在Oracle中,可以使用JOIN語(yǔ)句將多個(gè)表連接起來(lái),并對(duì)結(jié)果集進(jìn)行數(shù)據(jù)統(tǒng)計(jì)
CREATE TABLE employees (
id INT PRIMARY KEY,
name VARCHAR(50),
department_id INT
);
CREATE TABLE departments (
id INT PRIMARY KEY,
name VARCHAR(50)
);
INSERT INTO employees (id, name, department_id) VALUES (1, 'Alice', 101);
INSERT INTO employees (id, name, department_id) VALUES (2, 'Bob', 102);
INSERT INTO employees (id, name, department_id) VALUES (3, 'Charlie', 101);
INSERT INTO departments (id, name) VALUES (101, 'HR');
INSERT INTO departments (id, name) VALUES (102, 'IT');
SELECT d.name AS department_name, COUNT(e.id) AS employee_count
FROM employees e
JOIN departments d ON e.department_id = d.id
GROUP BY d.name;
這個(gè)查詢將返回以下結(jié)果:
DEPARTMENT_NAME EMPLOYEE_COUNT
--------------- --------------
HR 2
IT 1
在這個(gè)示例中,我們使用了INNER JOIN將employees表和departments表連接起來(lái),然后使用GROUP BY子句按部門名稱分組,并使用COUNT函數(shù)統(tǒng)計(jì)每個(gè)部門的員工數(shù)量。你可以根據(jù)需要修改查詢以滿足你的統(tǒng)計(jì)需求。