{"id":1551,"date":"2022-11-11T21:49:57","date_gmt":"2022-11-11T13:49:57","guid":{"rendered":"https:\/\/qaqaq.top\/?p=1551"},"modified":"2022-11-27T12:40:58","modified_gmt":"2022-11-27T04:40:58","slug":"%e6%95%b0%e6%8d%ae%e5%ae%8c%e6%95%b4%e6%80%a7%e4%b8%8e%e7%ba%a6%e6%9d%9f%e7%9a%84%e5%88%86%e7%b1%bb%e3%80%81%e9%9d%9e%e7%a9%ba%e7%ba%a6%e6%9d%9f%e7%9a%84%e4%bd%bf%e7%94%a8%e3%80%81%e5%94%af%e4%b8%80","status":"publish","type":"post","link":"https:\/\/qaqaq.top\/?p=1551","title":{"rendered":"\u6570\u636e\u5b8c\u6574\u6027\u4e0e\u7ea6\u675f\u7684\u5206\u7c7b\u3001\u975e\u7a7a\u7ea6\u675f\u7684\u4f7f\u7528\u3001\u552f\u4e00\u6027\u7ea6\u675f\u7684\u4f7f\u7528\u3001\u4e3b\u952e\u7ea6\u675f\u7684\u4f7f\u7528\u3001AUTO_INCREMENT\u3001\u5916\u952e\u7ea6\u675f\u7684\u4f7f\u7528\u3001\u68c0\u67e5\u7ea6\u675f\u4e0e\u9ed8\u8ba4\u503c\u7ea6\u675f"},"content":{"rendered":"\n<pre class=\"wp-block-code\"><code># \u7b2c13\u7ae0_\u7ea6\u675f\r\n\r\n\/*\r\n 1. \u57fa\u7840\u77e5\u8bc6\r\n 1.1 \u4e3a\u4ec0\u4e48\u9700\u8981\u7ea6\u675f\uff1f \u4e3a\u4e86\u4fdd\u8bc1\u6570\u636e\u7684\u5b8c\u6574\u6027\uff01\r\n\r\n 1.2 \u4ec0\u4e48\u53eb\u7ea6\u675f\uff1f\u5bf9\u8868\u4e2d\u5b57\u6bb5\u7684\u9650\u5236\u3002\r\n\r\n 1.3 \u7ea6\u675f\u7684\u5206\u7c7b\uff1a\r\n\r\n \u89d2\u5ea61\uff1a\u7ea6\u675f\u7684\u5b57\u6bb5\u7684\u4e2a\u6570\r\n \u5355\u5217\u7ea6\u675f vs \u591a\u5217\u7ea6\u675f\r\n\r\n \u89d2\u5ea62\uff1a\u7ea6\u675f\u7684\u4f5c\u7528\u8303\u56f4\r\n\r\n \u5217\u7ea7\u7ea6\u675f\uff1a\u5c06\u6b64\u7ea6\u675f\u58f0\u660e\u5728\u5bf9\u5e94\u5b57\u6bb5\u7684\u540e\u9762\r\n \u8868\u7ea7\u7ea6\u675f\uff1a\u5728\u8868\u4e2d\u6240\u6709\u5b57\u6bb5\u90fd\u751f\u58f0\u660e\u5b8c\uff0c\u5728\u6240\u6709\u5b57\u6bb5\u7684\u540e\u9762\u58f0\u660e\u7684\u7ea6\u675f\r\n\r\n \u89d2\u5ea63\uff1a\u7ea6\u675f\u7684\u4f5c\u7528\uff08\u6216\u529f\u80fd\uff09\uff1a\r\n\r\n \u2460 NOT NULL\uff08\u975e\u7a7a\u7ea6\u675f\uff09\r\n \u2461 UNIQUE\uff08\u552f\u4e00\u6027\u7ea6\u675f\uff09\r\n \u2462 PRIMARY KEY\uff08\u4e3b\u952e\u7ea6\u675f\uff09\r\n \u2463 FOREIGN KEY\uff08\u5916\u952e\u7ea6\u675f\uff09\r\n \u2464 CHECK\uff08\u68c0\u67e5\u7ea6\u675f\uff09\r\n \u2465 DEFAULT\uff08\u9ed8\u8ba4\u503c\u7ea6\u675f\uff09\r\n\r\n 1.4 \u5982\u4f55\u6dfb\u52a0\u7ea6\u675f\uff1f\r\n\r\n CREATE TABLE \u65f6\u6dfb\u52a0\u7ea6\u675f\r\n\r\n ALTER TABLE \u65f6\u589e\u52a0\u7ea6\u675f\u3001\u5220\u9664\u7ea6\u675f\r\n\r\n *\/\r\n\r\n# 2. \u5982\u4f55\u67e5\u770b\u8868\u4e2d\u7684\u7ea6\u675f\r\nSELECT * FROM information_schema.table_constraints\r\nWHERE table_name = 'test1';\r\n\r\nCREATE DATABASE dbtest13;\r\n\r\nUSE dbtest13;\r\n\r\n# 3. NOT