The difference between varchar and char in mysql

The difference between VARCHAR and CHAR in MySQL: storage space allocation: VARCHAR is dynamically allocated, saving space; CHAR is fixedly allocated, not saving space. Padding: VARCHAR is not padded, CHAR is padded with spaces. Comparison: VARCHAR compares actual data, CHAR compares fixed length (including spaces). Index: VARCHAR indexes actual data, CHAR indexes fixed length (including spaces). Efficiency: VARCHAR insertion and update are efficient, and CHAR query is efficient. Selection principle: Storage space is important and data length varies greatly, so choose VARCHAR. Comparison sorting exact match, data length is fixed, select CHAR. Create an index,

The difference between VARCHAR and CHAR in MySQL

VARCHAR and CHAR in MySQL are both variable length string data type, but they have some key differences in how they are stored and processed.

1. Storage space

• VARCHAR: Dynamically allocate space according to the actual length of stored data, which can save storage space.
• CHAR: Always allocate a fixed length of space, regardless of the actual data length.

2. Padding

• VARCHAR: Do not fill in spaces and end with actual data.
• CHAR: Will be padded with spaces to a fixed length.

3. Comparison

• VARCHAR: Compare according to the actual data length, ignoring trailing spaces.
• CHAR: Compare according to fixed length, including trailing spaces.

4. Index

• VARCHAR index only indexes the actual data to improve query efficiency.
• CHAR indexes index the entire fixed length, even if it contains spaces.

5. Efficiency

• VARCHAR: Due to dynamic allocation of space, insert and update operations may be more efficient than CHAR.
• CHAR: Query operations may be more efficient than VARCHAR due to fixed length.

Which data type to choose?

Choose VARCHAR or CHAR depending on specific needs:

• If storage space is critical, and data length varies greatly, use VARCHAR .
• If comparison or sorting requires an exact match, and the data length is fixed, use CHAR.
• If you need to create an index, and you can sacrifice some query efficiency in exchange for smaller storage space, use VARCHAR.

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