Detailed explanation of SET data types in MySQL

MySQLSET inData TypeDetailed explanation

existDatabase DesignIn this case, we often need to store a set of predefined values, and these values ​​may have multiple cases that apply simultaneously. At this time, MySQLSETThe data type comes in handy.

SETIs a special data type in MySQL that is used to store a collection of values, and the values ​​in this collection are predefined. oneSETFields can contain zero, one or more of these predefined values, which are separated by commas when stored.String representationof.

How to define SET types

Create aSETWhen you type a column, you need to define a set of possible values. For example:

CREATE TABLE your_table (
    your_column SET('value1', 'value2', 'value3', ...)
);

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hereyour_columnAny combination of these values ​​can be stored, including none of them.

WhenSETWhen inserting data in columns of types, you can insert any combination of values ​​defined. For example:

INSERT INTO your_table (your_column) VALUES ('value1,value2'), ('value3'), ('value1,value3');

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SET type storage and retrieval

When storing,SETTypes are actually stored as integers, with each value corresponding to a bit. This expression method makesSETTypes are very efficient, especially when performing bit operations.

SearchSETWhen data of type, it will automatically convert back to comma-separated string format for easy reading.

Advantages and limitations of SET types

• Advantages:

  • Compact storage: especially when there are multiple options, useSETTypes save space.
  • Flexibility: You can easily add or delete values.

• Limitations:

  • Limitations of predefined values:SETA type can only contain up to 64 different values.
  • Update difficulty: If you need to change the possible collection of values, you may need to modify the definition of the entire column.

Things to note

• In useSETWhen typed, make sure it does fit your data model. In some cases, using association tables may be a better choice.
• Considering possible future changes, if you expect the value set to change frequently,SETTypes may not be the best choice.

MySQLSETTypes are a powerful and flexible data type suitable for scenarios where fixed value collections are required.