{"id":51592,"date":"2025-08-11T00:54:15","date_gmt":"2025-08-10T16:54:15","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/51592.html"},"modified":"2025-08-11T00:54:15","modified_gmt":"2025-08-10T16:54:15","slug":"sql%e7%ba%a6%e6%9d%9f%ef%bc%9a%e6%95%b0%e6%8d%ae%e5%ae%8c%e6%95%b4%e6%80%a7%e7%9a%84%e5%ae%88%e6%8a%a4%e8%80%85","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/51592.html","title":{"rendered":"SQL\u7ea6\u675f\uff1a\u6570\u636e\u5b8c\u6574\u6027\u7684\u5b88\u62a4\u8005"},"content":{"rendered":"<p>\u5728SQL\u4e2d&#xff0c;\u7ea6\u675f&#xff08;Constraints&#xff09; \u662f\u4f5c\u7528\u4e8e\u6570\u636e\u5e93\u8868\u5b57\u6bb5\u4e0a\u7684\u89c4\u5219&#xff0c;\u7528\u4e8e\u5f3a\u5236\u4fdd\u8bc1\u6570\u636e\u7684\u5b8c\u6574\u6027\u3001\u51c6\u786e\u6027\u548c\u4e00\u81f4\u6027\u3002\u5f53\u63d2\u5165\u3001\u66f4\u65b0\u6216\u5220\u9664\u6570\u636e\u65f6&#xff0c;\u7ea6\u675f\u4f1a\u81ea\u52a8\u9a8c\u8bc1\u64cd\u4f5c\u662f\u5426\u7b26\u5408\u89c4\u5219&#xff0c;\u82e5\u8fdd\u53cd\u5219\u62d2\u7edd\u6267\u884c\u3002<\/p>\n<p>\u4ee5\u4e0b\u662fSQL\u4e2d\u5e38\u89c1\u7684\u7ea6\u675f\u7c7b\u578b\u53ca\u5176\u4f5c\u7528&#xff1a;<\/p>\n<hr \/>\n<h4>&#x1f4cc; 1. PRIMARY KEY&#xff08;\u4e3b\u952e\u7ea6\u675f&#xff09;<\/h4>\n<ul>\n<li>\u4f5c\u7528&#xff1a;\u552f\u4e00\u6807\u8bc6\u8868\u4e2d\u7684\u6bcf\u4e00\u6761\u8bb0\u5f55&#xff08;\u7c7b\u4f3c\u8eab\u4efd\u8bc1\u53f7&#xff09;\u3002<\/li>\n<li>\u7279\u70b9&#xff1a;\n<ul>\n<li>\u552f\u4e00\u6027&#xff1a;\u503c\u4e0d\u53ef\u91cd\u590d\u3002<\/li>\n<li>\u975e\u7a7a\u6027&#xff1a;\u503c\u4e0d\u53ef\u4e3a NULL\u3002<\/li>\n<li>\u4e00\u4e2a\u8868\u53ea\u80fd\u6709\u4e00\u4e2a\u4e3b\u952e&#xff08;\u53ef\u7531\u5355\u5217\u6216\u591a\u5217\u7ec4\u5408&#xff09;\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><span class=\"token keyword\">CREATE<\/span> <span class=\"token keyword\">TABLE<\/span> Users <span class=\"token punctuation\">(<\/span><br \/>\n    id <span class=\"token keyword\">INT<\/span> <span class=\"token keyword\">PRIMARY<\/span> <span class=\"token keyword\">KEY<\/span><span class=\"token punctuation\">,<\/span>  <span class=\"token comment\">&#8212; \u5355\u5217\u4e3b\u952e<\/span><br \/>\n    name <span class=\"token keyword\">VARCHAR<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">50<\/span><span class=\"token punctuation\">)<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token comment\">&#8212; \u591a\u5217\u7ec4\u5408\u4e3b\u952e<\/span><br \/>\n<span class=\"token keyword\">CREATE<\/span> <span class=\"token keyword\">TABLE<\/span> Orders <span class=\"token punctuation\">(<\/span><br \/>\n    order_id <span class=\"token keyword\">INT<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    product_id <span class=\"token keyword\">INT<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token keyword\">PRIMARY<\/span> <span class=\"token keyword\">KEY<\/span> <span class=\"token punctuation\">(<\/span>order_id<span class=\"token punctuation\">,<\/span> product_id<span class=\"token punctuation\">)<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<hr \/>\n<h4>&#x1f4cc; 2. FOREIGN