Detailed explanation of the storage method of boolean values ​​(true and false) in the database

1. TINYINT

describe

In many database management systems, such as MySQL,TINYINTis used to represent a boolean value. This is becauseTINYINTThe space is small and can be easily mapped to0and1。

value

• 0representfalse
• 1representtrue

Storage size

• TINYINTTakes up 1 byte of storage space.

Example

CREATE TABLE example (
    is_active TINYINT(1) NOT NULL
);

Applicable scenarios

In MySQL,TINYINT(1)It is a standard way to represent boolean values, especially suitable for storing simple boolean states.

2. BOOLEAN or BOOL

describe

Some database systems (such as PostgreSQL and SQLite) provide native Boolean data types calledBOOLEANorBOOL. These types directly support storing boolean valuestrueandfalse, making database design more intuitive and easy to understand.

value

• truerepresenttrue
• falserepresentfalse

Storage size

• Storage implementations rely on specific database systems, but usually use smaller storage space.

Example

CREATE TABLE example (
    is_active BOOLEAN NOT NULL
);

Applicable scenarios

If you are using PostgreSQL or SQLite, use it directlyBOOLEANType is the most intuitive choice. It is both concise and semantic, making it easier to read and maintainable code.

3. BIT

describe

In some databases (such as SQL Server), you can useBITType to represent boolean values.BITThe type stores binary bits, usually0or1to represent the boolean value.

value

• 0representfalse
• 1representtrue

Storage size

• EachBITType values ​​occupy 1 bit of storage space, but in the database table, multipleBITValues ​​are usually packaged by bytes, thereby optimizing storage space.

Example

CREATE TABLE example (
    is_active BIT NOT NULL
);

Applicable scenarios

In SQL Server,BITTypes are very suitable for storing boolean values. It saves space and can perform storage and query operations efficiently.

4. CHAR or VARCHAR

describe

In some special cases, it can also be usedCHARorVARCHARType to store boolean values. Although this method is not common and is usually not recommended, it can be stored by storing strings."true"or"false"to implement boolean logic.

Storage size

• Stores the actual length of a string, usually 4 or 5 characters ("true"or"false"）。

Example

CREATE TABLE example (
    is_active CHAR(5) NOT NULL
);

Applicable scenarios

This practice is less common and is not recommended because it increases the overhead of storage space and reduces the readability of the code. This method is usually only chosen if it needs to be compatible with external systems or if it is done with some special treatment.

How to choose the right boolean storage type?

When choosing a type to store a Boolean value, we need to consider the following factors:

1. Compatibility

Ensure that the selected boolean type is compatible with the database system used. For example, it is usually used in MySQLTINYINT, and is used in PostgreSQLBOOLEAN。

2. Storage efficiency

• TINYINTandBOOLEAN(In PostgreSQL and SQLite) is usually more space-saving and is suitable for most scenarios.
• BITTypes are more efficient for SQL Server because they take up less storage space.

3. Readability and maintainability

Use native boolean types (e.g.BOOLEAN) can improve the readability and maintainability of the code, avoiding the like"true"and"false"Such string values ​​can directly reflect the Boolean meaning of the data.

4. Performance

Types with smaller storage space (such asBITandTINYINT) may have more performance advantages, especially when it is necessary to store a large number of boolean values.

Summarize

In database design, the most commonly used Boolean storage types are:

• MySQL：TINYINT(1)
• PostgreSQL and SQLite：BOOLEAN
• SQL Server：BIT

Choosing the right type requires not only compatibility and storage efficiency, but also code readability and maintenance. In general, use the database native boolean type (e.g.BOOLEAN) is usually the best choice.

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