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  • 数据库Mysql的学习(四)-表的记录操作

     

    INSERT INTO bookcategory(category_id,category,parent_id) VALUES(1,'计算机',0);//指定插入的顺序
    

    INSERT INTO bookcategory VALUES(1,'计算机',0);//按照默认的插入

    INSERT INTO bookcategory(category_id,category,parent_id) VALUES(1,'计算机',0),(2,'xxx',3)(3,'xxxxx',4);//同时插入多条数据

    INSERT INTO bookcategory SELECT * FROM test WHERE id>5//将查询结果插入表中

    CREATE TABLE TEXT(
    category_id
    INT PRIMARY KEY AUTO_INCREMENT,
    parent_id
    INT NOT NULL
    )AUTO_INCREMENT
    =5; //auto_increment让这一列自动设置编号,默认初始值为,最后为设置初始值为5


    ALTER
    TABLE bookcategory MODIFY category_id INT AUTO_INCREMENT=X//为已有表添加自增列


    ALTER
    TABLE bookcategory MODIFY category_id INT;//去掉自增列

    //有外键关系的话添加自增,要先去掉外键关系。

    ALTER TABLE bookinfo DROP FOREIGN KEY fk_bcid//去掉外键

    ALTER TABLE bookinfo ADD CONSTRAINT fk_bcid FOREIGN KEY(bookcdategory_id) REFERENCES bookcategory(category_id);//添加外键

    SELECT price FROM bookinfo WHERE book_id=201501;//查询book_id为201501书的价格

    SELECT * FROM readerinfo//查看读者信息表

    SELECT xxx,xxx,xxx FROM readerinfo//查询指定列

    SELECT xxx,xxx,xxx FROM readerinfo WHERE press='机械工业'//设置外加条件的查询

    SELECT DISTINCT press FROM bookinfo;//显示不重复的查询

    SELECT * FROM readerinfo WHERE age IS NULL;//查询为空的列

    UPDATE readerinfo SET balance =balance -18.9*0.05 WHERE card_id='xxxxxxxx'//更新readerinfo这个表中的card_id为xxx的balance

    DELETE FROM readerinfo WHERE card_id='201531513133'//单表数据记录的删除,不加where则为全部删除

    TRUNCATE TABLE readerinfo;//删除原表再创建空表

    SELECT COUNT(*) FROM readerinfo WHERE sex=''//对查询结果的分组

    SELECT sex FROM readerinfo GROUP BY sex;//查询有多少种性别

    SELECT sex COUNT(*) FROM readerinfo GROUP BY sex;//统计每种性别的人数

    SELECT sex FROM readerinfo GROUP BY sex WHERE COUNT(sex)>3;//也可以加限制条件。统计每种性别的人数

    SELECT * FROM bookinfo ORDER BY price//对查询结果排序,默认为升序

    SELECT * FROM bookinfo ORDER BY price,store;//price相同的,按照库存排序

    SELECT * FROM bookinfo ORDER BY price ASC,store DESC;//asc升序,desc降序

    SELECT * FROM bookinfo LIMIT 3;//limit限制查询数量,偏移量为0开始,显示前三行

    SELECT * FROM bookinfo LIMIT 2,2;//显示第二条语句的后两个语句

    SELECT store,COUNT(*) FROM bookinfo GROUP BY store ORDER BY store DESC LIMIT 4;//统计库存个数,并降序排序,并查看前四条语句

    INSERT INTO bookcategory(category_id,category,parent_id) VALUES(1,'计算机',0);//指定插入的顺序
    INSERT INTO bookcategory VALUES(1,'计算机',0);//按照默认的插入
    INSERT INTO bookcategory(category_id,category,parent_id) VALUES(1,'计算机',0),(2,'xxx',3)(3,'xxxxx',4);//同时插入多条数据
    INSERT INTO bookcategory SELECT * FROM test WHERE id>5//将查询结果插入表中
    CREATE TABLE TEXT(
    category_id INT PRIMARY KEY AUTO_INCREMENT,
    parent_id INT NOT NULL
    )AUTO_INCREMENT=5; //auto_increment让这一列自动设置编号,默认初始值为,最后为设置初始值为5
    ALTER TABLE bookcategory MODIFY category_id INT AUTO_INCREMENT=X//为已有表添加自增列
    ALTER TABLE bookcategory MODIFY category_id INT;//去掉自增列
    //有外键关系的话添加自增,要先去掉外键关系。
    ALTER TABLE bookinfo DROP FOREIGN KEY fk_bcid//去掉外键
    ALTER TABLE bookinfo ADD CONSTRAINT fk_bcid FOREIGN KEY(bookcdategory_id) REFERENCES bookcategory(category_id);//添加外键
    SELECT price FROM bookinfo WHERE book_id=201501;//查询book_id为201501书的价格
    SELECT * FROM readerinfo//查看读者信息表
    SELECT xxx,xxx,xxx FROM readerinfo//查询指定列
    SELECT xxx,xxx,xxx FROM readerinfo WHERE press='机械工业'//设置外加条件的查询
    SELECT DISTINCT press FROM bookinfo;//显示不重复的查询
    SELECT * FROM readerinfo WHERE age IS NULL;//查询为空的列
    UPDATE readerinfo SET balance =balance -18.9*0.05 WHERE card_id='xxxxxxxx'//更新readerinfo这个表中的card_id为xxx的balance
    DELETE FROM readerinfo WHERE card_id='201531513133'//单表数据记录的删除,不加where则为全部删除
    TRUNCATE TABLE readerinfo;//删除原表再创建空表
    SELECT COUNT(*) FROM readerinfo WHERE sex='男'//对查询结果的分组
    SELECT sex FROM readerinfo GROUP BY sex;//查询有多少种性别
    SELECT sex COUNT(*) FROM readerinfo GROUP BY sex;//统计每种性别的人数
    SELECT sex FROM readerinfo GROUP BY sex WHERE COUNT(sex)>3;//也可以加限制条件。统计每种性别的人数
    SELECT * FROM bookinfo ORDER BY price//对查询结果排序,默认为升序
    SELECT * FROM bookinfo ORDER BY price,store;//price相同的,按照库存排序
    SELECT * FROM bookinfo ORDER BY price ASC,store DESC;//asc升序,desc降序
    SELECT * FROM bookinfo LIMIT 3;//limit限制查询数量,偏移量为0开始,显示前三行
    SELECT * FROM bookinfo LIMIT 2,2;//显示第二条语句的后两个语句
    SELECT store,COUNT(*) FROM bookinfo GROUP BY store ORDER BY store DESC LIMIT 4;//统计库存个数,并降序排序,并查看前四条语句

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  • 原文地址:https://www.cnblogs.com/wpbing/p/9196116.html
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