KEY&#xff08;\u5916\u952e\u7ea6\u675f&#xff09;<\/h4>\n<ul>\n<li>\u4f5c\u7528&#xff1a;\u786e\u4fdd\u8868\u95f4\u6570\u636e\u5173\u8054\u7684\u5b8c\u6574\u6027&#xff08;\u5982\u8ba2\u5355\u5fc5\u987b\u5c5e\u4e8e\u5b58\u5728\u7684\u7528\u6237&#xff09;\u3002<\/li>\n<li>\u7279\u70b9&#xff1a;\n<ul>\n<li>\u6307\u5411\u53e6\u4e00\u5f20\u8868\u7684\u4e3b\u952e\u6216\u552f\u4e00\u952e\u3002<\/li>\n<li>\u53ef\u5b9a\u4e49\u7ea7\u8054\u64cd\u4f5c&#xff08;\u5982 ON DELETE CASCADE&#xff1a;\u4e3b\u8868\u5220\u9664\u65f6&#xff0c;\u81ea\u52a8\u5220\u9664\u4ece\u8868\u5173\u8054\u6570\u636e&#xff09;\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><span class=\"token keyword\">CREATE<\/span> <span class=\"token keyword\">TABLE<\/span> Orders <span class=\"token punctuation\">(<\/span><br \/>\n    order_id <span class=\"token keyword\">INT<\/span> <span class=\"token keyword\">PRIMARY<\/span> <span class=\"token keyword\">KEY<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    user_id <span class=\"token keyword\">INT<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token comment\">&#8212; \u5173\u8054Users\u8868\u7684\u4e3b\u952eid<\/span><br \/>\n    <span class=\"token keyword\">FOREIGN<\/span> <span class=\"token keyword\">KEY<\/span> <span class=\"token punctuation\">(<\/span>user_id<span class=\"token punctuation\">)<\/span> <span class=\"token keyword\">REFERENCES<\/span> Users<span class=\"token punctuation\">(<\/span>id<span class=\"token punctuation\">)<\/span><br \/>\n    <span class=\"token keyword\">ON<\/span> <span class=\"token keyword\">DELETE<\/span> <span class=\"token keyword\">CASCADE<\/span>  <span class=\"token comment\">&#8212; \u7528\u6237\u5220\u9664\u65f6&#xff0c;\u5176\u8ba2\u5355\u81ea\u52a8\u5220\u9664<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<hr \/>\n<h4>&#x1f4cc; 3. UNIQUE&#xff08;\u552f\u4e00\u7ea6\u675f&#xff09;<\/h4>\n<ul>\n<li>\u4f5c\u7528&#xff1a;\u786e\u4fdd\u5b57\u6bb5\u503c\u5728\u8868\u5185\u552f\u4e00&#xff08;\u5141\u8bb8\u7a7a\u503c&#xff09;\u3002<\/li>\n<li>\u7279\u70b9&#xff1a;\n<ul>\n<li>\u4e00\u4e2a\u8868\u53ef\u6709\u591a\u4e2a\u552f\u4e00\u7ea6\u675f\u3002<\/li>\n<li>\u4e0e\u4e3b\u952e\u533a\u522b&#xff1a;\u5141\u8bb8 NULL \u503c&#xff08;\u4e3b\u952e\u4e0d\u5141\u8bb8&#xff09;\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><span class=\"token keyword\">CREATE<\/span> <span class=\"token keyword\">TABLE<\/span> Employees <span class=\"token punctuation\">(<\/span><br \/>\n    id <span class=\"token keyword\">INT<\/span> <span class=\"token keyword\">PRIMARY<\/span> <span class=\"token keyword\">KEY<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    email <span class=\"token keyword\">VARCHAR<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">100<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token keyword\">UNIQUE<\/span>  <span class=\"token comment\">&#8212; \u90ae\u7bb1\u5fc5\u987b\u552f\u4e00<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<hr \/>\n<h4>&#x1f4cc; 4. NOT NULL&#xff08;\u975e\u7a7a\u7ea6\u675f&#xff09;<\/h4>\n<ul>\n<li>\u4f5c\u7528&#xff1a;\u5f3a\u5236\u5b57\u6bb5\u4e0d\u5141\u8bb8\u5b58\u5165 NULL \u503c&#xff08;\u5fc5\u987b\u63d0\u4f9b\u6709\u6548\u6570\u636e&#xff09;\u3002<\/li>\n<li>\u5e38\u89c1\u573a\u666f&#xff1a;\u5173\u952e\u5b57\u6bb5\u5982\u59d3\u540d\u3001\u8ba2\u5355\u53f7\u7b49\u3002<\/li>\n<\/ul>\n<p><span class=\"token keyword\">CREATE<\/span> <span class=\"token keyword\">TABLE<\/span> Products <span