NULL\uff08\u975e\u7a7a\u7ea6\u675f\uff09\r\n# 3.1 \u5728CREATE TABLE\u65f6\u6dfb\u52a0\u7ea6\u675f\r\n\r\nCREATE TABLE test1(\r\n    id INT NOT NULL,\r\n    last_name VARCHAR(15) NOT NULL,\r\n    email VARCHAR(25),\r\n    salary DECIMAL(10,2)\r\n);\r\n\r\nDESC test1;\r\n\r\nINSERT INTO test1(id, last_name, email, salary)\r\nVALUES(1,'Tom','tom@126.com',3400);\r\n\r\n# \u9519\u8bef\uff1aColumn 'last_name' cannot be null\r\nINSERT INTO test1(id, last_name, email, salary)\r\nVALUES(2,NULL,'tom1@126.com',3400);\r\n\r\nINSERT INTO test1(id, last_name, email, salary)\r\nVALUES(NULL,'Jerry','jerry@126.com',3400);\r\n\r\nINSERT INTO test1(id,email)\r\nVALUES(2,'abc@126.com');\r\n\r\nUPDATE test1\r\nSET last_name = NULL\r\nWHERE id = 1;\r\n\r\nUPDATE test1\r\nSET email = 'tom@126.com'\r\nWHERE id = 1;\r\n\r\n# 3.2 \u5728ALTER TABLE\u65f6\u6dfb\u52a0\u7ea6\u675f\r\nSELECT * FROM test1;\r\n\r\nDESC test1;\r\n\r\nALTER TABLE test1\r\nMODIFY email VARCHAR(25) NOT NULL;\r\n\r\n# 3.3 \u5728ALTER TABLE\u65f6\u5220\u9664\u7ea6\u675f\r\nALTER TABLE test1\r\nMODIFY email VARCHAR(25) NULL;\r\n\r\n# 4. UNIQUE \uff08\u552f\u4e00\u6027\u7ea6\u675f\uff09\r\n\r\n# 4.1 \u5728CREATE TABLE\u65f6\u6dfb\u52a0\u7ea6\u675f\r\nCREATE TABLE test2(\r\n    id INT UNIQUE,  #\u5217\u7ea7\u7ea6\u675f\r\n    lastname VARCHAR(15),\r\n    email VARCHAR(25),\r\n    salary DECIMAL(10,2),\r\n\r\n    # \u8868\u7ea7\u7ea6\u675f\r\n    CONSTRAINT uk_test2_email UNIQUE(email)\r\n);\r\n\r\nDESC test2;\r\n\r\nSELECT * FROM information_schema.table_constraints\r\nWHERE table_name = 'test2';\r\n\r\n# \u5728\u521b\u5efa\u552f\u4e00\u7ea6\u675f\u7684\u65f6\u5019\uff0c\u5982\u679c\u4e0d\u7ed9\u552f\u4e00\u7ea6\u675f\u547d\u540d\uff0c\u5c31\u9ed8\u8ba4\u548c\u5217\u540d\u76f8\u540c\u3002\r\n\r\nINSERT INTO test2(id, lastname, email, salary)\r\nVALUES(1,'Tom','tom@126.com',4500);\r\n\r\n# \u9519\u8bef\uff1aDuplicate entry '1' for key 'test2.id'\r\nINSERT INTO test2(id, lastname, email, salary)\r\nVALUES(1,'Tom1','tom1@126.com',4600);\r\n\r\n# \u9519\u8bef\uff1aDuplicate entry 'tom@126.com' for key 'test2.uk_test2_email'\r\nINSERT INTO test2(id, lastname, email, salary)\r\nVALUES(2,'Tom1','tom@126.com',4600);\r\n\r\n# \u53ef\u4ee5\u5411\u58f0\u660e\u4e3aunique\u7684\u5b57\u6bb5\u4e0a\u6dfb\u52a0null\u503c\u3002\u800c\u4e14\u53ef\u4ee5\u591a\u6b21\u6dfb\u52a0null\r\nINSERT INTO test2(id, lastname, email, salary)\r\nVALUES(2,'Tom1',NULL,4600);\r\n\r\nINSERT INTO test2(id, lastname, email, salary)\r\nVALUES(3,'Tom2',NULL,4600);\r\n\r\nSELECT * FROM test2;\r\n\r\n# 4.2 \u5728ALTER TABLE\u65f6\u6dfb\u52a0\u7ea6\u675f\r\n\r\nDESC test2;\r\n\r\nUPDATE test2\r\nSET salary = 5000\r\nWHERE id = 3;\r\n#\u65b9\u5f0f1\uff1a\r\nALTER TABLE test2\r\nADD CONSTRAINT uk_test2_sal UNIQUE(salary);\r\n#\u65b9\u5f0f2\uff1a\r\nALTER TABLE test2\r\nMODIFY lastname VARCHAR(15) UNIQUE;\r\n\r\n# 4.3 \u590d\u5408\u7684\u552f\u4e00\u6027\u7ea6\u675f\r\nCREATE TABLE USER(\r\n    id INT,\r\n    name VARCHAR(15),\r\n    password VARCHAR(25),\r\n\r\n    # \u8868\u7ea7\u7ea6\u675f\r\n    CONSTRAINT uk_user_name_pwd UNIQUE(name,password)\r\n);\r\n\r\nINSERT INTO USER\r\nVALUES(1,'Tom','abc');\r\n# \u53ef\u4ee5\u6210\u529f\u7684\uff1a\r\nINSERT INTO USER\r\nVALUES(1,'Tom1','abc');\r\n\r\nSELECT *\r\nFROM USER;\r\n\r\n#\u6848\u4f8b\uff1a\u590d\u5408\u7684\u552f\u4e00\u6027\u7ea6\u675f\u7ea6\u675f\u7684\u6848\u4f8b\r\n#\u5b66\u751f\u8868\r\ncreate table student(\r\n    sid int, #\u5b66\u53f7\r\n    sname varchar(20),  #\u59d3\u540d\r\n    tel char(11) unique key, #\u7535\u8bdd\r\n    cardid char(18) unique key #\u8eab\u4efd\u8bc1\u53f7\r\n    );\r\n\r\n#\u8bfe\u7a0b\u8868\r\ncreate table course(\r\n    cid int, #\u8bfe\u7a0b\u7f16\u53f7\r\n    cname varchar(20) #\u8bfe\u7a0b\u540d\u79f0\r\n    );\r\n\r\n#\u9009\u8bfe\u8868\r\ncreate table student_course(\r\n    id int,\r\n    sid int,    #\u5b66\u53f7\r\n    cid int,    #\u8bfe\u7a0b\u7f16\u53f7\r\n    score int,\r\n    unique key(sid,cid) #\u590d\u5408\u552f\u4e00\r\n    );\r\n\r\ninsert into student values(1,'\u5f20\u4e09','13710011002','101223199012015623');#\u6210\u529f\r\ninsert into student values(2,'\u674e\u56db','13710011003','101223199012015624');#\u6210\u529f\r\ninsert into course values(1001,'Java'),(1002,'MySQL');#\u6210\u529f\r\n\r\nSELECT * FROM student;\r\n\r\nSELECT * FROM course;\r\n\r\ninsert into student_course values\r\n    (1, 1, 1001, 89),\r\n    (2, 1, 1002, 90),\r\n    (3, 2, 1001, 88),\r\n    (4, 2, 1002, 56);#\u6210\u529f\r\n\r\nSELECT * FROM student_course;\r\n\r\n# \u9519\u8bef\uff1aDuplicate entry '2-1002' for key 'student_course.sid'\r\nINSERT INTO student_course\r\nVALUES(5,2,1002,67);\r\n\r\n# 4.4 \u5220\u9664\u552f\u4e00\u6027\u7ea6\u675f\r\n-- \u6dfb\u52a0\u552f\u4e00\u6027\u7ea6\u675f\u7684\u5217\u4e0a\u4e5f\u4f1a\u81ea\u52a8\u521b\u5efa\u552f\u4e00\u7d22\u5f15\u3002\r\n-- \u5220\u9664\u552f\u4e00\u7ea6\u675f\u53ea\u80fd\u901a\u8fc7\u5220\u9664\u552f\u4e00\u7d22\u5f15\u7684\u65b9\u5f0f\u5220\u9664\u3002\r\n-- \u5220\u9664\u65f6\u9700\u8981\u6307\u5b9a\u552f\u4e00\u7d22\u5f15\u540d\uff0c\u552f\u4e00\u7d22\u5f15\u540d\u5c31\u548c\u552f\u4e00\u7ea6\u675f\u540d\u4e00\u6837\u3002\r\n-- \u5982\u679c\u521b\u5efa\u552f\u4e00\u7ea6\u675f\u65f6\u672a\u6307\u5b9a\u540d\u79f0\uff0c\u5982\u679c\u662f\u5355\u5217\uff0c\u5c31\u9ed8\u8ba4\u548c\u5217\u540d\u76f8\u540c\uff1b\u5982\u679c\u662f\u7ec4\u5408\u5217\uff0c\u90a3\u4e48\u9ed8\u8ba4\u548c()\u4e2d\u6392\u5728\u7b2c\u4e00\u4e2a\u7684\u5217\u540d\u76f8\u540c\u3002\u4e5f\u53ef\u4ee5\u81ea\u5b9a\u4e49\u552f\u4e00\u6027\u7ea6\u675f\u540d\u3002\r\n\r\nSELECT * FROM information_schema.table_constraints\r\nWHERE table_name = 'student_course';\r\n\r\nSELECT * FROM information_schema.table_constraints\r\nWHERE table_name = 'test2';\r\n\r\nDESC test2;\r\n\r\n#\u5982\u4f55\u5220\u9664\u552f\u4e00\u6027\u7d22\u5f15\r\nALTER TABLE test2\r\nDROP INDEX lastname;\r\n\r\nALTER TABLE test2\r\nDROP INDEX uk_test2_sal;\r\n\r\n# 5. PRIMARY KEY\uff08\u4e3b\u952e\u7ea6\u675f\uff09\r\n# 5.1 \u5728CREATE TABLE\u65f6\u6dfb\u52a0\u7ea6\u675f\r\n\r\n#\u4e00\u4e2a\u8868\u4e2d\u6700\u591a\u53ea\u80fd\u6709\u4e00\u4e2a\u4e3b\u952e\u7ea6\u675f\u3002\r\n# \u9519\u8bef\uff1aMultiple primary key defined\r\nCREATE TABLE test3(\r\n    id INT PRIMARY KEY,     #\u5217\u7ea7\u7ea6\u675f\r\n    last_name VARCHAR(15) PRIMARY KEY,\r\n    salary DECIMAL(10,2),\r\n    email VARCHAR(25)\r\n);\r\n\r\n# \u4e3b\u952e\u7ea6\u675f\u7279\u5f81\uff1a\u975e\u7a7a\u4e14\u552f\u4e00\uff0c\u7528\u4e8e\u552f\u4e00\u7684\u6807\u8bc6\u8868\u4e2d\u7684\u4e00\u6761\u8bb0\u5f55\u3002\r\nCREATE TABLE test4(\r\n    id INT PRIMARY KEY,     #\u5217\u7ea7\u7ea6\u675f\r\n    last_name VARCHAR(15),\r\n    salary DECIMAL(10,2),\r\n    email VARCHAR(25)\r\n);\r\n\r\n# MySQL\u7684\u4e3b\u952e\u540d\u603b\u662fPRIMARY\uff0c\u5c31\u7b97\u81ea\u5df1\u547d\u540d\u4e86\u4e3b\u952e\u7ea6\u675f\u540d\u4e5f\u6ca1\u7528\u3002\r\nCREATE TABLE test5(\r\n    id INT,\r\n    last_name VARCHAR(15),\r\n    salary DECIMAL(10,2),\r\n    email VARCHAR(25),\r\n\r\n    #\u8868\u7ea7\u7ea6\u675f\r\n    CONSTRAINT pk_test5_id PRIMARY KEY(id)  #\u6ca1\u6709\u5fc5\u8981\u8d77\u540d\u5b57\u3002\r\n);\r\n\r\nSELECT * FROM information_schema.table_constraints\r\nWHERE table_name = 'test5';\r\n\r\nINSERT INTO test4(id, last_name, salary, email)\r\nVALUES(1,'Tom',4500,'tom@126.com');\r\n\r\n# \u9519\u8bef\uff1aDuplicate entry '1' for key 'test4.PRIMARY'\r\nINSERT INTO test4(id, last_name, salary, email)\r\nVALUES(1,'Tom',4500,'tom@126.com');\r\n\r\n# \u9519\u8bef\uff1aColumn 'id' cannot be null\r\nINSERT INTO test4(id, last_name, salary, email)\r\nVALUES(NULL,'Tom',4500,'tom@126.com');\r\n\r\nSELECT * FROM test4;\r\n\r\nCREATE TABLE user1(\r\n    id INT,\r\n    name VARCHAR(15),\r\n    password VARCHAR(25),\r\n\r\n    PRIMARY KEY(name,password)\r\n);\r\n\r\n# \u5982\u679c\u662f\u591a\u5217\u7ec4\u5408\u7684\u590d\u5408\u4e3b\u952e\u7ea6\u675f\uff0c\u90a3\u4e48\u8fd9\u4e9b\u5217\u90fd\u4e0d\u5141\u8bb8\u4e3a\u7a7a\u503c\uff0c\u5e76\u4e14\u7ec4\u5408\u7684\u503c\u4e0d\u5141\u8bb8\u91cd\u590d\u3002\r\nINSERT