Usage of char in mysql

The CHAR data type is used to store fixed-length characters. Its features include: allocating predefined storage space regardless of data length; filling in spaces when the actual data length is insufficient; search and comparison operations are fast, but may waste storage space; Suitable for scenarios that require fixed length data, alignment or precise length guarantee.

CHAR data type

The CHAR data type is used to store fixed-length characters. Unlike the variable-length VARCHAR type, the CHAR type is allocated a predefined amount of space, regardless of how much space is actually used by the data.

Usage

The syntax is:

<code class="sql">CHAR(length)</code>

Among them, length specifies the maximum length of the character column.

Features

• Fixed length: The allocated storage space will not change based on the actual length of the data.
• Padding spaces: If the actual data length is less than the specified length, fill it with spaces to the maximum length.
• Efficiency: Faster for lookup or comparison operations due to fixed length.
• Waste of storage space: Since the allocated storage space has nothing to do with the data length, storage space may be wasted.

Usage scenarios

CHAR type is suitable for the following scenarios:

• Storage data that requires a fixed length, such as postal code or Product Code.
• When data needs to be aligned with other fixed-length fields.
• When it is necessary to ensure the exact length of the string.

Example

<code class="sql">CREATE TABLE customers (
  name CHAR(30) NOT NULL,
  address CHAR(50) NOT NULL
);</code>

The above example creates a table named customers where name and address The columns are of type CHAR, with lengths of 30 and 50 characters respectively.

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