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<