mysql 查询首字母

SELECT LEFT(name, 1) AS first_letter FROM users;

SELECT SUBSTRING(name, 1, 1) AS first_letter FROM users;

SELECT LEFT(name, 1) AS first_letter FROM users WHERE name IS NOT NULL;

SELECT LEFT(TRIM(name), 1) AS first_letter FROM users;

-- 创建示例表
CREATE TABLE users (
    id INT PRIMARY KEY,
    name VARCHAR(255)
);

-- 插入示例数据
INSERT INTO users (id, name) VALUES (1, 'Alice');
INSERT INTO users (id, name) VALUES (2, 'Bob');
INSERT INTO users (id, name) VALUES (3, 'Charlie');
INSERT INTO users (id, name) VALUES (4, ' ');

-- 查询首字母并处理空值和非字母字符
SELECT 
    id,
    LEFT(TRIM(name), 1) AS first_letter
FROM 
    users;