MYSQL数据库-修改和删除

删除数据库:

　　$ DROP DATABASE t_name;

重命名一张表：

　　$ RENAME TABLE ori_name TO new_name;

　　$ ALTER TABLE ori_name RENAME new_name;

　　$ ALTER TABLE or_name RENAME TO new_name;

删除一张表：

　　$ DROP TABLE t_name;

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对表结构的修改：

增加表中一列：

　　$ ALTER TABLE t_name ADD COLUMN col_name data_type constrain;

or   $ ALTER TABLE t_name ADD col_name data_type constrain;

规定新加列的位置，放在col_name列的下一列，在SQL语句后加：

　　$ AFTER col_name;

如果想放在第一列,在SQL后加：

　　$ FIRST

删除一列：

　　$ ALTER TABLE t_name DROP COLUMN col_name;

or   $ ALTER TABLE t_name DROP col_name;

列的重命名：

　　$ ALTER TABLE t_name CHANGE ori_col new_col data_type constrain;

改变数据类型：

　　$ ALTER TABLE t_name MODIFY col_name new_data_type;

===================================================

对表内容修改：

修改表中某个值：

　　$ UPDATE t_name SET col1=v1,col2=v2 WHERE condition;

删除一行记录：

　　$ DELETE FROM t_name WHERE condition;

SQL

 CREATE DATABASE test_01;
 
 CREATE DATABASE mysql_shiyan;
 
 use mysql_shiyan;
 
 CREATE TABLE department
 (
   dpt_name   CHAR(20) NOT NULL,
   people_num INT(10) DEFAULT '',
   CONSTRAINT dpt_pk PRIMARY KEY (dpt_name)
  );
 
 CREATE TABLE employee
 (
   id      INT(10) PRIMARY KEY,
   name    CHAR(20),
   age     INT(10),
   salary  INT(10) NOT NULL,
   phone   INT(12) NOT NULL,
   in_dpt  CHAR(20) NOT NULL,
   UNIQUE  (phone),
   CONSTRAINT emp_fk FOREIGN KEY (in_dpt) REFERENCES department(dpt_name)
  );
 
 CREATE TABLE project
 (
   proj_num   INT(10) NOT NULL,
   proj_name  CHAR(20) NOT NULL,
   start_date DATE NOT NULL,
   end_date   DATE DEFAULT '2015-04-01',
   of_dpt     CHAR(20) REFERENCES department(dpt_name),
   CONSTRAINT proj_pk PRIMARY KEY (proj_num,proj_name)
  );
 
 CREATE TABLE table_1
 (
 l_1 INT(10) PRIMARY KEY,
 l_2 INT(10),
 l_3 INT(10)
  );
 
 #INSERT INTO department(dpt_name,people_num) VALUES('\u90e8\u95e8',\u4eba\u6570);
 
 INSERT INTO department(dpt_name,people_num) VALUES('dpt1',11);
 INSERT INTO department(dpt_name,people_num) VALUES('dpt2',12);
 INSERT INTO department(dpt_name,people_num) VALUES('dpt3',10);
 INSERT INTO department(dpt_name,people_num) VALUES('dpt4',15);
 
 #INSERT INTO employee(id,name,age,salary,phone,in_dpt) VALUES(\u7f16\u53f7,'\u540d\u5b57',\u5e74\u9f84,\u5de5\u8d44,\u7535\u8bdd,'\u90e8\u95e8');
 
 INSERT INTO employee(id,name,age,salary,phone,in_dpt) VALUES(01,'Tom',26,2500,119119,'dpt4');
 INSERT INTO employee(id,name,age,salary,phone,in_dpt) VALUES(02,'Jack',24,2500,120120,'dpt2');
 INSERT INTO employee(id,name,age,salary,phone,in_dpt) VALUES(03,'Rose',22,2800,114114,'dpt3');
 INSERT INTO employee(id,name,age,salary,phone,in_dpt) VALUES(04,'Jim',35,3000,100861,'dpt1');
 INSERT INTO employee(id,name,age,salary,phone,in_dpt) VALUES(05,'Mary',21,3000,100101,'dpt2');
 INSERT INTO employee(id,name,age,salary,phone,in_dpt) VALUES(06,'Alex',26,3000,123456,'dpt1');
 
 #INSERT INTO project(proj_num,proj_name,start_date,end_date,of_dpt) VALUES(\u7f16\u53f7,'\u5de5\u7a0b\u540d','\u5f00\u59cb\u65f6\u95f4','\u7ed3\u675f\u65f6\u95f4','\u90e8\u95e8\u540d');
 
 INSERT INTO project(proj_num,proj_name,start_date,end_date,of_dpt) VALUES(01,'proj_a','2015-01-15','2015-01-31','dpt2');
 INSERT INTO project(proj_num,proj_name,start_date,end_date,of_dpt) VALUES(02,'proj_b','2015-01-15','2015-02-15','dpt1');
 INSERT INTO project(proj_num,proj_name,start_date,end_date,of_dpt) VALUES(03,'proj_c','2015-02-01','2015-03-01','dpt4');
 INSERT INTO project(proj_num,proj_name,start_date,end_date,of_dpt) VALUES(04,'proj_d','2015-02-15','2015-04-01','dpt3');
 INSERT INTO project(proj_num,proj_name,start_date,end_date,of_dpt) VALUES(05,'proj_e','2015-02-25','2015-03-01','dpt4');
 INSERT INTO project(proj_num,proj_name,start_date,end_date,of_dpt) VALUES(06,'proj_f','2015-02-26','2015-03-01','dpt2');
 
 #INSERT INTO table_1 VALUES(01,11,12);
 
 INSERT INTO table_1 VALUES(02,22,89);
 INSERT INTO table_1 VALUES(03,56,33);
 INSERT INTO table_1 VALUES(04,34,37);
 INSERT INTO table_1 VALUES(05,39,32);
 INSERT INTO table_1 VALUES(06,90,33);