@Column(columnDefinition)的使用
columnDefinition属性的使用:
@Table(name = "CUSTOMERS") @Entity public class Customer { @Column(name = "ID") @GeneratedValue(strategy = GenerationType.AUTO) @Id private Integer id; @Column(name = "Name") private String name; @Column(name = "Email",columnDefinition="varchar(128) not null") private String email; @Column(name = "Age") private int age; ...... }
数据库DDL:
CREATE TABLE `customers` ( `ID` int(11) NOT NULL AUTO_INCREMENT, `Age` int(11) DEFAULT NULL, `Email` varchar(128) NOT NULL, `Name` varchar(255) DEFAULT NULL, PRIMARY KEY (`ID`) ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
columnDefinition可以指定创建表时一些SQL语句,比如这里可以一次性指定,varchar长度128,且不能为空
当然,相同的结果可以通过nullable和length属性结合实现
@Table(name = "CUSTOMERS") @Entity public class Customer { @Column(name = "ID") @GeneratedValue(strategy = GenerationType.AUTO) @Id private Integer id; @Column(name = "Name") private String name; @Column(name = "Email", nullable = true, length = 128) private String email; @Column(name = "Age") private int age; ...... }
数据库DDL:
CREATE TABLE `customers` ( `ID` int(11) NOT NULL AUTO_INCREMENT, `Age` int(11) DEFAULT NULL, `Email` varchar(128) DEFAULT NULL, `Name` varchar(255) DEFAULT NULL, PRIMARY KEY (`ID`) ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
columnDefinition属性的特殊使用:
编程语言中字符串一般都用String表示,但是数据库中varcahr数值类型有长度限制,一旦需要大文本,则需要text数值类型
但是String类型默认映射的数值类型是varchar,columnDefinition可以进行额外指定
@Table(name = "CUSTOMERS") @Entity public class Customer { @Column(name = "ID") @GeneratedValue(strategy = GenerationType.AUTO) @Id private Integer id; @Column(name = "Name") private String name; @Column(name = "Email", nullable = true, length = 128) private String email; @Column(name = "Age") private int age; @Column(name = "Remark",columnDefinition="text") private String remark; ...... }
数据库DDL:
CREATE TABLE `customers` ( `ID` int(11) NOT NULL AUTO_INCREMENT, `Age` int(11) DEFAULT NULL, `Email` varchar(128) DEFAULT NULL, `Name` varchar(255) DEFAULT NULL, `Remark` text, PRIMARY KEY (`ID`) ) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
remark列数值类型是text,而Name和Email默认是varcahr