/td><td>8000<\/td><\/tr><\/tbody><\/table><figcaption class=\"wp-element-caption\">payment\u652f\u4ed8\u8868<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n<div class=\"wp-block-columns is-layout-flex wp-container-7\">\n<div class=\"wp-block-column is-vertically-aligned-top is-layout-flow\">\n<pre class=\"wp-block-code\"><code>SQL\u5982\u4e0b\uff1a\nSELECT \n    u.name AS \u7528\u6237\u540d,\n    o.product AS \u8ba2\u5355\u5546\u54c1,\n    p.amount AS \u652f\u4ed8\u91d1\u989d\nFROM user u\nLEFT JOIN order o ON u.user_id = o.user_id\nLEFT JOIN payment p ON o.order_id = p.order_id;<\/code><\/pre>\n<\/div>\n\n\n\n<div class=\"wp-block-column is-vertically-aligned-center is-layout-flow\">\n<figure class=\"wp-block-table\"><table><tbody><tr><td>\u7528\u6237\u540d<\/td><td>\u8ba2\u5355\u5546\u54c1<\/td><td>\u652f\u4ed8\u91d1\u989d<\/td><\/tr><tr><td>Alice<\/td><td>\u624b\u673a<\/td><td>5000<\/td><\/tr><tr><td>Alice<\/td><td>\u8033\u673a<\/td><td>NULL(\u65e0\u8033\u673a\u8ba2\u5355)<\/td><\/tr><tr><td>Bob<\/td><td>NULL(Bob\u65e0\u8ba2\u5355)<\/td><td>NULL<\/td><\/tr><tr><td>Carl<\/td><td>\u7b14\u8bb0\u672c<\/td><td>8000<\/td><\/tr><\/tbody><\/table><figcaption class=\"wp-element-caption\">\u6267\u884c\u7ed3\u679c<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n<ul>\n<li class=\"has-large-font-size\"><strong>\u7d22\u5f15<\/strong> <\/li>\n<\/ul>\n\n\n\n<p>\u4f18\u70b9\uff1a\u5bf9\u6570\u636e\u67e5\u8be2\u901f\u5ea6\u63d0\u5347\u975e\u5e38\u5927<\/p>\n\n\n\n<p>\u7f3a\u70b9\uff1a1.\u7ef4\u62a4\u7d22\u5f15\u9700\u8981\u8017\u8d39\u6570\u636e\u5e93\u8d44\u6e90\u30022.\u7d22\u5f15\u9700\u8981\u5360\u7528\u78c1\u76d8\u7a7a\u95f4\u30023.\u5f53\u8868\u6570\u636e\u88ab\u589e\u5220\u6539\u65f6\uff0c\u901f\u5ea6\u4f1a\u53d7\u5230\u5f71\u54cd\u3002\uff08\u6570\u636e\u53ef\u80fd\u4f1a\u91cd\u6392\u5e8f\uff0c\u5bfc\u81f4\u7d22\u5f15\u9700\u8981\u7ef4\u62a4\uff09<\/p>\n\n\n\n<p><strong>\u7d22\u5f15\u7684\u7c7b\u522b<\/strong>\uff08\u533a\u522b\uff1a\u53f6\u8282\u70b9\u662f\u5426\u5b58\u653e\u4e86\u884c\u6570\u636e\uff09<\/p>\n\n\n\n<ul>\n<li>\u805a\u7c07\u7d22\u5f15\uff08\u4e00\u7ea7\u7d22\u5f15\uff09\n<ul>\n<li>\u5c06\u6570\u636e\u4e0e\u7d22\u5f15\u5b58\u653e\u5728\u4e00\u8d77\uff0c\u7d22\u5f15\u7ed3\u6784\u7684\u53f6\u8282\u70b9\u4fdd\u5b58\u4e86\u884c\u6570\u636e<\/li>\n\n\n\n<li>\u5728InnoDB\u4e2d\uff0c\u5982\u679c\u8868\u6ca1\u6709\u4e3b\u952e\uff0c\u5219\u7b2c\u4e00\u4e2a\u975e\u7a7a\u4e14\u552f\u4e00\u7684\u5217\u4f5c\u4e3a\u805a\u7c07\u7d22\u5f15\u3002\u82e5\u65e0\u4e3b\u952e\u4e5f\u65e0\u975e\u7a7a\u4e14\u552f\u4e00\u7684\u5217\uff0c\u5219\u4f1a\u81ea\u52a8\u521b\u5efa\u4e00\u4e2a\u9690\u85cf\u7684row-id\u4e3a\u805a\u7c07\u7d22\u5f15<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>\u975e\u805a\u7c07\u7d22\u5f15\uff08\u4e8c\u7ea7\u7d22\u5f15\u3001\u8f85\u52a9\u7d22\u5f15\uff09\n<ul>\n<li>\u5c06\u6570\u636e\u4e0e\u7d22\u5f15\u5206\u5f00\u5b58\u653e\uff0c\u7d22\u5f15\u7ed3\u6784\u7684\u53f6\u8282\u70b9\u4fdd\u5b58\u4e86\u6307\u5411\u6570\u636e\u5bf9\u5e94\u7684\u4f4d\u7f6e(\u4e3b\u952e\u503c\/key)<\/li>\n\n\n\n<li>\u975e\u805a\u7c07\u7d22\u5f15\u67e5\u8be2\u9700\u8981\u56de\u8868\uff0c\u5373\u4ece\u4e8c\u7ea7\u7d22\u5f15\u4e2d\u62ff\u5230\u6570\u636e\u7684\u4f4d\u7f6e(\u4e3b\u952e\u503c\/key)\uff0c\u518d\u5728\u805a\u7c07\u7d22\u5f15(\u4e3b\u952e\u7d22\u5f15)\u4e2d\u67e5\u627e\u6570\u636e<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<p class=\"has-normal-font-size\"><strong>\u5b58\u50a8\u5f15\u64ce<\/strong><\/p>\n\n\n\n<ul>\n<li>InnoDB\uff08\u5fc5\u5305\u542b\u805a\u7c07\u7d22\u5f15\uff09\n<ul>\n<li>\u4e3b\u952e\u7d22\u5f15\uff1a\u5217\u88ab\u8bbe\u5b9a\u4e3a\u4e3b\u952e\u540e\uff0c\u6570\u636e\u5e93\u4f1a\u81ea\u52a8\u521b\u5efa\u7d22\u5f15\uff0c\u7d22\u5f15\u5217\u7684\u503c\u4e0d\u80fd\u4e3a\u7a7a<\/li>\n\n\n\n<li>\u5355\u503c(\u666e\u901a\u3001\u5355\u5217)\u7d22\u5f15\uff1a\u4e00\u4e2a\u7d22\u5f15\u53ea\u5305\u542b\u5355\u4e2a\u5217\uff0c\u4e00\u4e2a\u8868\u53ef\u4ee5\u6709\u591a\u4e2a\u5355\u503c\u7d22\u5f15<\/li>\n\n\n\n<li>\u552f\u4e00\u7d22\u5f15\uff1a\u7d22\u5f15\u5217\u7684\u503c\u5fc5\u987b\u552f\u4e00\uff0c\u4f46\u5141\u8bb8\u4e3a\u7a7a\u503c<\/li>\n\n\n\n<li>\u590d\u5408(\u7ec4\u5408)\u7d22\u5f15\uff1a\u4e00\u4e2a\u7d22\u5f15\u5305\u542b\u591a\u4e2a\u5217<\/li>\n\n\n\n<li>\u5168\u6587\u7d22\u5f15(Full Text)\uff1aMySQL5.7\u4ee5\u540e\u53ef\u7528\uff0c\u5e94\u7528\u573a\u666f\u5c11<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>MyISAM  \uff08\u4e3b\u952e\u7d22\u5f15\u3001\u4e8c\u7ea7\u7d22\u5f15\u90fd\u662f\u975e\u805a\u7c07\u7d22\u5f15\uff09<\/li>\n<\/ul>\n\n\n\n<p><strong>\u5e38\u7528\u521b\u5efa\u7d22\u5f15\u8bed\u53e5<\/strong><\/p>\n\n\n\n<ul>\n<li>&#8212; \u67e5\u770b\u7d22\u5f15<\/li>\n\n\n\n<li>SHOW