如果特定列对同一员工不可用，则插入Mysql

-- 创建员工表
CREATE TABLE employees (
    id INT PRIMARY KEY,
    name VARCHAR(50),
    age INT,
    salary DECIMAL(10, 2),
    specific_column VARCHAR(50) -- 特定列
);

-- 插入数据
INSERT INTO employees (id, name, age, salary, specific_column)
VALUES (1, 'John Doe', 30, 5000.00, 'Specific Value');

-- 检查特定列是否可用
IF (SELECT COUNT(*) FROM employees WHERE id = 1 AND specific_column IS NULL) > 0 THEN
    -- 特定列不可用，设置默认值或NULL
    INSERT INTO employees (id, name, age, salary, specific_column)
    VALUES (2, 'Jane Smith', 25, 4000.00, NULL);
ELSE
    -- 特定列可用，直接插入数据
    INSERT INTO employees (id, name, age, salary, specific_column)
    VALUES (2, 'Jane Smith', 25, 4000.00, 'Specific Value');
END IF;