{"id":1790,"date":"2025-02-18T22:51:46","date_gmt":"2025-02-18T14:51:46","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=1790"},"modified":"2025-02-18T22:51:46","modified_gmt":"2025-02-18T14:51:46","slug":"mysql-alter-%e5%91%bd%e4%bb%a4","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/02\/18\/mysql-alter-%e5%91%bd%e4%bb%a4\/","title":{"rendered":"MySQL ALTER \u547d\u4ee4"},"content":{"rendered":"\n

\u5728 MySQL \u4e2d\uff0cALTER<\/code> \u547d\u4ee4\u7528\u4e8e\u4fee\u6539\u6570\u636e\u5e93\u5bf9\u8c61\u7684\u7ed3\u6784\uff0c\u7279\u522b\u662f\u7528\u4e8e\u4fee\u6539\u8868\u7684\u7ed3\u6784\u3002\u4f7f\u7528 ALTER<\/code> \u53ef\u4ee5\u5bf9\u8868\u7684\u5217\u3001\u7d22\u5f15\u3001\u7ea6\u675f\u7b49\u8fdb\u884c\u4fee\u6539\u3002\u8fd9\u4e2a\u547d\u4ee4\u975e\u5e38\u5f3a\u5927\uff0c\u4f46\u8981\u5c0f\u5fc3\u4f7f\u7528\uff0c\u56e0\u4e3a\u5b83\u53ef\u80fd\u4f1a\u5f71\u54cd\u73b0\u6709\u6570\u636e\u548c\u5e94\u7528\u7a0b\u5e8f\u3002<\/p>\n\n\n\n

1. ALTER \u8868\u7684\u57fa\u672c\u8bed\u6cd5<\/strong><\/h3>\n\n\n\n
ALTER TABLE table_name action;<\/code><\/pre>\n\n\n\n
    \n
  • table_name<\/code>\uff1a\u8981\u4fee\u6539\u7684\u8868\u7684\u540d\u79f0\u3002<\/li>\n\n\n\n
  • action<\/code>\uff1a\u5b9a\u4e49\u8981\u5bf9\u8868\u8fdb\u884c\u7684\u64cd\u4f5c\u3002<\/li>\n<\/ul>\n\n\n\n
    2. \u5e38\u89c1\u7684 ALTER \u64cd\u4f5c<\/strong><\/h3>\n\n\n\n
    2.1 \u4fee\u6539\u5217\uff08\u4fee\u6539\u5217\u7684\u6570\u636e\u7c7b\u578b\u3001\u540d\u79f0\u3001\u9ed8\u8ba4\u503c\u7b49\uff09<\/h4>\n\n\n\n
    \u4f60\u53ef\u4ee5\u901a\u8fc7 MODIFY COLUMN<\/code> \u6765\u4fee\u6539\u5217\u7684\u6570\u636e\u7c7b\u578b\u6216\u8005\u5176\u4ed6\u5c5e\u6027\u3002<\/p>\n\n\n\n
    \u4fee\u6539\u5217\u7684\u6570\u636e\u7c7b\u578b\uff1a<\/strong><\/p>\n\n\n\n
    ALTER TABLE employees MODIFY COLUMN emp_age INT;<\/code><\/pre>\n\n\n\n
    \u6b64\u547d\u4ee4\u5c06 emp_age<\/code> \u5217\u7684\u6570\u636e\u7c7b\u578b\u4fee\u6539\u4e3a INT<\/code>\u3002<\/p>\n\n\n\n
    \u4fee\u6539\u5217\u7684\u540d\u79f0\uff1a<\/strong><\/p>\n\n\n\n
    ALTER TABLE employees CHANGE COLUMN emp_age employee_age INT;<\/code><\/pre>\n\n\n\n
    \u8fd9\u91cc\uff0cCHANGE COLUMN<\/code> \u7528\u4e8e\u4fee\u6539\u5217\u540d\uff0c\u539f\u5217\u540d\u662f emp_age<\/code>\uff0c\u65b0\u5217\u540d\u662f employee_age<\/code>\uff0c\u5e76\u4e14\u6570\u636e\u7c7b\u578b\u4fdd\u6301\u4e3a INT<\/code>\u3002<\/p>\n\n\n\n