INTO user1\r\nVALUES(1,'Tom','abc');\r\n\r\nINSERT INTO user1\r\nVALUES(1,'Tom1','abc');\r\n# \u9519\u8bef\uff1aColumn 'name' cannot be null\r\nINSERT INTO user1\r\nVALUES(1,NULL,'abc');\r\n\r\nSELECT * FROM user1;\r\n\r\n# 5.2 \u5728ALTER TABLE\u65f6\u6dfb\u52a0\u7ea6\u675f\r\n\r\nCREATE TABLE test6(\r\n    id INT,\r\n    last_name VARCHAR(15),\r\n    salary DECIMAL(10,2),\r\n    email VARCHAR(25)\r\n);\r\n\r\nDESC test6;\r\n\r\nALTER TABLE test6\r\nADD PRIMARY KEY (id);\r\n\r\n# 5.3 \u5982\u4f55\u5220\u9664\u4e3b\u952e\u7ea6\u675f\uff08\u5728\u5b9e\u9645\u5f00\u53d1\u4e2d\uff0c\u4e0d\u4f1a\u53bb\u5220\u9664\u8868\u4e2d\u7684\u4e3b\u952e\u7ea6\u675f\uff01\uff09\r\nALTER TABLE test6\r\nDROP PRIMARY KEY;\r\n\r\n# 6. \u81ea\u589e\u957f\u5217\uff1aAUTO_INCREMENT\r\n# 6.1 \u5728CREATE TABLE\u65f6\u6dfb\u52a0\r\nCREATE TABLE test7(\r\n    id INT PRIMARY KEY AUTO_INCREMENT,\r\n    last_name VARCHAR(15)\r\n);\r\n#\u5f00\u53d1\u4e2d\uff0c\u4e00\u65e6\u4e3b\u952e\u4f5c\u7528\u7684\u5b57\u6bb5\u4e0a\u58f0\u660e\u6709AUTO_INCREMENT, \u5219\u6211\u4eec\u5728\u6dfb\u52a0\u6570\u636e\u65f6\uff0c\u5c31\u4e0d\u8981\u7ed9\u4e3b\u952e\r\n#\u5bf9\u5e94\u7684\u5b57\u6bb5\u53bb\u8d4b\u503c\u4e86\u3002\r\nINSERT INTO test7(last_name)\r\nVALUES('Tom');\r\n\r\nSELECT * FROM test7;\r\n\r\n#\u5f53\u6211\u4eec\u5411\u4e3b\u952e\uff08\u542bAUTO_INCREMENT\uff09\u7684\u5b57\u6bb5\u4e0a\u6dfb\u52a00 \u6216 null\u65f6\uff0c\u5b9e\u9645\u4e0a\u4f1a\u81ea\u52a8\u7684\u5f80\u4e0a\u6dfb\u52a0\u6307\u5b9a\u7684\u5b57\u6bb5\u7684\u6570\u503c\u3002\r\nINSERT INTO test7(id,last_name)\r\nVALUES(0,'Tom');\r\n\r\nINSERT INTO test7(id,last_name)\r\nVALUES(NULL,'Tom');\r\n\r\nINSERT INTO test7(id,last_name)\r\nVALUES(10,'Tom')\r\n\r\nINSERT INTO test7(id,last_name)\r\nVALUES(-10,'Tom');\r\n\r\n# 6.2 \u5728ALTER TABLE \u65f6\u6dfb\u52a0\r\nCREATE TABLE test8(\r\n    id INT PRIMARY KEY,\r\n    last_name VARCHAR(15)\r\n);\r\n\r\nDESC test8;\r\n\r\nALTER TABLE test8\r\nMODIFY id INT AUTO_INCREMENT;\r\n\r\n# 6.3 \u5728ALTER TABLE \u65f6\u5220\u9664\r\nALTER TABLE test8\r\nMODIFY id INT;\r\n\r\n# 6.4 MySQL 8.0\u65b0\u7279\u6027\u2014\u81ea\u589e\u53d8\u91cf\u7684\u6301\u4e45\u5316\r\n\r\n#\u5728MySQL 5.7\u4e2d\u6f14\u793a\r\nCREATE TABLE test9(\r\n    id INT PRIMARY KEY AUTO_INCREMENT\r\n);\r\n\r\nINSERT INTO test9\r\nVALUES(0),(0),(0),(0);\r\n\r\nSELECT * FROM test9;\r\n\r\nDELETE FROM test9\r\nWHERE id = 4;\r\n\r\nINSERT INTO test9\r\nVALUES(0);\r\n\r\nDELETE FROM test9\r\nWHERE id = 