{"id":78056,"date":"2024-10-16T11:26:16","date_gmt":"2024-10-16T03:26:16","guid":{"rendered":"https:\/\/server.hk\/cnblog\/78056\/"},"modified":"2024-10-16T11:26:16","modified_gmt":"2024-10-16T03:26:16","slug":"mysql%e6%8c%87%e4%bb%a4-constraint%ef%bc%88%e7%b4%84%e6%9d%9f%ef%bc%89","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/78056\/","title":{"rendered":"MySQL\u6307\u4ee4: CONSTRAINT\uff08\u7d04\u675f\uff09"},"content":{"rendered":"<h1 id=\"mysql%e6%8c%87%e4%bb%a4-constraint%ef%bc%88%e7%b4%84%e6%9d%9f%ef%bc%89-SPWWwVsWlm\">MySQL\u6307\u4ee4: CONSTRAINT\uff08\u7d04\u675f\uff09<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0c\u7d04\u675f\uff08CONSTRAINT\uff09\u662f\u7528\u4f86\u9650\u5236\u8cc7\u6599\u8868\u4e2d\u8cc7\u6599\u7684\u6709\u6548\u6027\u548c\u5b8c\u6574\u6027\u7684\u91cd\u8981\u5de5\u5177\u3002MySQL\u4f5c\u70ba\u4e00\u500b\u6d41\u884c\u7684\u958b\u6e90\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\uff0c\u63d0\u4f9b\u4e86\u591a\u7a2e\u7d04\u675f\u985e\u578b\uff0c\u4ee5\u78ba\u4fdd\u8cc7\u6599\u7684\u6b63\u78ba\u6027\u548c\u4e00\u81f4\u6027\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0eMySQL\u4e2d\u7684\u7d04\u675f\u985e\u578b\u53ca\u5176\u4f7f\u7528\u65b9\u6cd5\u3002<\/p>\n<h2 id=\"%e7%b4%84%e6%9d%9f%e7%9a%84%e9%a1%9e%e5%9e%8b-SPWWwVsWlm\">\u7d04\u675f\u7684\u985e\u578b<\/h2>\n<p>MySQL\u652f\u6301\u591a\u7a2e\u7d04\u675f\uff0c\u4e3b\u8981\u5305\u62ec\u4ee5\u4e0b\u5e7e\u7a2e\uff1a<\/p>\n<ul>\n<li><strong>NOT NULL<\/strong>: \u78ba\u4fdd\u67d0\u500b\u6b04\u4f4d\u4e0d\u80fd\u70ba\u7a7a\u3002<\/li>\n<li><strong>UNIQUE<\/strong>: \u78ba\u4fdd\u67d0\u500b\u6b04\u4f4d\u7684\u503c\u5728\u8cc7\u6599\u8868\u4e2d\u662f\u552f\u4e00\u7684\u3002<\/li>\n<li><strong>PRIMARY KEY<\/strong>: \u7d44\u5408\u4e86NOT NULL\u548cUNIQUE\u7684\u7279\u6027\uff0c\u7528\u65bc\u552f\u4e00\u6a19\u8b58\u8cc7\u6599\u8868\u4e2d\u7684\u6bcf\u4e00\u884c\u3002<\/li>\n<li><strong>FOREIGN KEY<\/strong>: \u7528\u65bc\u5efa\u7acb\u8207\u5176\u4ed6\u8cc7\u6599\u8868\u7684\u95dc\u806f\uff0c\u78ba\u4fdd\u8cc7\u6599\u7684\u53c3\u7167\u5b8c\u6574\u6027\u3002<\/li>\n<li><strong>CHECK<\/strong>: \u7528\u65bc\u9650\u5236\u6b04\u4f4d\u7684\u503c\u5fc5\u9808\u6eff\u8db3\u7279\u5b9a\u689d\u4ef6\u3002<\/li>\n<\/ul>\n<h2 id=\"%e4%bd%bf%e7%94%a8%e7%af%84%e4%be%8b-SPWWwVsWlm\">\u4f7f\u7528\u7bc4\u4f8b<\/h2>\n<h3 id=\"1-not-null-%e7%b4%84%e6%9d%9f-SPWWwVsWlm\">1. NOT NULL \u7d04\u675f<\/h3>\n<p>\u5728\u5275\u5efa\u8cc7\u6599\u8868\u6642\uff0c\u53ef\u4ee5\u4f7f\u7528NOT NULL\u7d04\u675f\u4f86\u78ba\u4fdd\u67d0\u500b\u6b04\u4f4d\u4e0d\u6703\u70ba\u7a7a\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>CREATE TABLE users (\n    id INT AUTO_INCREMENT,\n    username VARCHAR(50) NOT NULL,\n    email VARCHAR(100) NOT NULL,\n    PRIMARY KEY (id)\n);<\/code><\/pre>\n<h3 id=\"2-unique-%e7%b4%84%e6%9d%9f-SPWWwVsWlm\">2. UNIQUE \u7d04\u675f<\/h3>\n<p>\u5982\u679c\u5e0c\u671b\u67d0\u500b\u6b04\u4f4d\u7684\u503c\u5728\u8cc7\u6599\u8868\u4e2d\u662f\u552f\u4e00\u7684\uff0c\u53ef\u4ee5\u4f7f\u7528UNIQUE\u7d04\u675f\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>CREATE TABLE products (\n    id INT AUTO_INCREMENT,\n    product_name VARCHAR(100) NOT NULL,\n    sku VARCHAR(50) UNIQUE,\n    PRIMARY KEY (id)\n);<\/code><\/pre>\n<h3 id=\"3-primary-key-%e7%b4%84%e6%9d%9f-SPWWwVsWlm\">3. PRIMARY KEY \u7d04\u675f<\/h3>\n<p>PRIMARY KEY\u7d04\u675f\u7528\u65bc\u552f\u4e00\u6a19\u8b58\u8cc7\u6599\u8868\u4e2d\u7684\u6bcf\u4e00\u884c\uff0c\u901a\u5e38\u6703\u5728\u5275\u5efa\u8cc7\u6599\u8868\u6642\u6307\u5b9a\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>CREATE