class=\"token punctuation\">(<\/span><br \/>\n    id <span class=\"token keyword\">INT<\/span> <span class=\"token keyword\">PRIMARY<\/span> <span class=\"token keyword\">KEY<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    name <span class=\"token keyword\">VARCHAR<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">50<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">NOT<\/span> <span class=\"token boolean\">NULL<\/span>  <span class=\"token comment\">&#8212; \u4ea7\u54c1\u540d\u4e0d\u80fd\u4e3a\u7a7a<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<hr \/>\n<h4>&#x1f4cc; 5. CHECK&#xff08;\u68c0\u67e5\u7ea6\u675f&#xff09;<\/h4>\n<ul>\n<li>\u4f5c\u7528&#xff1a;\u81ea\u5b9a\u4e49\u6761\u4ef6\u6821\u9a8c\u5b57\u6bb5\u503c&#xff08;\u5982\u5e74\u9f84\u8303\u56f4\u3001\u6570\u503c\u6b63\u8d1f&#xff09;\u3002<\/li>\n<\/ul>\n<p><span class=\"token keyword\">CREATE<\/span> <span class=\"token keyword\">TABLE<\/span> Students <span class=\"token punctuation\">(<\/span><br \/>\n    id <span class=\"token keyword\">INT<\/span> <span class=\"token keyword\">PRIMARY<\/span> <span class=\"token keyword\">KEY<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    age <span class=\"token keyword\">INT<\/span> <span class=\"token keyword\">CHECK<\/span> <span class=\"token punctuation\">(<\/span>age <span class=\"token operator\">&gt;&#061;<\/span> <span class=\"token number\">18<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span>  <span class=\"token comment\">&#8212; \u5e74\u9f84\u5fc5\u987b\u226518<\/span><br \/>\n    grade <span class=\"token keyword\">CHAR<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token keyword\">CHECK<\/span> <span class=\"token punctuation\">(<\/span>grade <span class=\"token operator\">IN<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token string\">&#039;A&#039;<\/span><span class=\"token punctuation\">,<\/span><span class=\"token string\">&#039;B&#039;<\/span><span class=\"token punctuation\">,<\/span><span class=\"token string\">&#039;C&#039;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span>  <span class=\"token comment\">&#8212; \u7b49\u7ea7\u53ea\u80fd\u662fA,B,C<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<hr \/>\n<h4>&#x1f4cc; 6. DEFAULT&#xff08;\u9ed8\u8ba4\u503c\u7ea6\u675f&#xff09;<\/h4>\n<ul>\n<li>\u4f5c\u7528&#xff1a;\u5f53\u63d2\u5165\u6570\u636e\u672a\u6307\u5b9a\u5b57\u6bb5\u503c\u65f6&#xff0c;\u81ea\u52a8\u586b\u5145\u9884\u8bbe\u503c\u3002<\/li>\n<\/ul>\n<p><span class=\"token keyword\">CREATE<\/span> <span class=\"token keyword\">TABLE<\/span> Orders <span class=\"token punctuation\">(<\/span><br \/>\n    id <span class=\"token keyword\">INT<\/span> <span class=\"token keyword\">PRIMARY<\/span> <span class=\"token keyword\">KEY<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    order_date <span class=\"token keyword\">DATE<\/span> <span class=\"token keyword\">DEFAULT<\/span> <span class=\"token keyword\">CURRENT_DATE<\/span>  <span class=\"token comment\">&#8212; \u672a\u6307\u5b9a\u65e5\u671f\u65f6\u81ea\u52a8\u7528\u5f53\u524d\u65e5\u671f<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<hr \/>\n<h4>\u26a0\ufe0f \u7ea6\u675f\u7684\u6ce8\u610f\u4e8b\u9879<\/h4>\n<li>\u547d\u540d\u7ea6\u675f&#xff1a;\u663e\u5f0f\u547d\u540d\u4fbf\u4e8e\u7ef4\u62a4&#xff08;\u5426\u5219\u6570\u636e\u5e93\u81ea\u52a8\u751f\u6210\u968f\u673a\u540d&#xff09;\u3002<span