一、SQL基础知识点补充

SQL DML 和 DDL

可以把 SQL 分为两个部分：数据操作语言 (DML) 和 数据定义语言 (DDL)。

SQL (结构化查询语言)是用于执行查询的语法。但是 SQL 语言也包含用于更新、插入和删除记录的语法。

查询和更新指令构成了 SQL 的 DML 部分：

• SELECT - 从数据库表中获取数据
• UPDATE - 更新数据库表中的数据
• DELETE - 从数据库表中删除数据
• INSERT INTO - 向数据库表中插入数据

SQL 的数据定义语言 (DDL) 部分使我们有能力创建或删除表格。我们也可以定义索引（键），规定表之间的链接，以及施加表间的约束。

SQL 中最重要的 DDL 语句:

• CREATE DATABASE - 创建新数据库
• ALTER DATABASE - 修改数据库
• CREATE TABLE - 创建新表
• ALTER TABLE - 变更（改变）数据库表
• DROP TABLE - 删除表
• CREATE INDEX - 创建索引（搜索键）
• DROP INDEX - 删除索引

--20180110简单SQL脚本学习--
 
相关关键字： CREATE（创建） COMMENT ON（添加注释） COLUMN（列） FLASHBACK（回退） GROUP  BY（分组） ORDER BY（排序） MODIFY（修改）
--一、表的相关操作脚本
--1.创建数据表
        --1.1常规创建表格
        CREATE TABLE STU_INFO(
        STU_ID VARCHAR(15) NOT NULL,
        STU_NAME VARCHAR(120),
        STU_CLASS VARCHAR(120),
        STU_SEX VARCHAR(10)
        );
         --1.2通过复制的方式创建表
         CREATE TABLE STU_INFO_TEMP AS SELECT * FROM STU_INFO;
         --1.3通过复制的方式但只是复制表结构不复制表的数据
          CREATE TABLE STU_INFO_TEMP AS SELECT * FROM STU_INFO WHERE 1=2;
--2.给表和字段添加注释
        COMMENT ON TABLE STU_INFO IS '2018年1月10号SOULSJIE学习SQL脚本创建的数据表 ';
        COMMENT ON COLUMN STU_INFO.STU_ID IS '学生学号';
        COMMENT ON COLUMN STU_INFO.STU_NAME IS '学生的姓名';
        COMMENT ON COLUMN STU_INFO.STU_CLASS IS '学生所属班级';
        COMMENT ON COLUMN STU_INFO.STU_SEX IS '学生的性别';
--3.修改表结构
        --2.1添加表字段
        ALTER TABLE STU_INFO ADD STU_ADD VARCHAR(120);
        --2.2修改表字段
        ALTER TABLE STU_INFO MODIFY (STU_SEX VARCHAR(6));
        --2.3删除表字段
        ALTER TABLE STU_INFO DROP (STU_ADD);
        --2.4修改表名
 
        ALTER TABLE TESTS RENAME TO STU_INFO;
        --2.5修改列名
        ALTER TABLE STU_INFO RENAME COLUMN STU_CLASS TO STU_BANJI;
--4.删除数据表
        DROP TABLE STU_INFO_TEMP;
--5.恢复被DROP的数据表
        FLASHBACK TABLE STU_INFO TO BEFORE DROP;
--6.表的截断 关键字 truncate 清空表中的数据，并且还原数据占用的内存空间
         TRUNCATE TABLE STU_INFO;
--7.表的清空  关键字 delete 清空表中的数据，但是不还原数据占用的内存空间
          DELETE FROM STU_INFO;
 
