| 用途 | 文本处理 |
|---|---|
| 常用 | CONCAT() SUBSTRING() REPLACE() TRIM() UPPER() LENGTH() CHAR_LENGTH() |
| 编码 | LENGTH 按字节，CHAR_LENGTH 按字符 |
常用示例
常用示例
SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM users;
SELECT SUBSTRING(sku, 1, 6) AS prefix FROM orders LIMIT 3;
SELECT REPLACE(phone, '-', '') AS phone_raw FROM users;
SELECT CHAR_LENGTH('中文abc') AS chars, LENGTH('中文abc') AS bytes;utf8mb4 下一个汉字 3 字节：LENGTH()=9、CHAR_LENGTH()=3，判断长度要用 CHAR_LENGTH。