Gorm Struct 和 MySQL 的类型映射对照表

以下是 Gorm Struct 和 MySQL 的类型映射对照表：

Gorm Struct 类型	MySQL 数据库类型
string	varchar
bool	boolean
int, int8, int16, int32	int, tinyint, smallint, mediumint, int
uint, uint8, uint16, uint32	int unsigned, tinyint unsigned, smallint unsigned, mediumint unsigned, int unsigned
float32, float64	float, double, decimal
time.Time	datetime, date, timestamp
[]byte	blob, binary
[]string	varchar

如果需要自定义类型映射，可以使用 .SetVarColunm() 和 .SetTypeMap() 方法。例如：

// 设置某个字段类型为 JSON
model := DB.Model(&Product{})
model.SetVarColunm("detail", "json")
model.AutoMigrate(&Product{})

// 自定义类型映射
gorm.DefaultForeignKeyUpdateMethod = "CASCADE"
db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{
  NamingStrategy: schema.NamingStrategy{
    TablePrefix:   "tb_",
    SingularTable: true,
  },
  CreateBatchSize:          10,
  DisableForeignKeyConstraintWhenMigrating: true,
  ForeignKeyConstraintWhenMigrating:         true,
  PrepareStmt:              true,
  FullSaveAssociations:     true,
  Logger:                   logger.Default.LogMode(logger.Info),
  SkipDefaultTransaction:   false,
  QueryFields:              true,
  AllowGlobalUpdate:        false,
  DisableNestedTransaction: true,
  DisableAutomaticPing:     false,
  // 定义类型映射
  TypeMap: map[string]string {
      "bool":   "tinyint",
      "string": "varchar(255)",
  },
})