    2.2 \u6dfb\u52a0\u5217<\/h4>\n\n\n\n
    \u4f7f\u7528 ADD COLUMN<\/code> \u53ef\u4ee5\u5411\u8868\u4e2d\u6dfb\u52a0\u65b0\u7684\u5217\u3002<\/p>\n\n\n\n
    ALTER TABLE employees ADD COLUMN emp_email VARCHAR(255);<\/code><\/pre>\n\n\n\n
    \u8fd9\u5c06\u5728 employees<\/code> \u8868\u4e2d\u6dfb\u52a0\u4e00\u4e2a\u65b0\u7684\u5217 emp_email<\/code>\uff0c\u6570\u636e\u7c7b\u578b\u4e3a VARCHAR(255)<\/code>\u3002<\/p>\n\n\n\n
    \u6ce8\u610f\uff1a<\/strong> \u5982\u679c\u4f60\u60f3\u5728\u6307\u5b9a\u4f4d\u7f6e\u6dfb\u52a0\u5217\uff0c\u53ef\u4ee5\u4f7f\u7528 FIRST<\/code> \u6216 AFTER<\/code>\u3002<\/p>\n\n\n\n
    ALTER TABLE employees ADD COLUMN emp_phone VARCHAR(20) AFTER emp_email;<\/code><\/pre>\n\n\n\n
    \u8fd9\u4f1a\u5c06 emp_phone<\/code> \u5217\u6dfb\u52a0\u5230 emp_email<\/code> \u5217\u540e\u9762\u3002<\/p>\n\n\n\n
    2.3 \u5220\u9664\u5217<\/h4>\n\n\n\n
    \u4f7f\u7528 DROP COLUMN<\/code> \u5220\u9664\u8868\u4e2d\u7684\u67d0\u4e00\u5217\u3002<\/p>\n\n\n\n
    ALTER TABLE employees DROP COLUMN emp_phone;<\/code><\/pre>\n\n\n\n
    \u6b64\u547d\u4ee4\u5c06\u5220\u9664 employees<\/code> \u8868\u4e2d\u7684 emp_phone<\/code> \u5217\u3002<\/p>\n\n\n\n
    2.4 \u4fee\u6539\u5217\u7684\u9ed8\u8ba4\u503c<\/h4>\n\n\n\n
    \u4f7f\u7528 SET DEFAULT<\/code> \u53ef\u4ee5\u4e3a\u5217\u8bbe\u7f6e\u4e00\u4e2a\u9ed8\u8ba4\u503c\u3002<\/p>\n\n\n\n
    ALTER TABLE employees ALTER COLUMN emp_age SET DEFAULT 30;<\/code><\/pre>\n\n\n\n
    \u8fd9\u4f1a\u5c06 emp_age<\/code> \u5217\u7684\u9ed8\u8ba4\u503c\u8bbe\u7f6e\u4e3a 30<\/code>\u3002<\/p>\n\n\n\n
    \u5982\u679c\u60f3\u8981\u5220\u9664\u9ed8\u8ba4\u503c\uff0c\u4f7f\u7528\uff1a<\/p>\n\n\n\n
    ALTER TABLE employees ALTER COLUMN emp_age DROP DEFAULT;<\/code><\/pre>\n\n\n\n
    2.5 \u4fee\u6539\u5217\u7684\u7ea6\u675f<\/h4>\n\n\n\n
    \u5982\u679c\u60f3\u4fee\u6539\u5217\u7684\u7ea6\u675f\uff0c\u6bd4\u5982\u5c06\u5217\u6539\u4e3a NOT NULL<\/code> \u6216\u8005 UNIQUE<\/code>\uff0c\u53ef\u4ee5\u4f7f\u7528 MODIFY<\/code> \u6216 ALTER<\/code>\u3002<\/p>\n\n\n\n
    ALTER TABLE employees MODIFY COLUMN emp_email VARCHAR(255) NOT NULL;<\/code><\/pre>\n\n\n\n
    \u8fd9\u4f1a\u5c06 emp_email<\/code> \u5217\u8bbe\u7f6e\u4e3a NOT NULL<\/code>\uff0c\u610f\u5473\u7740\u8be5\u5217\u4e0d\u5141\u8bb8\u4e3a\u7a7a\u3002<\/p>\n\n\n\n
    2.6 \u4fee\u6539\u8868\u540d<\/h4>\n\n\n\n
