What Is Double Data Type in PostgreSQL?


Angela Bailey

The double data type in PostgreSQL is used to store numeric values with decimal points. It allows for the storage of both positive and negative numbers, as well as zero.

Double precision is the default double data type in PostgreSQL.

Understanding the Double Data Type

The double data type is a floating-point number that can represent a wide range of values. It is commonly used when more precision is required compared to the integer data type.

The double data type in PostgreSQL conforms to the IEEE 754 standard for floating-point arithmetic.

Declaring and Using Double Data Type

To declare a column with the double data type in PostgreSQL, you can use the DOUBLE PRECISION keyword. For example:

CREATE TABLE my_table (
    my_column DOUBLE PRECISION

You can also specify the precision and scale for more control over the range and decimal places of your double values. For example:

CREATE TABLE my_table (
    my_column DOUBLE PRECISION(10, 2)

This creates a column named my_column with a maximum of 10 digits, including 2 decimal places.

Performing Mathematical Operations on Double Values

The double data type allows you to perform various mathematical operations, such as addition, subtraction, multiplication, and division. These operations are similar to those performed on other numeric data types in PostgreSQL.

SELECT 5.6 + 2.3; -- Output: 7.9
SELECT 10.0 - 4.5; -- Output: 5.5
SELECT 3.14 * 2; -- Output: 6.28
SELECT 8.5 / 2; -- Output: 4.25

Advantages of Using Double Precision

There are several advantages to using the double data type in PostgreSQL:

  • Precision: Double precision allows for greater precision compared to the integer data type, making it suitable for scientific calculations and financial applications.
  • Range: The double data type can represent a wide range of values, including very large and very small numbers.
  • Floating-point arithmetic: The double data type follows the IEEE 754 standard, ensuring consistent results across different platforms and programming languages that support this standard.

Considerations when Using Double Data Type

While the double data type has its advantages, there are a few considerations to keep in mind:

  • Precision limitations: Although double precision provides high precision, it is still subject to limitations due to the finite number of bits used for storage. This can lead to rounding errors or loss of precision in certain calculations.
  • Comparison accuracy: When comparing double values for equality, it’s important to consider rounding errors.

    Instead of checking for exact equality, it’s often recommended to use a tolerance or range-based comparison.

  • Storage requirements: Double precision requires more storage space compared to integer data types. If storage efficiency is a concern, consider using other numeric types that better fit your requirements.

In Conclusion

The double data type in PostgreSQL is a versatile choice when precise decimal calculations are needed. It offers a wide range of values and follows the IEEE 754 standard for consistent floating-point arithmetic.

However, it’s important to be aware of its precision limitations and consider alternative data types when necessary.

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