5;\r\n\r\n#\u91cd\u542f\u670d\u52a1\u5668\r\n\r\nSELECT * FROM test9;\r\n\r\nINSERT INTO test9\r\nVALUES(0);\r\n\r\n#\u5728MySQL 8.0\u4e2d\u6f14\u793a\r\nCREATE TABLE test9(\r\n    id INT PRIMARY KEY AUTO_INCREMENT\r\n);\r\n\r\nINSERT INTO test9\r\nVALUES(0),(0),(0),(0);\r\n\r\nSELECT * FROM test9;\r\n\r\nDELETE FROM test9\r\nWHERE id = 4;\r\n\r\nINSERT INTO test9\r\nVALUES(0);\r\n\r\nDELETE FROM test9\r\nWHERE id = 5;\r\n\r\n#\u91cd\u542f\u670d\u52a1\u5668\r\n\r\nSELECT * FROM test9;\r\n\r\nINSERT INTO test9\r\nVALUES(0);\r\n\r\n# 7. FOREIGN KEY\uff08\u5916\u952e\u7ea6\u675f\uff09\r\n# 7.1 \u5728CREATE TABLE \u65f6\u6dfb\u52a0\r\n\r\n#\u4e3b\u8868\u548c\u4ece\u8868\uff1a\u7236\u8868\u548c\u5b50\u8868\r\n\r\n# \u2460 \u5148\u521b\u5efa\u4e3b\u8868\r\nCREATE TABLE dept1(\r\n    dept_id INT,\r\n    dept_name VARCHAR(15)\r\n);\r\n# \u2461 \u518d\u521b\u5efa\u4ece\u8868\r\nCREATE TABLE emp1(\r\n    emp_id INT PRIMARY KEY AUTO_INCREMENT,\r\n    emp_name VARCHAR(15),\r\n    department_id INT,\r\n\r\n    #\u8868\u7ea7\u7ea6\u675f\r\n    CONSTRAINT fk_emp1_dept_id FOREIGN KEY (department_id) REFERENCES dept1(dept_id)\r\n);\r\n\r\n#\u4e0a\u8ff0\u64cd\u4f5c\u62a5\u9519\uff0c\u56e0\u4e3a\u4e3b\u8868\u4e2d\u7684dept_id\u4e0a\u6ca1\u6709\u4e3b\u952e\u7ea6\u675f\u6216\u552f\u4e00\u6027\u7ea6\u675f\u3002\r\n# \u2460 \u6dfb\u52a0\r\nALTER TABLE dept1\r\nADD PRIMARY KEY (dept_id);\r\n\r\nDESC dept1;\r\n\r\n# \u2463 \u518d\u521b\u5efa\u4ece\u8868\r\nCREATE TABLE emp1(\r\n    emp_id INT PRIMARY KEY AUTO_INCREMENT,\r\n    emp_name VARCHAR(15),\r\n    department_id INT,\r\n\r\n    #\u8868\u7ea7\u7ea6\u675f\r\n    CONSTRAINT fk_emp1_dept_id FOREIGN KEY (department_id) REFERENCES dept1(dept_id)\r\n);\r\n\r\nDESC emp1;\r\n\r\nSELECT * FROM information_schema.table_constraints\r\nWHERE table_name = 'emp1';\r\n\r\n# 7.2 \u6f14\u793a\u5916\u952e\u7684\u6548\u679c\r\n#\u6dfb\u52a0\u5931\u8d25\r\nINSERT INTO emp1\r\nVALUES(1001,'Tom',10);\r\n\r\n#\r\nINSERT INTO dept1\r\nVALUES(10,'IT');\r\n#\u5728\u4e3b\u8868dept1\u4e2d\u6dfb\u52a0\u4e8610\u53f7\u90e8\u95e8\u4ee5\u540e\uff0c\u6211\u4eec\u5c31\u53ef\u4ee5\u5728\u4ece\u8868\u4e2d\u6dfb\u52a010\u53f7\u90e8\u95e8\u7684\u5458\u5de5\r\nINSERT INTO emp1\r\nVALUES(1001,'Tom',10);\r\n\r\n#\u5220\u9664\u5931\u8d25\r\nDELETE FROM dept1\r\nWHERE dept_id = 10;\r\n\r\n#\u66f4\u65b0\u5931\u8d25\r\nUPDATE dept1\r\nSET dept_id = 20\r\nWHERE dept_id = 10;\r\n\r\n# 7.3 \u5728ALTER TABLE\u65f6\u6dfb\u52a0\u5916\u952e\u7ea6\u675f\r\nCREATE TABLE dept2(\r\n    dept_id INT PRIMARY KEY,\r\n    dept_name VARCHAR(15)\r\n);\r\n\r\nCREATE TABLE emp2(\r\n    emp_id INT PRIMARY KEY AUTO_INCREMENT,\r\n    emp_name VARCHAR(15),\r\n    