如何利用MySQL设计规约提高技术同学的数据库性能？

-- 在user表的username字段上建立索引
ALTER TABLE user ADD INDEX idx_username (username);

-- 创建范围分区表
CREATE TABLE sales (
    id INT PRIMARY KEY,
    amount DECIMAL(10,2)
) PARTITION BY RANGE (id) (
    PARTITION p0 VALUES LESS THAN (1000),
    PARTITION p1 VALUES LESS THAN (2000),
    PARTITION p2 VALUES LESS THAN (MAXVALUE)
);

-- 查询user表中的id和username字段
SELECT id, username FROM user;

-- 查询user表和order表中的关联数据
SELECT u.username, o.order_no
FROM user u
JOIN order o ON u.id = o.user_id;

// Java代码示例
Connection conn = DriverManager.getConnection(url, username, password);
conn.setAutoCommit(false);

try {
    // 执行一系列SQL操作
    // ...
    
    conn.commit();
} catch (SQLException e) {
    conn.rollback();
} finally {
    conn.setAutoCommit(true);
    conn.close();
}

-- 设置事务隔离级别为READ COMMITTED
SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;

// Java代码示例
String sql = "SELECT * FROM user WHERE id = ?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, 1);
ResultSet rs = pstmt.executeQuery();

// Java代码示例
String sql = "INSERT INTO user (username, password) VALUES (?, ?)";
PreparedStatement pstmt = conn.prepareStatement(sql);

for (User user : userList) {
    pstmt.setString(1, user.getUsername());
    pstmt.setString(2, user.getPassword());
    pstmt.addBatch();
}

pstmt.executeBatch();