SQL FLOAT4

What is SQL FLOAT4?

FLOAT4 is a 32-bit single-precision floating-point data type used to store approximate numeric values.

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Compatible dialects for SQL FLOAT4: PostgreSQL: Yes (native alias for REAL) MySQL: Use FLOAT or FLOAT(24) instead SQL Server: REAL is equivalent SQLite: Uses dynamic typing; FLOAT affinity maps to REAL Oracle: BINARY_FLOAT is similar but not identical

SQL FLOAT4 Full Explanation

FLOAT4 (sometimes written as FLOAT(24) or REAL) stores approximate numeric values using the IEEE-754 single-precision (4-byte) format. It offers roughly 6-7 decimal digits of precision, a value range of about 1E-37 to 1E+37, and can represent special values such as NaN and Infinity in PostgreSQL. Because it is an approximate type, arithmetic is fast but subject to rounding error, so it is unsuitable for exact financial calculations. In PostgreSQL, FLOAT4 is merely an alias for REAL; it cannot accept an explicit precision argument. Casting to and from other numeric types is allowed, and division by zero returns Infinity or raises an error depending on the dialect’s settings. Always remember that equality comparisons on FLOAT4 can yield unexpected results due to binary rounding.

SQL FLOAT4 Syntax

column_name FLOAT4
-- or
CAST(expression AS FLOAT4)

SQL FLOAT4 Parameters

Example Queries Using SQL FLOAT4

-- 1. Creating a table with FLOAT4
CREATE TABLE sensor_readings (
    id SERIAL PRIMARY KEY,
    temperature FLOAT4,
    humidity FLOAT4
);

-- 2. Inserting values
INSERT INTO sensor_readings (temperature, humidity)
VALUES (23.456, 0.458);

-- 3. Casting
SELECT CAST(42 AS FLOAT4) AS single_precision_value;

-- 4. Arithmetic
SELECT AVG(temperature) AS avg_temp
FROM sensor_readings;

Expected Output Using SQL FLOAT4

Table is created with temperature and humidity stored as 4-byte floats.
Row is inserted; values are rounded to FLOAT4 precision.
Returns 42.0 as a single-precision float.
AVG returns a FLOAT4 result representing the mean temperature.

Use Cases with SQL FLOAT4

Store scientific sensor data where minor rounding is acceptable
Speed up large analytic workloads that do not require double precision
Reduce disk or memory footprint compared to FLOAT8 or NUMERIC

Common Mistakes with SQL FLOAT4

Expecting exact decimal representation or perfect equality comparisons
Assuming FLOAT4 supports arbitrary precision like NUMERIC
Forgetting that FLOAT4 silently rounds values beyond ~7 significant digits
Mixing FLOAT4 with NUMERIC in arithmetic without explicit casting, leading to implicit upcasting or precision loss

First Introduced In

PostgreSQL 6.5

Frequently Asked Questions

What precision does FLOAT4 offer?

It supports roughly 6-7 decimal digits because it relies on IEEE-754 single-precision storage.

Is FLOAT4 identical to REAL in PostgreSQL?

Yes. FLOAT4 is an alias for REAL, so they behave the same in every context.

Can I define FLOAT4 with a custom precision, like FLOAT4(10)?

No. PostgreSQL does not accept a precision argument for FLOAT4. Specify NUMERIC or FLOAT(p) if you need explicit precision.

Why do equality checks on FLOAT4 sometimes fail?

Binary rounding can cause two values that look equal in decimal form to differ slightly in binary, making direct equality comparisons unreliable.