class=\"token keyword\">CREATE<\/span> <span class=\"token keyword\">TABLE<\/span> Users <span class=\"token punctuation\">(<\/span><br \/>\n    id <span class=\"token keyword\">INT<\/span><span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token keyword\">CONSTRAINT<\/span> pk_users <span class=\"token keyword\">PRIMARY<\/span> <span class=\"token keyword\">KEY<\/span> <span class=\"token punctuation\">(<\/span>id<span class=\"token punctuation\">)<\/span>  <span class=\"token comment\">&#8212; \u547d\u540d\u4e3b\u952e\u7ea6\u675f<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<\/li>\n<li>\u4fee\u6539\u7ea6\u675f&#xff1a;\u53ef\u901a\u8fc7 ALTER TABLE \u589e\u5220\u7ea6\u675f\u3002<span class=\"token keyword\">ALTER<\/span> <span class=\"token keyword\">TABLE<\/span> Employees <span class=\"token keyword\">ADD<\/span> <span class=\"token keyword\">CONSTRAINT<\/span> chk_salary <span class=\"token keyword\">CHECK<\/span> <span class=\"token punctuation\">(<\/span>salary <span class=\"token operator\">&gt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token keyword\">ALTER<\/span> <span class=\"token keyword\">TABLE<\/span> Employees <span class=\"token keyword\">DROP<\/span> <span class=\"token keyword\">CONSTRAINT<\/span> chk_salary<span class=\"token punctuation\">;<\/span><\/p>\n<\/li>\n<li>\u6027\u80fd\u5f71\u54cd&#xff1a;\u5916\u952e\u548c\u552f\u4e00\u7ea6\u675f\u4f1a\u81ea\u52a8\u521b\u5efa\u7d22\u5f15&#xff0c;\u53ef\u80fd\u5f71\u54cd\u5199\u5165\u901f\u5ea6&#xff0c;\u4f46\u63d0\u5347\u67e5\u8be2\u6548\u7387\u3002<\/li>\n<hr \/>\n<h4>&#x1f4a1; \u5e94\u7528\u573a\u666f\u793a\u4f8b<\/h4>\n<table>\n<tr>\u7ea6\u675f\u7c7b\u578b\u5b9e\u9645\u5e94\u7528\u573a\u666f<\/tr>\n<tbody>\n<tr>\n<td>PRIMARY KEY<\/td>\n<td>\u7528\u6237ID\u3001\u8ba2\u5355\u53f7\u7b49\u552f\u4e00\u6807\u8bc6\u5b57\u6bb5<\/td>\n<\/tr>\n<tr>\n<td>FOREIGN KEY<\/td>\n<td>\u8ba2\u5355\u5173\u8054\u7528\u6237ID\u3001\u8bc4\u8bba\u5173\u8054\u6587\u7ae0ID<\/td>\n<\/tr>\n<tr>\n<td>UNIQUE<\/td>\n<td>\u7528\u6237\u90ae\u7bb1\u3001\u624b\u673a\u53f7\u7b49\u4e0d\u53ef\u91cd\u590d\u7684\u4e1a\u52a1\u5b57\u6bb5<\/td>\n<\/tr>\n<tr>\n<td>NOT NULL<\/td>\n<td>\u5fc5\u586b\u9879&#xff08;\u5982\u7528\u6237\u540d\u3001\u521b\u5efa\u65f6\u95f4&#xff09;<\/td>\n<\/tr>\n<tr>\n<td>CHECK<\/td>\n<td>\u4ef7\u683c\u22650\u3001\u6027\u522b\u53ea\u80fd\u662f\u2019M\u2019\u6216\u2019F\u2019\u7b49\u903b\u8f91\u6821\u9a8c<\/td>\n<\/tr>\n<tr>\n<td>DEFAULT<\/td>\n<td>\u81ea\u52a8\u586b\u5145\u521b\u5efa\u65f6\u95f4\u3001\u72b6\u6001\u9ed8\u8ba4\u503c<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u5408\u7406\u4f7f\u7528\u7ea6\u675f\u53ef\u907f\u514d\u810f\u6570\u636e&#xff08;\u5982\u65e0\u6548\u5916\u952e\u3001\u91cd\u590d\u8ba2\u5355\u53f7&#xff09;&#xff0c;\u662f\u6570\u636e\u5e93\u8bbe\u8ba1\u7684\u6838\u5fc3\u73af\u8282&#xff01;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb168\u6b21\u3002SQL\u7ea6\u675f\u662f\u7528\u4e8e\u4fdd\u8bc1\u6570\u636e\u5b8c\u6574\u6027\u548c\u4e00\u81f4\u6027\u7684\u91cd\u8981\u89c4\u5219\uff0c\u4e3b\u8981\u5305\u62ec6\u79cd\u7c7b\u578b\uff1a1. \u4e3b\u952e(PRIMARY KEY) &#8211; 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