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Suppose if create a database with utf8 character set and created table and inserted data. Here my doubt is if the character is 1 byte then it will occupy only 1 byte or it will occupy 3 bytes because of utf8 character set

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Depends on a character. Some need one byte, some - four. See http://www.fileformat.info/info/charset/UTF-8/list.htm . MySQL has two UFT8 character sets:

mysql> SHOW CHARACTER SET like 'UTF8%';
+---------+---------------+--------------------+--------+
| Charset | Description   | Default collation  | Maxlen |
+---------+---------------+--------------------+--------+
| utf8    | UTF-8 Unicode | utf8_general_ci    |      3 |
| utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci |      4 |
+---------+---------------+--------------------+--------+
2 rows in set (0.01 sec)

If a character is a one byte, it will use one byte in memory and on a disk. If four - then four. Plus the string will use one or two bytes to encode length of the string. Note, that utf8 character set cannot encode all UTF8 characters.

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CHAR(n) -- Depending on the vintage of your copy of MySQL and the ROW_FORMAT, CHAR may allocate a full 3 bytes per character.

VARCHAR(n) -- This will occupy one or two bytes for a length, plus only as many bytes are needed. That is each character will occupy 1, 2, or 3 bytes for the CHARACTER SET utf8 (utf8mb3).

In general, you should go for utf8mb4, with a max of 4 bytes per character.

After you have inserted some text, do

SELECT col,
       HEX(col),
       LENGTH(col),      -- number of bytes
       CHAR_LENGTH(col)  -- number of characters
    FROM ... WHERE ...;

This should let you see for yourself what is going on.

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From MySql documentation:

Requires a maximum of four bytes per multibyte character.

Or, if your database character encoding is set as utf8mb3:

Requires a maximum of three bytes per multibyte character.

So, yes, an utf8 character will occupy the same size in your database as it would have. No more, no less.

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