Usage of enum in mysql

The ENUM data type in MySQL is used to store a predefined collection of values, allowing only options within a specified range. ENUM can be defined explicitly (CREATE TABLE) or implicitly (INSERT). Using ENUM ensures data integrity, space savings, and ease of querying. But it has the problem of limited value set, and querying a large number of values ​​may be slow.

ENUM data type in MySQL

ENUM is a MySQL data type used to store a collection of predefined values. It is used to represent a limited and non-repeating set of options, similar to enumeration types in other programming languages.

Features

• Only allows storage of predefined values
• Use commas to separate values ​​
• If the inserted value is not in the predefined set , an error occurs
• Can be defined explicitly or implicitly

Define ENUM

The ENUM data type can be defined in two ways:

Explicit definition:

<code class="sql">CREATE TABLE table_name (
  column_name ENUM('value1', 'value2', 'value3')
);</code>

Implicit definition:

<code class="sql">INSERT INTO table_name (column_name) VALUES ('value1');</code>

In this case, MySQL will automatically create ENUM data type and use the inserted value as a predefined set of values.

Using ENUM

After the ENUM data type is defined, you can use it to store any value that conforms to the predefined values. For example:

<code class="sql">INSERT INTO table_name (column_name) VALUES ('value2');</code>

Advantages

• Data integrity: Ensures that data is only stored in predefined collections, preventing value inconsistencies.
• Space efficiency: Since an index is stored instead of a string, space can be saved compared to using the VARCHAR type to store the same information.
• Easy to query: Specific values ​​can be easily queried using the IN and NOT IN operators.

Disadvantages

• Limited value collection: The value collection of ENUM is predefined. If you need to add new values, you need to modify the data type definition. and existing data.
• Query speed: For ENUMs containing a large number of values, querying using the IN and NOT IN operators may slow down.

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