INDEX FROM \u8868\u540d;<\/li>\n\n\n\n<li>&#8212; \u5220\u9664\u7d22\u5f15<\/li>\n\n\n\n<li>DROP INDEX \u7d22\u5f15\u540d on \u8868\u540d;<\/li>\n\n\n\n<li>&#8212; \u5efa\u8868\u540e\u521b\u5efa\u666e\u901a\u7d22\u5f15<\/li>\n\n\n\n<li>CREATE INDEX \u7d22\u5f15\u540d ON \u8868\u540d(\u5217\u540d);<\/li>\n\n\n\n<li>&#8212; \u5efa\u8868\u540e\u521b\u5efa\u552f\u4e00\u7d22\u5f15<\/li>\n\n\n\n<li>CREATE UNION INDEX \u7d22\u5f15\u540d ON \u8868\u540d(\u5217\u540d);<\/li>\n\n\n\n<li>&#8212; \u5efa\u8868\u540e\u521b\u5efa\u590d\u5408(\u7ec4\u5408)\u7d22\u5f15<\/li>\n\n\n\n<li>CREATE INDEX \u7ec4\u5408\u7d22\u5f15\u540d ON \u8868\u540d(\u5217\u540d1,\u5217\u540d2);<\/li>\n\n\n\n<li>&#8212; \u5efa\u8868\u65f6\u521b\u5efa\u5355\u5217(\u666e\u901a)\u7d22\u5f15\uff0c\u5176\u4e2dkey(\u5217\u540d)\u662f\u7ed9\u5217\u521b\u5efa\u521b\u5efa\u666e\u901a\u7d22\u5f15\uff0ckey()\u53ef\u4ee5\u6709\u591a\u4e2a\uff0c\u4f46\u987b\u4fdd\u8bc1\u5217\u5b58\u5728<\/li>\n\n\n\n<li>CREATE TABLE \u8868\u540d(\u5217\u540d1 VARCHAR(20) PRIMARY KEY,\u5217\u540d2 VARCHAR(20),key(\u5217\u540d2));<\/li>\n\n\n\n<li>&#8212; \u5efa\u8868\u65f6unique()\u662f\u521b\u5efa\u552f\u4e00\u7d22\u5f15<\/li>\n\n\n\n<li>CREATE TABLE \u8868\u540d(\u5217\u540d1 VARCHAR(20) PRIMARY KEY,\u5217\u540d2 VARCHAR(20),unique(\u5217\u540d2));<\/li>\n\n\n\n<li>&#8212; \u5efa\u8868\u65f6\u521b\u5efa\u590d\u5408\u7d22\u5f15<\/li>\n\n\n\n<li>CREATE TABLE \u8868\u540d(\u5217\u540d1 VARCHAR(20) PRIMARY KEY,\u5217\u540d2 VARCHAR(20),\u5217\u540d3 VARCHAR(8),key(\u5217\u540d2,\u5217\u540d3));<\/li>\n<\/ul>\n\n\n\n<p><strong>\u7d22\u5f15\u5e94\u7528<\/strong><\/p>\n\n\n\n<ul>\n<li>\u5728\u590d\u5408\u7d22\u5f15\u4e2d\u9075\u5faa<strong>\u6700\u5de6\u524d\u7f00\u539f\u5219<\/strong>\u3002\u5982\u4e0a\u793a\u4f8b\u4e2d\uff0c\u590d\u5408\u7d22\u5f15\u4e3akey(\u5217\u540d1\uff0c\u5217\u540d2)\uff0c\u5219\u67e5\u8be2\u4e2d\u5fc5\u987b\u5305\u542b\u5217\u540d1\u624d\u80fd\u4f7f\u7528\u6b64\u590d\u5408\u7d22\u5f15\u3002MySQL\u5f15\u64ce\u4f1a\u52a8\u6001\u8c03\u6574\u67e5\u8be2\u5b57\u6bb5\u987a\u5e8f\uff0c\u6240\u4ee5\u5217\u540d1\u548c\u5217\u540d2\u7684\u987a\u5e8f\u4e0d\u91cd\u8981\uff0c\u4f46\u5fc5\u987b\u5305\u542b\u5217\u540d1(\u5de6\u524d\u7f00)<\/li>\n<\/ul>\n\n\n\n<p><strong>\u65