学习mysql(1) mysql中表，字段，约束的简单操作

#删除表
DROP TABLE table2;
DROP TABLE table3;

#创建表
CREATE TABLE table1
(
id int NOT NULL AUTO_INCREMENT,
column1   int DEFAULT 0,
column2   varchar(20) DEFAULT NULL,
PRIMARY KEY(id)
)ENGINE= INNODB DEFAULT CHARSET=utf8;
CREATE TABLE table3
(
id int NOT NULL AUTO_INCREMENT,
column1   int DEFAULT 0,
column2   varchar(20) DEFAULT NULL,
PRIMARY KEY(id)
)ENGINE= INNODB DEFAULT CHARSET=utf8;

#表改名
ALTER TABLE table1 RENAME TO table2;
#增加列
ALTER TABLE table2 ADD COLUMN column3 varchar(10) DEFAULT 'hahha';
#删除列
ALTER TABLE table2 DROP COLUMN column3;
#列改名
ALTER TABLE table2 CHANGE column2 column4 varchar(15) DEFAULT '';
#增加外键
ALTER TABLE table2 ADD CONSTRAINT table2_talble3_fk FOREIGN KEY  (column1) REFERENCES table3(id);
#删除外键
ALTER TABLE table2 DROP FOREIGN KEY  table2_talble3_fk;

#删主键：先取消自增长，再删除主键
ALTER TABLE table2 CHANGE id id int;
ALTER TABLE table2 DROP PRIMARY KEY;

#增加主键,先加主键，再修改为自动增长
ALTER TABLE table2 ADD CONSTRAINT PRIMARY KEY (id);
ALTER TABLE table2 CHANGE id id int AUTO_INCREMENT;