What Does Enum Mean in Mysql?

What does ENUM mean in MySQL?

The ENUM data type in MySQL is a string object. It allows us to limit the value chosen from a list of permitted values in the column specification at the time of table creation. It is short for enumeration, which means that each column may have one of the specified possible values.

Why is ENUM bad MySQL?

The practical drawback is extendability. You can’t add a value to the list without updating the entire table. You can’t mark values to be historic. The list of values is limited.

What is the difference between ENUM and set in MySQL?

Difference between SET and ENUM. The difference between SET and ENUM is that SET column can contain multiple values and whereas an ENUM can hold only one of the possible values. The SET type is similar to ENUM whereas the SET type is stored as a full value rather than an index of a value as with ENUM.

Why is ENUM not good?

Why/When you should NOT use the ENUM type 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. Portability is a concern.

What does enum mean in SQL?

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.

What is an enum value?

An enum type is a special data type that enables for a variable to be a set of predefined constants. The variable must be equal to one of the values that have been predefined for it. Common examples include compass directions (values of NORTH, SOUTH, EAST, and WEST) and the days of the week.

Should I store enum in database?

By keeping the enum in your database, and adding a foreign key on the table that contains an enum value you ensure that no code ever enters incorrect values for that column. This helps your data integrity and is the most obvious reason IMO you should have tables for enums.

Are enums bad practice?

It provides strong type safety. They have some disadvantages at times, but this is really typically related to situations where every possible option is not known in advance. If you have a fixed set of options, such as your example, then strong typed enums are a good thing, and should not be avoided.

Is index a constraint in SQL?

Is an index a constraint? Not really, but a unique index has the same effect as a unique constraint on the same columns. So, you can think of a unique index as implementing a unique constraint.

How do you represent an ENUM and set internally in MySQL?

MySQL stores ENUM string values internally as decimal integers of values 1 through n for a column with n members in the enumeration. MySQL represents SET string values as a bitmap using one bit per value, thus the values are stored internally as 1, 2, 4, 8… up to 65,535 for a maximum of 64 members.

Should I use enums?

Enums are lists of constants. When you need a predefined list of values which do represent some kind of numeric or textual data, you should use an enum. You should always use enums when a variable (especially a method parameter) can only take one out of a small set of possible values.

Are enums good practice?

Best Practice #1: Use enums to eliminate “magic numbers” from your code. Make your code explicit and easy to read. Pitfall #1: Using “magic numbers” leads to hard-to-understand code and business logic errors. Enums will eliminate these issues.