--二.数据操作脚本
        --1.1插入单条数据
        --MySQL的写法和Oracle写法一样
        INSERT INTO STU_INFO
          (STU_ID, STU_NAME, STU_CLASS, STU_SEX)
        VALUES
          ('Q', 'Q', 'Q', 'Q');
        --1.2插入多条记录数据
        --MySQL的写法INSERT INTO TABLE_NAME (COLUMN_1，COLUMN_2...,COLUMN_N) VALUES(VALUE_1，VALUES_2,...,VALUES_N),(VALUES2_1，VALUES2_2...,VALUES2_N);
        --例子：在mysql中插入多条数据INSERT INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS) VALUES ('TE','TE','15'),('TT','TT','16');
        --但是在Oracle中插入多条数据写法有不同如下：
        INSERT ALL INTO STU_INFO
        (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180301','张三','3','男')
        INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180302','李四','3','女')
        INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180303','张嘉佳','3','男')
        INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180304','李丽丽','3','女')
        INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180305','汪汪汪','3','男')
        INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180306','呵呵哈','3','女')
        SELECT 1 FROM DUAL;
        --2.删除数据
        DELETE FROM STU_INFO WHERE STU_ID='02';
        DELETE FROM STU_INFO WHERE 1=1;
        --3.修改数据
        UPDATE STU_INFO SET STU_NAME='JIE',STU_SEX='女' WHERE STU_ID='03';
        --4.简单查询数据
               --4.1查询所有数据
               SELECT * FROM STU_INFO;
               --4.2多条件查询 and关键字 逻辑与的关系
               SELECT * FROM STU_INFO WHERE STU_CLASS='3' AND STU_SEX='男';
               --4.3 or关键字 逻辑或的关系
               SELECT * FROM STU_INFO WHERE STU_CLASS='1' OR STU_CLASS='2';
               --4.4 group by 分组 注意：在同时使用order by和group by时order by应该放在末尾
               SELECT STU_ID FROM STU_INFO GROUP BY STU_ID ORDER BY STU_ID ASC;
               --4.5 order by 排序 不写降序（desc）和升序(asc)时默认为升序
               SELECT * FROM STU_INFO ORDER BY STU_CLASS DESC
               --4.6 distinct 去重复
               SELECT DISTINCT STU_ID FROM STU_SCORE;
        --5.复杂数据查询 利用group by 进行统计查询
               --5.1 AVG 求各个课程的平均值
               SELECT S.KECHENG_BIANHAO 课程编号,
                      AVG(S.KECHENG_CHENGJI) 平均分
                 FROM STU_SCORE S
                GROUP BY S.KECHENG_BIANHAO;
               --5.2 min 求各个课程的最小值
               SELECT S.KECHENG_BIANHAO 课程编号,
                      MIN(S.KECHENG_CHENGJI) 最小值
                 FROM STU_SCORE S
                GROUP BY S.KECHENG_BIANHAO;
               --5.3 max 求各个课程的最大值
               SELECT S.KECHENG_BIANHAO 课程编号,
                      SUM(S.KECHENG_CHENGJI) 最小值
                 FROM STU_SCORE S
                GROUP BY S.KECHENG_BIANHAO;
               --5.4 sum 求各科课程的总分
               SELECT S.KECHENG_BIANHAO 课程编号,
                      SUM(S.KECHENG_CHENGJI) 最小值
                 FROM STU_SCORE S
                GROUP BY S.KECHENG_BIANHAO;
               --5.5 count 总计数目
               SELECT S.KECHENG_BIANHAO 课程编号, COUNT(*) 记录条数
                 FROM STU_SCORE S
                GROUP BY S.KECHENG_BIANHAO;
               --5.6 连接查询 查询每个学生的总分
               SELECT I.STU_NAME 姓名, SUM(S.KECHENG_CHENGJI) 总分
                 FROM STU_SCORE S
                 JOIN KECHENG_INFO K
                   ON S.KECHENG_BIANHAO = K.KECHENG_BIANHAO
                 JOIN STU_INFO I
                   ON S.STU_ID = I.STU_ID
                GROUP BY I.STU_NAME;
                --5.7求C语言课程的最低分
                SELECT MIN(S.KECHENG_CHENGJI) 最低分
                  FROM KECHENG_INFO K
                  JOIN STU_SCORE S
                    ON K.KECHENG_BIANHAO = S.KECHENG_BIANHAO
                 WHERE K.KECHENG_NAME = 'C语言';
                SELECT * FROM STU_SCORE;
                SELECT * FROM KECHENG_INFO;
                --5.8左连接  LEFT JOIN 满足on之后的条件的数据才会出现在结果集中
                SELECT *
                  FROM STU_SCORE S
                  LEFT JOIN KECHENG_INFO K
                    ON S.KECHENG_BIANHAO = K.KECHENG_BIANHAO;
                --5.9右连接  RIGHT JOIN 不满足on之后的条件的数据也会出现在结果集中
                SELECT *
                  FROM STU_SCORE S
                 RIGHT JOIN KECHENG_INFO K
                    ON S.KECHENG_BIANHAO = K.KECHENG_BIANHAO;
                --5.10 全连接 FULL JOIN 是左连接和右链接两个结果的并集
                SELECT *
                  FROM STU_SCORE S
                  FULL JOIN KECHENG_INFO K
                    ON S.KECHENG_BIANHAO = K.KECHENG_BIANHAO;
-------------------------临时脚本-----------------------------------
 