TABLE orders (\n    order_id INT AUTO_INCREMENT,\n    user_id INT NOT NULL,\n    order_date DATETIME NOT NULL,\n    PRIMARY KEY (order_id)\n);<\/code><\/pre>\n<h3 id=\"4-foreign-key-%e7%b4%84%e6%9d%9f-SPWWwVsWlm\">4. FOREIGN KEY \u7d04\u675f<\/h3>\n<p>FOREIGN KEY\u7d04\u675f\u7528\u65bc\u5efa\u7acb\u8cc7\u6599\u8868\u4e4b\u9593\u7684\u95dc\u806f\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>CREATE TABLE order_items (\n    item_id INT AUTO_INCREMENT,\n    order_id INT,\n    product_id INT,\n    PRIMARY KEY (item_id),\n    FOREIGN KEY (order_id) REFERENCES orders(order_id)\n);<\/code><\/pre>\n<h3 id=\"5-check-%e7%b4%84%e6%9d%9f-SPWWwVsWlm\">5. CHECK \u7d04\u675f<\/h3>\n<p>CHECK\u7d04\u675f\u7528\u65bc\u9650\u5236\u6b04\u4f4d\u7684\u503c\u5fc5\u9808\u6eff\u8db3\u7279\u5b9a\u689d\u4ef6\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>CREATE TABLE employees (\n    employee_id INT AUTO_INCREMENT,\n    salary DECIMAL(10, 2),\n    PRIMARY KEY (employee_id),\n    CHECK (salary &gt; 0)\n);<\/code><\/pre>\n<h2 id=\"%e7%b4%84%e6%9d%9f%e7%9a%84%e4%bf%ae%e6%94%b9%e8%88%87%e5%88%aa%e9%99%a4-SPWWwVsWlm\">\u7d04\u675f\u7684\u4fee\u6539\u8207\u522a\u9664<\/h2>\n<p>\u5728MySQL\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528ALTER TABLE\u6307\u4ee4\u4f86\u4fee\u6539\u6216\u522a\u9664\u7d04\u675f\u3002\u4f8b\u5982\uff0c\u82e5\u8981\u522a\u9664UNIQUE\u7d04\u675f\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u6307\u4ee4\uff1a<\/p>\n<pre><code>ALTER TABLE products\nDROP INDEX sku;<\/code><\/pre>\n<p>\u82e5\u8981\u6dfb\u52a0\u65b0\u7684\u7d04\u675f\uff0c\u53ef\u4ee5\u4f7f\u7528\uff1a<\/p>\n<pre><code>ALTER TABLE employees\nADD CONSTRAINT chk_salary CHECK (salary &gt; 0);<\/code><\/pre>\n<h2 id=\"%e7%b8%bd%e7%b5%90-SPWWwVsWlm\">\u7e3d\u7d50<\/h2>\n<p>MySQL\u4e2d\u7684\u7d04\u675f\u662f\u78ba\u4fdd\u8cc7\u6599\u5b8c\u6574\u6027\u548c\u6b63\u78ba\u6027\u7684\u91cd\u8981\u5de5\u5177\u3002\u900f\u904e\u4f7f\u7528NOT NULL\u3001UNIQUE\u3001PRIMARY KEY\u3001FOREIGN KEY\u548cCHECK\u7b49\u7d04\u675f\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u6709\u6548\u5730\u7ba1\u7406\u8cc7\u6599\u5eab\u4e2d\u7684\u8cc7\u6599\u3002\u4e86\u89e3\u9019\u4e9b\u7d04\u675f\u7684\u4f7f\u7528\u65b9\u6cd5\uff0c\u5c07\u6709\u52a9\u65bc\u63d0\u5347\u8cc7\u6599\u5eab\u7684\u8a2d\u8a08\u8cea\u91cf\u548c\u904b\u884c\u6548\u7387\u3002<\/p>\n<p>\u5982\u9700\u9032\u4e00\u6b65\u4e86\u89e3\u5982\u4f55\u5728\u60a8\u7684 <a href=\"https:\/\/server.hk\">\u9999\u6e2fVPS<\/a> \u4e0a\u4f7f\u7528MySQL\uff0c\u8acb\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4ee5\u7372\u53d6\u66f4\u591a\u8cc7\u8a0a\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3MySQL\u4e2d\u7684CONSTRAINT\uff08\u7d04\u675f\uff09\u6307\u4ee4\uff0c\u5b78\u7fd2\u5982\u4f55\u5f37\u5316\u6578\u64da\u5b8c\u6574\u6027\u548c\u5b9a\u7fa9\u8868\u4e4b\u9593\u7684\u95dc\u4fc2\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-78056","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/78056","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=78056"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/78056\/revisions"}],"predecessor-version":[{"id":78057,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/78056\/revisions\/78057"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=78056"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=78056"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=78056"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}