mysql 常用查询命令

SELECT column1, column2, ...
FROM table_name;

SELECT * FROM employees; --检索employees表中的所有记录
SELECT first_name, last_name FROM employees; --检索特定列

SELECT column1, column2, ...
FROM table_name
WHERE condition;

SELECT * FROM employees WHERE salary > 5000; --检索薪水大于5000的员工

SELECT table1.column1, table2.column2, ...
FROM table1
JOIN table2 ON table1.common_column = table2.common_column;

SELECT employees.first_name, departments.department_name
FROM employees
JOIN departments ON employees.department_id = departments.department_id;

SELECT column1, aggregate_function(column2)
FROM table_name
GROUP BY column1;

SELECT department_id, COUNT(*) as employee_count
FROM employees
GROUP BY department_id;

SELECT column1, column2, ...
FROM table_name
ORDER BY column1 ASC|DESC;

SELECT * FROM employees ORDER BY last_name ASC; --按姓氏升序排列

INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);

INSERT INTO employees (first_name, last_name, email)
VALUES ('John', 'Doe', 'john.doe@example.com');

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

UPDATE employees
SET salary = salary * 1.05
WHERE department_id = 1;

DELETE FROM table_name
WHERE condition;

DELETE FROM employees WHERE employee_id = 100;