department_id INT\r\n);\r\n\r\nALTER TABLE emp2\r\nADD CONSTRAINT fk_emp2_dept_id FOREIGN KEY(department_id) REFERENCES dept2(dept_id);\r\n\r\nSELECT * FROM information_schema.table_constraints\r\nWHERE table_name = 'emp2';\r\n\r\n# 7.4 ### \u7ea6\u675f\u7b49\u7ea7\r\n\r\n-- Cascade\u65b9\u5f0f \uff1a\u5728\u7236\u8868\u4e0aupdate\/delete\u8bb0\u5f55\u65f6\uff0c\u540c\u6b65update\/delete\u6389\u5b50\u8868\u7684\u5339\u914d\u8bb0\u5f55\r\n\r\n-- Set null\u65b9\u5f0f \uff1a\u5728\u7236\u8868\u4e0aupdate\/delete\u8bb0\u5f55\u65f6\uff0c\u5c06\u5b50\u8868\u4e0a\u5339\u914d\u8bb0\u5f55\u7684\u5217\u8bbe\u4e3anull\uff0c\u4f46\u662f\u8981\u6ce8\u610f\u5b50\u8868\u7684\u5916\u952e\u5217\u4e0d\u80fd\u4e3anot null\r\n\r\n-- No action\u65b9\u5f0f \uff1a\u5982\u679c\u5b50\u8868\u4e2d\u6709\u5339\u914d\u7684\u8bb0\u5f55\uff0c\u5219\u4e0d\u5141\u8bb8\u5bf9\u7236\u8868\u5bf9\u5e94\u5019\u9009\u952e\u8fdb\u884cupdate\/delete\u64cd\u4f5c\r\n\r\n-- Restrict\u65b9\u5f0f \uff1a\u540cno action\uff0c \u90fd\u662f\u7acb\u5373\u68c0\u67e5\u5916\u952e\u7ea6\u675f\r\n\r\n-- Set default\u65b9\u5f0f \uff08\u5728\u53ef\u89c6\u5316\u5de5\u5177SQLyog\u4e2d\u53ef\u80fd\u663e\u793a\u7a7a\u767d\uff09\uff1a\u7236\u8868\u6709\u53d8\u66f4\u65f6\uff0c\u5b50\u8868\u5c06\u5916\u952e\u5217\u8bbe\u7f6e\u6210\u4e00\u4e2a\u9ed8\u8ba4\u7684\u503c\uff0c\u4f46Innodb\u4e0d\u80fd\u8bc6\u522b\r\n\r\n# \u6f14\u793a\uff1a\r\n# on update cascade on delete set null\r\ncreate table dept(\r\n    did int primary key,\r\n    dname varchar(50)\r\n);\r\n\r\ncreate table emp(\r\n    eid int primary key, #\u5458\u5de5\u7f16\u53f7\r\n    ename varchar(5), #\u5458\u5de5\u59d3\u540d\r\n    deptid int,\r\n    foreign key (deptid) references dept(did) on update cascade on delete set null\r\n#\u628a\u4fee\u6539\u64cd\u4f5c\u8bbe\u7f6e\u4e3a\u7ea7\u8054\u4fee\u6539\u7b49\u7ea7\uff0c\u628a\u5220\u9664\u64cd\u4f5c\u8bbe\u7f6e\u4e3aset null\u7b49\u7ea7);\u3001\r\n);\r\n\r\ninsert into dept values(1001,'\u6559\u5b66\u90e8');\r\ninsert into dept values(1002, '\u8d22\u52a1\u90e8');\r\ninsert into dept values(1003, '\u54a8\u8be2\u90e8');\r\n\r\ninsert into emp values(1,'\u5f20\u4e09',1001); #\u5728\u6dfb\u52a0\u8fd9\u6761\u8bb0\u5f55\u65f6\uff0c\u8981\u6c42\u90e8\u95e8\u8868\u67091001\u90e8\u95e8\r\ninsert into emp values(2,'\u674e\u56db',1001);\r\ninsert into emp values(3,'\u738b\u4e94',1002);\r\n\r\nUPDATE dept\r\nSET did = 1004\r\nWHERE did = 1002;\r\n\r\nDELETE FROM dept\r\nWHERE did = 1004;\r\n\r\n\r\nSELECT *FROM dept;\r\n\r\nSELECT *FROM emp;\r\n\r\n# \u7ed3\u8bba \u5bf9\u4e8e\u5916\u952e\u7ea6\u675f\uff0c\u6700\u597d\u662f\u91c7\u7528: ON UPDATE CASCADE ON DELETE