What are the unsigned constraint keywords in mysql?

The keywords used to specify unsigned constraints in MySQL are: UNSIGNED: allows positive values ​​and zero. UNSIGNED ZEROFILL: Positive values ​​and zeros are allowed, and all values ​​are left-padded with zeros to match the column length.

Unsigned constraint keyword in MySQL

Unsigned constraint is used to limit the column to only contain non-negative values value. The keywords used to specify unsigned constraints in MySQL are:

• UNSIGNED
• UNSIGNED ZEROFILL

UNSIGNED

Meaning: Allow positive values ​​and zeros
Syntax: Column name UNSIGNED

For example: id INT UNSIGNED

UNSIGNED ZEROFILL

Meaning: Positive values ​​and zero are allowed, and All values ​​are left padded with zeros to match the column length
Syntax: Column name UNSIGNED ZEROFILL

Example: account_number BIGINT UNSIGNED ZEROFILL

Usage scenarios

Unsigned constraints are usually used to store non-negative values, such as:

• ID and counter
• Currency amount
• Natural number (greater than 0)

Advantages

• Ensure data integrity and prevent incorrect input of negative values
• Optimize storage space because unsigned integers generally occupy fewer bytes
• Improve query performance because the database can take advantage of unsigned constraints to optimize indexes

Note

• Unsigned constraints cannot be used with floating point types
• Converting existing columns to unsigned types may result in data loss, as negative values ​​will become Positive values
• Left padded with zerosUNSIGNED ZEROFILL Constraint only applies to integer types

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