e0\u6cd5\u5e94\u7528\u7d22\u5f15\u7684\u573a\u666f<\/strong><\/p>\n\n\n\n<ul>\n<li>\u67e5\u8be2\u4e2d\u4f7f\u7528LIKE\u5173\u952e\u5b57(\u5206\u7c7b\u8ba8\u8bba)\uff1a\u5728\u67e5\u8be2\u8bed\u53e5\u4e2d\u4f7f\u7528LIKE\u5b57\u6bb5\u65f6\uff0c\u5339\u914d\u5b57\u7b26\u4e32\u7684\u7b2c\u4e00\u4e2a\u5b57\u7b26\u4e3a&#8221;%&#8221;\u65f6\uff0c\u7d22\u5f15\u5931\u6548\uff0c\u5982\u679c&#8221;%&#8221;\u4e0d\u5728\u7b2c\u4e00\u4e2a\u5b57\u7b26\uff0c\u7d22\u5f15\u80fd\u591f\u6b63\u5e38\u4f7f\u7528<\/li>\n\n\n\n<li>\u67e5\u8be2\u4e2d\u4f7f\u7528\u591a\u5217\u7d22\u5f15(\u5206\u7c7b\u8ba8\u8bba)\uff1a\u5728\u6b64\u60c5\u51b5\u4e0b\uff0c\u9075\u5faa\u6700\u5de6\u524d\u7f00\u539f\u5219<\/li>\n\n\n\n<li>\u67e5\u8be2\u4e2d\u4f7f\u7528OR\u5173\u952e\u5b57(\u5206\u7c7b\u8ba8\u8bba)\uff1a\u5728\u4f7f\u7528\u5230OR\u5173\u952e\u5b57\u65f6\uff0cOR\u524d\u540e\u5fc5\u987b\u90fd\u662f\u7d22\u5f15\u5217\uff0c\u5426\u5219\u7d22\u5f15\u5931\u6548<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>1.Join\u548cinner Join\u4e00\u6837\uff0c\u8fd4\u56de\u4e24\u5f20\u8868 \u2026<\/p>\n","protected":false},"author":1,"featured_media":925,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[41,1],"tags":[36],"_links":{"self":[{"href":"https:\/\/awamyy.top\/index.php?rest_route=\/wp\/v2\/posts\/924"}],"collection":[{"href":"https:\/\/awamyy.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/awamyy.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/awamyy.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/awamyy.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=924"}],"version-history":[{"count":109,"href":"https:\/\/awamyy.top\/index.php?rest_route=\/wp\/v2\/posts\/924\/revisions"}],"predecessor-version":[{"id":1230,"href":"https:\/\/awamyy.top\/index.php?rest_route=\/wp\/v2\/posts\/924\/revisions\/1230"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/awamyy.top\/index.php?rest_route=\/wp\/v2\/media\/925"}],"wp:attachment":[{"href":"https:\/\/awamyy.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=924"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/awamyy.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=924"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/awamyy.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=924"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}