RESTRICT \u7684\u65b9\u5f0f\u3002\r\n\r\n# 7.5 \u5220\u9664\u5916\u952e\u7ea6\u675f\r\n\r\n# \u4e00\u4e2a\u8868\u4e2d\u53ef\u4ee5\u58f0\u660e\u6709\u591a\u4e2a\u5916\u952e\u7ea6\u675f\r\nUSE dbtest13;\r\n\r\nSELECT * FROM information_schema.table_constraints\r\nWHERE table_name = 'emp1';\r\n\r\n#\u5220\u9664\u5916\u952e\u7ea6\u675f\r\n\r\nALTER TABLE emp1\r\nDROP FOREIGN KEY fk_emp1_dept_id;\r\n\r\n#\u518d\u624b\u52a8\u7684\u5220\u9664\u5916\u952e\u7ea6\u675f\u5bf9\u5e94\u7684\u666e\u901a\u7d22\u5f15\r\nSHOW INDEX FROM emp1;\r\n\r\nALTER TABLE emp1\r\nDROP INDEX fk_emp1_dept_id;\r\n\r\n# 8. CHECK \u7ea6\u675f\r\n# MySQL5.7 \u4e0d\u652f\u6301CHECK\u7ea6\u675f\uff0cMySQL8.0\u652f\u6301CHECK\u7ea6\u675f\u3002\r\nCREATE TABLE test10(\r\n    id INT,\r\n    last_name VARCHAR(15),\r\n    salary DECIMAL(10,2) CHECK ( salary > 2000 )\r\n);\r\n\r\nINSERT INTO test10\r\nVALUES(1,'Tom',2500);\r\n\r\n#\u6dfb\u52a0\u5931\u8d25\r\nINSERT INTO test10\r\nVALUES(2,'Tom1',1500);\r\n\r\nSELECT * FROM test10;\r\n\r\n# 9. DEFAULT\u7ea6\u675f\r\n# 9.1 \u5728CREATE TABLE \u6dfb\u52a0\u7ea6\u675f\r\nCREATE TABLE test11(\r\n    id INT,\r\n    last_name VARCHAR(15),\r\n    salary DECIMAL(10,2) DEFAULT 2000\r\n);\r\n\r\nDESC TEST11;\r\n\r\nINSERT INTO test11(id, last_name, salary)\r\nVALUES(1,'Tom',3000);\r\n\r\nINSERT INTO test11(ID, LAST_NAME)\r\nVALUES(2,'Tom');\r\n\r\nSELECT *\r\nFROM TEST11;\r\n\r\n# 9.2 \u5728ALTER TABLE \u6dfb\u52a0\u7ea6\u675f\r\nCREATE TABLE test12(\r\n    id INT,\r\n    last_name VARCHAR(15),\r\n    salary DECIMAL(10,2)\r\n);\r\n\r\nDESC test12;\r\n\r\nALTER TABLE test12\r\nMODIFY salary DECIMAL(8,2) DEFAULT 2500;\r\n\r\n# 9.3 \u5728ALTER TABLE\u5220\u9664\u7ea6\u675f\r\nALTER TABLE test12\r\nMODIFY salary DECIMAL(8,2);\r\n\r\nSHOW CREATE TABLE test12;<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[47],"class_list":["post-1551","post","type-post","status-publish","format-standard","hentry","category-mysql-code","tag-mysql"],"_links":{"self":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1551"}],"collection":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1551"}],"version-history":[{"count":1,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1551\/revisions"}],"predecessor-version":[{"id":1552,"href":"https:\/\/qaqaq.top\/index.php?rest_route=\/wp\/v2\/posts\/1551\/revisions\/1552"}],"wp:attachment":[{"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1551"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1551"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/qaqaq.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1551"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}