--例子中用到表的创建、添加数据的SQL脚本 ---
-------------------------------创建学生信息表
 CREATE TABLE STU_INFO(
        STU_ID VARCHAR(15) NOT NULL,
        STU_NAME VARCHAR(120),
        STU_CLASS VARCHAR(120),
        STU_SEX VARCHAR(10)
        );
COMMENT ON TABLE STU_INFO IS '2018年1月10号SOULSJIE学习SQL脚本创建的数据表 ';
COMMENT ON COLUMN STU_INFO.STU_ID IS '学生学号';
COMMENT ON COLUMN STU_INFO.STU_NAME IS '学生的姓名';
COMMENT ON COLUMN STU_INFO.STU_CLASS IS '学生所属班级';
COMMENT ON COLUMN STU_INFO.STU_SEX IS '学生的性别';
--向学生信息表中添加数据
INSERT ALL INTO STU_INFO
        (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180301','张三','3','男')
        INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180302','李四','3','女')
        INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180303','张嘉佳','3','男')
        INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180304','李丽丽','3','女')
        INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180305','汪汪汪','3','男')
        INTO STU_INFO (STU_ID,STU_NAME,STU_CLASS,STU_SEX)
        VALUES
        ('180306','呵呵哈','3','女')
        SELECT 1 FROM DUAL;
 
-------------------------------创建辅助数据表--成绩表
CREATE TABLE STU_SCORE(
       STU_ID VARCHAR(12) NOT NULL,
       KECHENG_BIANHAO VARCHAR(50),
       KECHENG_CHENGJI VARCHAR(50)
);
COMMENT ON TABLE STU_SCORE IS 'soulsjie，学习连接查询创建的学生成绩表';
COMMENT ON COLUMN STU_SCORE.STU_ID IS'学生学号';
COMMENT ON COLUMN STU_SCORE.KECHENG_BIANHAO IS'课程编号';
COMMENT ON COLUMN STU_SCORE.KECHENG_CHENGJI IS'课程成绩';
--向成绩表中添加数据
INSERT ALL INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180301','0001','60')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180301','0002','62')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180302','0001','99')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180302','0002','99')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180303','0001','45')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180303','0002','15')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180304','0001','44')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180304','0002','55')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180305','0001','66')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180305','0002','55')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180306','0001','66')
INTO STU_SCORE (STU_ID,KECHENG_BIANHAO,KECHENG_CHENGJI)
VALUES ('180306','0002','88')
SELECT 1 FROM DUAL;
--给成绩表添加注释
COMMENT ON TABLE STU_SCORE IS 'soulsjie,学习连接查询创建的学生成绩表';
COMMENT ON COLUMN STU_SCORE.STU_ID IS '学生学号';
COMMENT ON COLUMN STU_SCORE.KECHENG_BIANHAO IS '课程的编号';
COMMENT ON COLUMN STU_SCORE.KECHENG_CHENGJI IS '课程的成绩';
 
-------------------------------创建辅助数据表--选课表
CREATE TABLE KECHENG_INFO (
KECHENG_BIANHAO VARCHAR(12) NOT NULL,
KECHENG_NAME VARCHAR(50)
);
COMMENT ON TABLE KECHENG_INFO IS 'soulsjie，学习连接查询创建的课程信息表';
COMMENT ON COLUMN KECHENG_INFO.KECHENG_BIANHAO IS '课程的编号';
COMMENT ON COLUMN KECHENG_INFO.KECHENG_NAME IS '课程名';
--添加选课表中的数据
INSERT ALL INTO KECHENG_INFO (KECHENG_BIANHAO,KECHENG_NAME)
VALUES
('0001','C语言')
INTO KECHENG_INFO (KECHENG_BIANHAO,KECHENG_NAME)
VALUES
('0002','JAVA')
SELECT 1 FROM DUAL;