Internal Handling of DECIMAL(M, D) vs FLOAT and DOUBLE
MySQL stores DECIMAL values as exact numeric data using precise decimal representation, while FLOAT and DOUBLE use approximate floating-point binary formats. This results in differences in storage, precision, and accuracy.
DECIMAL uses exact decimal storage with base-10 representation.
M = total digits; D = digits after the decimal point.
Digits are packed in groups of 9, stored in 4-byte chunks for efficiency.
No binary rounding errors; values remain exact.
Ideal for financial calculations requiring accuracy.
Use IEEE 754 floating-point binary representation.
FLOAT uses 4 bytes; DOUBLE uses 8 bytes.
Values are stored in binary (base-2), not base-10.
Cannot store many decimals exactly (e.g., 0.1).
Faster but less precise due to approximation.
DECIMAL stores exact values; FLOAT/DOUBLE store approximate values.
DECIMAL storage varies with digit count; FLOAT/DOUBLE have fixed size.
FLOAT/DOUBLE offer speed and range; DECIMAL offers precision.
DECIMAL is preferred for financial data; FLOAT/DOUBLE for scientific computations.