What is an ENUM MySQL?

An ENUM is a string object with a value chosen from a list of permitted values that are enumerated explicitly in the column specification at table creation time.

Is MySQL ENUM bad?

ENUM is great for data that you know will fall within a static set. If you are using Mysql 5+, storage is almost always better with an ENUM type for data in a static set, as the official MySQL reference shows. Not to mention that the data is readable, and you have an extra layer of validation.

How are enums stored in MySQL?

The ENUM data type is stored in two locations: the set of values is stored in the table metadata; in each row, only the set index is stored, as integer, which requires one byte for enums up to 255 entries large, then two for up to 65535 entries (see MySQL reference)

What is an ENUM and set data type in MySQL?

ENUM and SET types are the special string types in which values are chosen from the fixed list of values set in the database table. MySQL provides two data types ENUM and SET types. Both ENUM and SET types allow us to specify a list of possible values for a column with a default value.

How do you declare an enum in SQL?

USE WorldofWarcraft; CREATE TABLE [users] ( ID INT NOT NULL IDENTITY(1,1) PRIMARY KEY, username varchar(255), password varchar(255), mail varchar (255), rank ENUM (‘Fresh meat’, ‘Intern’,’Janitor’,’Lieutenant’,’Supreme being’)DEFAULT ‘Fresh meat’, );

Can we use VARCHAR2 in MySQL?

MySQL supports the CHAR and VARCHAR type for character type with a length that is less than 65,535 bytes. From MySQL 5.0. 3 on, the maximum length for the VARCHAR type is 65,535 bytes. Oracle supports four character types: CHAR, NCHAR, NVARCHAR2 and VARCHAR2.

Why is ENUM bad?

The problem with enums is described in Fowler’s Refactoring, where it is considered a code smell. It has nothing to do with type safety, but rather that it forces you to sprinkle switch statements all over your code, thus violating the DRY Principle.

Why is ENUM not good?

Why/When you should NOT use the ENUM type When ENUM type is not fixed. When ENUM type has a long list of values. When your application does not know the list of ENUM values. ENUM type is not reusable.

Why do we create enum in Java?

Enums are used when we know all possible values at compile time, such as choices on a menu, rounding modes, command line flags, etc. It is not necessary that the set of constants in an enum type stay fixed for all time. In Java (from 1.5), enums are represented using enum data type.

How are enums stored in database?

First of all, in order to save enum values in a relational database using JPA, you don’t have to do anything. By default, when an enum is a part of an entity, JPA maps its values into numbers using the ordinal() method. What it means is that without customizations JPA stores enum value as numbers.

Is enum a collection?

An EnumSet is a specialized Set collection to work with enum classes. It implements the Set interface and extends from AbstractSet: Even though AbstractSet and AbstractCollection provide implementations for almost all the methods of the Set and Collection interfaces, EnumSet overrides most of them.

Does SQL support enums?

In sql server there is no datatype like mySQL enum. However you can achieve the same using CHECK constraint.