Signed vs Unsigned
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Overview
Our number system ranges from minus infinity to plus infinity, with zero in the middle. However, programming has two types of numbers: signed and unsigned. The potential to employ negative numbers is the primary difference between a signed and an unsigned number. Unsigned numbers can only have values that are equal to or greater than zero. On the other hand, signed numbers have a more natural range that covers negative and positive numbers.
Introduction
The requirement to express numeric values with limited resources drove the creation of signed vs. unsigned numbers. When utilizing 8 bits, there are only 256 possible combinations. Any value between 0 and 255 is considered an unsigned number. On the other hand, having a signed number means you've already lost a bit for representing the sign. With 7 bits, you can only have 128 permutations. Hence an 8-bit signed number's range is -128 to 127. Using unsigned numbers was the way to go if you had limited resources, which was the case in the early days of computers.
Unsigned integers range from 0 to 4,294,967,295 or around 4 billion in 32-bit integers. The signed version ranges from –2,147,483,648 to 2,147,483,647, or around -2 billion to +2 billion. The range is the same, but the values are shifted on the number line.
Difference between Signed and Unsigned in MySQL
Signed value - Variables with signed numerals can store 0, positive, and negative numbers.
Unsigned value - Variables with unsigned numerals can store only 0 and positive numbers.
Table of the Range of Values Each Integer Type Can Store Refer
| Type | Storage (Bytes) | Min signed value | Max signed value | Min unsigned value | Max unsigned value |
|---|---|---|---|---|---|
| TINYINT | 1 | -128 | 127 | 0 | 255 |
| SMALLINT | 2 | -32768 | 32767 | 0 | 65535 |
| MEDIUMINT | 3 | -8388608 | 8388607 | 0 | 16777215 |
| INT | 4 | -2147483648 | 2147483647 | 0 | 4924967295 |
| BIGINT | 8 | -9,223,372,036,854,775,808 | 9,223,372,036,854,775,807 | 0 | 18,446,744,073,709,551,615 |
Example
- To specify unsigned id-column
Here, the variable roll_no is of unsigned numeric type. Only 0 and other positive numbers are allowed. It is not capable of storing negative values.
- To specify signed column representing temperature column
Here, the temperature variable is of a signed numeric type. All negative and positive integers and zero can be stored in the temperature variable.
Conclusion
- An unsigned number contains just zero or positive values, whereas a signed number has both positive and negative numbers along with the value zero.
- The maximum value of signed numbers is half that of unsigned numbers.
- Combining signed and unsigned numbers might cause complications.
- Whether a number is signed or unsigned has no bearing on modern applications.