-- 查詢5大洲國家總數 SELECT continent,COUNT(*) FROM country GROUP BY continent;-- 演示臨時表 CREATE TEMPORARY TABLE tmp_table ( continent VARCHAR(20), COUNT INT );INSERT INTO tmp_table SELECT 'Asia' AS 'continent',COUNT(*) FROM country WHERE continent = 'Asia'; INSERT INTO tmp_table SELECT 'North America' AS 'continent',COUNT(*) FROM country WHERE continent = 'North America'; INSERT INTO tmp_table SELECT 'Europe' AS 'continent',COUNT(*) FROM country WHERE continent = 'Europe'; INSERT INTO tmp_table SELECT 'South America' AS 'continent',COUNT(*) FROM country WHERE continent = 'South America'; INSERT INTO tmp_table SELECT 'Oceania' AS 'continent',COUNT(*) FROM country WHERE continent = 'Oceania'; INSERT INTO tmp_table SELECT 'Antarctia' AS 'continent',COUNT(*) FROM country WHERE continent = 'Antarctia';-- 給學生表添加一列 密碼 ALTER TABLE student ADD PASSWORD CHAR(32) NOT NULL AFTER student_no;DROP TEMPORARY TABLE passwd_temp; CREATE TEMPORARY TABLE passwd_temp SELECT student_no s_no,MD5(student_no) pwd FROM student; SELECT * FROM passwd_temp;UPDATE student SET PASSWORD = (SELECT pwd FROM passwd_temp WHERE student_no = s_no);SELECT * FROM student;-- 作業: -- 不用臨時表 嘗試實現同樣功能

轉載于:https://www.cnblogs.com/bchen/p/7426309.html

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