    \u4f7f\u7528 RENAME TO<\/code> \u8bed\u6cd5\u53ef\u4ee5\u4fee\u6539\u8868\u540d\u3002<\/p>\n\n\n\n
    ALTER TABLE employees RENAME TO staff;<\/code><\/pre>\n\n\n\n
    \u6b64\u547d\u4ee4\u5c06 employees<\/code> \u8868\u91cd\u547d\u540d\u4e3a staff<\/code>\u3002<\/p>\n\n\n\n
    2.7 \u4fee\u6539\u8868\u7684\u5b58\u50a8\u5f15\u64ce<\/h4>\n\n\n\n
    \u4f60\u53ef\u4ee5\u4fee\u6539\u8868\u7684\u5b58\u50a8\u5f15\u64ce\u3002\u4f8b\u5982\uff0c\u5c06\u4e00\u4e2a\u8868\u4ece MyISAM<\/code> \u4fee\u6539\u4e3a InnoDB<\/code>\uff1a<\/p>\n\n\n\n
    ALTER TABLE employees ENGINE = InnoDB;<\/code><\/pre>\n\n\n\n
    3. ALTER \u8868\u7684\u8fdb\u9636\u64cd\u4f5c<\/strong><\/h3>\n\n\n\n
    3.1 \u6dfb\u52a0\u7d22\u5f15<\/h4>\n\n\n\n
    \u4f60\u53ef\u4ee5\u4e3a\u8868\u6dfb\u52a0\u7d22\u5f15\uff08\u5305\u62ec\u552f\u4e00\u7d22\u5f15\uff09\u6765\u63d0\u9ad8\u67e5\u8be2\u6027\u80fd\u3002<\/p>\n\n\n\n
    ALTER TABLE employees ADD INDEX idx_emp_name (emp_name);<\/code><\/pre>\n\n\n\n
    \u8fd9\u4f1a\u4e3a emp_name<\/code> \u5217\u521b\u5efa\u4e00\u4e2a\u666e\u901a\u7d22\u5f15\u3002<\/p>\n\n\n\n
    \u5982\u679c\u4f60\u60f3\u521b\u5efa\u552f\u4e00\u7d22\u5f15\uff0c\u4f7f\u7528 UNIQUE<\/code>\uff1a<\/p>\n\n\n\n
    ALTER TABLE employees ADD UNIQUE idx_emp_email (emp_email);<\/code><\/pre>\n\n\n\n
    \u8fd9\u4f1a\u4e3a emp_email<\/code> \u5217\u521b\u5efa\u4e00\u4e2a\u552f\u4e00\u7d22\u5f15\u3002<\/p>\n\n\n\n
    3.2 \u5220\u9664\u7d22\u5f15<\/h4>\n\n\n\n
    \u5982\u679c\u4f60\u4e0d\u518d\u9700\u8981\u67d0\u4e2a\u7d22\u5f15\uff0c\u53ef\u4ee5\u4f7f\u7528 DROP INDEX<\/code> \u5220\u9664\u5b83\uff1a<\/p>\n\n\n\n
    ALTER TABLE employees DROP INDEX idx_emp_name;<\/code><\/pre>\n\n\n\n
    \u8fd9\u4f1a\u5220\u9664 idx_emp_name<\/code> \u7d22\u5f15\u3002<\/p>\n\n\n\n
    3.3 \u4fee\u6539\u8868\u7684\u5b57\u7b26\u96c6\u548c\u6392\u5e8f\u89c4\u5219<\/h4>\n\n\n\n
    \u5982\u679c\u4f60\u9700\u8981\u4fee\u6539\u8868\u7684\u5b57\u7b26\u96c6\u6216\u8005\u6392\u5e8f\u89c4\u5219\uff08\u6bd4\u5982\u4ece latin1<\/code> \u8f6c\u6362\u4e3a utf8<\/code>\uff09\uff0c\u53ef\u4ee5\u4f7f\u7528 CHARACTER SET<\/code> \u548c COLLATE<\/code>\u3002<\/p>\n\n\n\n
    ALTER TABLE employees CHARACTER SET utf8 COLLATE utf8_general_ci;<\/code><\/pre>\n\n\n\n
    \u8fd9\u4f1a\u5c06\u8868\u7684\u5b57\u7b26\u96c6\u6539\u4e3a utf8<\/code>\uff0c\u5e76\u8bbe\u7f6e\u6392\u5e8f\u89c4\u5219\u4e3a utf8_general_ci<\/code>\u3002<\/p>\n\n\n\n
