第三章 查询入门

1.基本描述

    本章讲解SELECT语句的各个组成部分及它们之间是如何相互作用的。

2.基本样例

SELECT emp_id, fname, lname FROM employee 
WHERE lname = 'Bkadfl';

SELECT fname, lname FROM employee;

SELECT * FROM department;

SELECT dept_id, name FROM department;

SELECT name FROM department;

SELECT emp_id, 'ACTIVE', emp_id * 3.14159, UPPER(lname) FROM employee;

SELECT VERSION(), USER(), DATABASE();

SELECT emp_id, 'ACTIVE' status, emp_id * 3.14159 empid_x_pi, UPPER(lname) last_name_upper FROM employee;

SELECT emp_id, 'ACTIVE' AS status, emp_id * 3.14159 AS empid_x_pi, UPPER(lname) AS last_name_upper FROM employee;

SELECT cust_id FROM account;

SELECT DISTINCT cust_id FROM account;

SELECT e.emp_id, e.fname, e.lname FROM (SELECT emp_id, fname, lname, start_date, title FROM employee) e;

CREATE VIEW employee_vw AS 
SELECT emp_id, fname, lname, YEAR(start_date) start_year FROM employee;

SELECT emp_id, start_year FROM employee_vw;

SELECT employee.emp_id, employee.fname, employee.lname, department.name dept_name 
FROM employee INNER JOIN department ON employee.dept_id = department.dept_id;

SELECT emp_id, fname, lname, start_date, title FROM employee
WHERE title = 'Head Teller';

SELECT emp_id, fname, lname, start_date, title
FROM employee WHERE title = 'Head Teller' AND start_date > '2006-01-01';

SELECT emp_id, fname, lname, start_date, title FROM employee
WHERE title = 'Head Teller' OR start_date > '2006-01-01';

SELECT emp_id, fname, lname, start_date, title FROM employee
WHERE (title = 'Head Teller' AND start_date > '2006-01-01') OR (title = 'Teller' AND start_date > '2006-01-01');

SELECT d.name, count(e.emp_id) num_employees
FROM department d INNER JOIN employee e
ON d.dept_id = e.dept_id GROUP BY d.name 
HAVING count(e.emp_id) > 2;

SELECT open_emp_id, product_cd FROM account;

SELECT open_emp_id, product_cd FROM account ORDER BY open_emp_id;

SELECT open_emp_id, product_cd FROM account ORDER BY open_emp_id, product_cd;

SELECT account_id, product_cd, open_date, avail_balance FROM account ORDER BY avail_balance DESC;

SELECT cust_id, cust_type_cd, city, state, fed_id FROM customer ORDER BY RIGHT(fed_id, 3);

SELECT emp_id, title, start_date, fname, lname FROM employee ORDER BY 2, 5;