正確な財務データに MySQL DECIMAL を使用する理由とその方法?

Mastering MySQL DECIMAL for Precise Data Management

When dealing with financial data or any application where numerical precision is crucial, MySQL's DECIMAL data type comes into play. Unlike DOUBLE columns, which are floating-point and prone to approximations, DECIMAL provides exact representations with greater accuracy.

Creating a DECIMAL Column with a Specific Range

As you require values to range from 00.0001 to 99.9999, the following SQL statement will create a DECIMAL column that meets this criterion:

CREATE TABLE your_table(
    your_column DECIMAL(6,4) NOT NULL
);

Understanding DECIMAL Syntax

The DECIMAL data type follows the format DECIMAL(M, D), where M represents the maximum number of digits (precision) and D indicates the number of digits to the right of the decimal point (scale). In our example, DECIMAL(6,4) means values can range from -99.9999 to 99.9999 with a precision of 6 and a scale of 4.

Unsigned DECIMAL versus Signed DECIMAL

You can also create an UNSIGNED DECIMAL column, which only accepts positive values from 0.0000 to 99.9999. To do so, replace NOT NULL with UNSIGNED NOT NULL in the CREATE TABLE statement.

Customizing Precision and Scale

Depending on your specific requirements, you can adjust the precision and scale to match the range and accuracy you need. For instance, a column that accommodates values from -9999.99 to 9999.99 would use the DECIMAL(6,2) data type.

Additional Notes

• MySQL versions 5.0.3 and above fully support DECIMAL.
• For more in-depth information on MySQL DECIMAL, refer to the official documentation.
• Since MySQL 8.0.17, unsigned is deprecated for FLOAT, DOUBLE, and DECIMAL columns.

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