    3.4 \u4fee\u6539\u8868\u7684 AUTO_INCREMENT \u503c<\/h4>\n\n\n\n
    AUTO_INCREMENT<\/code> \u7528\u4e8e\u81ea\u52a8\u751f\u6210\u552f\u4e00\u7684\u6570\u5b57\uff08\u901a\u5e38\u7528\u4e8e\u4e3b\u952e\uff09\u3002\u53ef\u4ee5\u901a\u8fc7 ALTER TABLE<\/code> \u4fee\u6539 AUTO_INCREMENT<\/code> \u7684\u521d\u59cb\u503c\u3002<\/p>\n\n\n\n
    ALTER TABLE employees AUTO_INCREMENT = 1001;<\/code><\/pre>\n\n\n\n
    \u8fd9\u5c06\u628a employees<\/code> \u8868\u7684 AUTO_INCREMENT<\/code> \u503c\u8bbe\u7f6e\u4e3a 1001<\/code>\uff0c\u610f\u5473\u7740\u4e0b\u4e00\u6761\u63d2\u5165\u7684\u8bb0\u5f55\u5c06\u4ece 1001<\/code> \u5f00\u59cb\u3002<\/p>\n\n\n\n
    3.5 \u4fee\u6539\u5217\u7684\u4f4d\u7f6e<\/h4>\n\n\n\n
    \u53ef\u4ee5\u4f7f\u7528 FIRST<\/code> \u6216 AFTER<\/code> \u6765\u6539\u53d8\u5217\u7684\u4f4d\u7f6e\uff1a<\/p>\n\n\n\n
    ALTER TABLE employees ADD COLUMN emp_department VARCHAR(100) FIRST;<\/code><\/pre>\n\n\n\n
    \u8fd9\u4f1a\u5c06 emp_department<\/code> \u5217\u6dfb\u52a0\u4e3a\u8868\u7684\u7b2c\u4e00\u4e2a\u5217\u3002<\/p>\n\n\n\n
    ALTER TABLE employees ADD COLUMN emp_salary DECIMAL(10, 2) AFTER emp_age;<\/code><\/pre>\n\n\n\n
    \u8fd9\u4f1a\u5c06 emp_salary<\/code> \u5217\u6dfb\u52a0\u5230 emp_age<\/code> \u5217\u4e4b\u540e\u3002<\/p>\n\n\n\n
    3.6 \u4fee\u6539\u8868\u7684\u7ea6\u675f<\/h4>\n\n\n\n
    MySQL \u5141\u8bb8\u4f60\u5728\u8868\u4e0a\u6dfb\u52a0\u6216\u5220\u9664\u7ea6\u675f\u3002\u4f60\u53ef\u4ee5\u6dfb\u52a0\u4e3b\u952e\u7ea6\u675f\u3001\u5916\u952e\u7ea6\u675f\u3001\u68c0\u67e5\u7ea6\u675f\u7b49\u3002<\/p>\n\n\n\n
    \u6dfb\u52a0\u4e3b\u952e\u7ea6\u675f\uff1a<\/strong><\/p>\n\n\n\n
    ALTER TABLE employees ADD PRIMARY KEY (emp_id);<\/code><\/pre>\n\n\n\n
    \u5220\u9664\u4e3b\u952e\u7ea6\u675f\uff1a<\/strong><\/p>\n\n\n\n
    ALTER TABLE employees DROP PRIMARY KEY;<\/code><\/pre>\n\n\n\n
    \u6dfb\u52a0\u5916\u952e\u7ea6\u675f\uff1a<\/strong><\/p>\n\n\n\n
    ALTER TABLE employees ADD CONSTRAINT fk_dept FOREIGN KEY (dept_id) REFERENCES departments(dept_id);<\/code><\/pre>\n\n\n\n
    \u5220\u9664\u5916\u952e\u7ea6\u675f\uff1a<\/strong><\/p>\n\n\n\n
    ALTER TABLE employees DROP FOREIGN KEY fk_dept;<\/code><\/pre>\n\n\n\n
    4. \u6ce8\u610f\u4e8b\u9879<\/strong><\/h3>\n\n\n\n
      \n
