SQL 一个查询中的多个 select count 语句

使用 SQL 中的多个 SELECT COUNT 语句进行数据统计

sql
SELECT COUNT(*) AS total_employees
FROM employees;

sql
SELECT department, COUNT(*) AS department_employees
FROM employees
GROUP BY department;

sql
SELECT COUNT(*) AS new_employees
FROM employees
WHERE hire_date >= CURDATE() - INTERVAL 1 YEAR;

sql
SELECT
  (SELECT COUNT(*) FROM employees) AS total_employees,
  (SELECT COUNT(*) FROM employees WHERE department = 'IT') AS it_department_employees,
  (SELECT COUNT(*) FROM employees WHERE hire_date >= CURDATE() - INTERVAL 1 YEAR) AS new_employees;