MySQL の CHARACTER_LENGTH() 関数の使用法の詳細な説明

CHARACTER_LENGTH(str)

SELECT CHARACTER_LENGTH('Cat');

+-------------------------+
| CHARACTER_LENGTH('Cat') |
+-------------------------+
|                       3 |
+-------------------------+

SELECT CHARACTER_LENGTH('Cat ');

+--------------------------+
| CHARACTER_LENGTH('Cat ') |
+--------------------------+
|                        4 |
+--------------------------+

SELECT 
  CHARACTER_LENGTH(TRIM('Cat ')) AS 'TRIM',
  CHARACTER_LENGTH(RTRIM('Cat ')) AS 'RTRIM';

+------+-------+
| TRIM | RTRIM |
+------+-------+
|    3 |     3 |
+------+-------+

SELECT 
  CHARACTER_LENGTH(TRIM(' Cat')) AS 'TRIM',
  CHARACTER_LENGTH(LTRIM(' Cat')) AS 'LTRIM';

+------+-------+
| TRIM | LTRIM |
+------+-------+
|    3 |     3 |
+------+-------+

SELECT CHARACTER_LENGTH(ArtistName) Result
FROM Artists
WHERE ArtistName = 'Lit';

ALTER TABLE Artists 
MODIFY COLUMN ArtistName VARCHAR(255) unicode;

SELECT CHARACTER_LENGTH(ArtistName) 
FROM Artists
WHERE ArtistName = 'Lit';