    • \u6570\u636e\u7c7b\u578b\u7684\u53d8\u5316<\/strong>\uff1a\u5728\u4fee\u6539\u5217\u7684\u6570\u636e\u7c7b\u578b\u65f6\uff0cMySQL \u4f1a\u68c0\u67e5\u6570\u636e\u7684\u517c\u5bb9\u6027\u3002\u5982\u679c\u65b0\u7684\u6570\u636e\u7c7b\u578b\u4e0d\u517c\u5bb9\u73b0\u6709\u6570\u636e\uff0c\u53ef\u80fd\u4f1a\u5bfc\u81f4\u9519\u8bef\u6216\u8005\u6570\u636e\u4e22\u5931\u3002<\/li>\n\n\n\n
    • \u7d22\u5f15<\/strong>\uff1a\u5728\u8fdb\u884c\u67d0\u4e9b\u64cd\u4f5c\u65f6\uff08\u5982\u5220\u9664\u5217\uff09\uff0c\u5982\u679c\u8be5\u5217\u6709\u7d22\u5f15\uff0cMySQL \u4f1a\u81ea\u52a8\u5220\u9664\u76f8\u5173\u7d22\u5f15\u3002<\/li>\n\n\n\n
    • \u6027\u80fd\u5f71\u54cd<\/strong>\uff1aALTER<\/code> \u64cd\u4f5c\u53ef\u80fd\u4f1a\u5bfc\u81f4\u8868\u9501\u5b9a\uff0c\u5c24\u5176\u662f\u5728\u5927\u578b\u8868\u4e0a\u6267\u884c\u65f6\u3002\u56e0\u6b64\uff0c\u5728\u9ad8\u5e76\u53d1\u7684\u73af\u5883\u4e0b\uff0c\u6700\u597d\u5728\u975e\u9ad8\u5cf0\u65f6\u6bb5\u8fdb\u884c\u8fd9\u4e9b\u64cd\u4f5c\u3002<\/li>\n\n\n\n
    • \u5907\u4efd<\/strong>\uff1a\u5728\u8fdb\u884c\u4efb\u4f55\u7ed3\u6784\u6027\u53d8\u66f4\u65f6\uff0c\u5efa\u8bae\u5148\u8fdb\u884c\u6570\u636e\u5907\u4efd\uff0c\u4ee5\u9632\u64cd\u4f5c\u51fa\u73b0\u610f\u5916\u3002<\/li>\n<\/ul>\n\n\n\n
      5. \u603b\u7ed3<\/strong><\/h3>\n\n\n\n
        \n
      • ALTER<\/code> \u547d\u4ee4\u662f\u4fee\u6539\u6570\u636e\u5e93\u8868\u7ed3\u6784\u7684\u5f3a\u5927\u5de5\u5177\uff0c\u80fd\u591f\u5e2e\u52a9\u4f60\u6dfb\u52a0\u3001\u5220\u9664\u5217\uff0c\u4fee\u6539\u6570\u636e\u7c7b\u578b\uff0c\u6dfb\u52a0\u7d22\u5f15\uff0c\u4fee\u6539\u7ea6\u675f\u7b49\u3002<\/li>\n\n\n\n
      • \u5e38\u89c1\u7684\u64cd\u4f5c\u5305\u62ec ADD COLUMN<\/code>\u3001DROP COLUMN<\/code>\u3001MODIFY COLUMN<\/code>\u3001RENAME TO<\/code>\u3001CHANGE COLUMN<\/code> \u7b49\u3002<\/li>\n\n\n\n
      • \u8fdb\u884c\u7ed3\u6784\u4fee\u6539\u65f6\u8981\u8c28\u614e\uff0c\u5c24\u5176\u662f\u5728\u751f\u4ea7\u73af\u5883\u4e2d\uff0c\u786e\u4fdd\u6570\u636e\u5b8c\u6574\u6027\uff0c\u5e76\u8003\u8651\u5bf9\u7cfb\u7edf\u6027\u80fd\u7684\u5f71\u54cd\u3002<\/li>\n<\/ul>\n\n\n\n
        \u901a\u8fc7\u719f\u7ec3\u638c\u63e1 ALTER<\/code> \u547d\u4ee4\uff0c\u4f60\u5c06\u80fd\u591f\u7075\u6d3b\u5730\u5bf9\u6570\u636e\u5e93\u7ed3\u6784\u8fdb\u884c\u4fee\u6539\u548c\u4f18\u5316\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
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