CREATE TYPE 功能描述 注意事项 语法格式 参数说明 示例 相关链接 CREATE TYPE 功能描述 在当前数据库中定义一种新的数据类型。定义数据类型的用户将成为该数据类型的拥有者。类型只适用于行存表 有五种形式的CREATE TYPE，分别为：复合类型、基本类型、shell类型、枚举类型和集合类型。 复合类型 复合类...

Type restrictions Restrictions from instance variables self restriction Classes as restrictions Type restrictions in splats Free variables Splat type restrictions Type res...

Type inference With type restrictions Without type restrictions 1. Assigning a literal value 2. Assigning the result of invoking the class method new 3. Assigning a variable th...

Type reflection Type reflection Crystal provides basic methods to do type reflection, casting and introspection.

Type restrictions Restrictions from instance variables self restriction Classes as restrictions Type restrictions in splats Free variables Type restrictions Type restrictio...

JSON 类型 JSON 类型 JSON 类型可以存储 JSON 这种半结构化的数据，相比于直接将 JSON 存储为字符串，它的好处在于： 使用 Binary 格式进行序列化，对 JSON 的内部字段的查询、解析加快； 多了 JSON 合法性验证的步骤，只有合法的 JSON 文档才可以放入这个字段中； JSON 字段本身上，并不能创建索引。相反...

Type Casting Introduction Problem Type Casting in UIKit Human Class Human Subclass Type Casting Upcasting Upcasting Example in Swift Struct Downcasting Force Downcasting I...

object type object type TypeScript did not have a type that represents the non-primitive type, i.e. any thing that is not number string boolean symbol null undefined . Ent...

DROP TYPE Synopsis Syntax Diagram Grammar Semantics Examples See also DROP TYPE Synopsis The DROP TYPE statement removes an existing user-defined data type. Syntax...

CREATE TYPE Synopsis Syntax create_composite_type create_enum_type create_range_type create_base_type create_shell_type composite_type_elem range_type_option base_type_opti...