2018-10-29数据库增删改备份统计类界面

查询

• 找出选修多门课程 的学生
  select sno
  from scores
  group by sno
  having count(sno)>1
• 判断不等于最大的分数
  SELECT
  FROM scores
  WHERE degree !=
• 找出最大分数的
  SELECT MAX(degree)
  FROM scores
• 举例:
  -- 找出选修多门课程 的学生
  select sno
  from scores
  group by sno
  having count(sno)>1
  -- 判断不等于最大的分数
  SELECT
  FROM scores
  WHERE degree !=
  -- 找出最大分数的
  SELECT MAX(degree)
  FROM scores
• 举例

select  *

from scores
where degree !=(SELECT  MAX(degree) 
FROM scores) and sno in (SELECT sno
FROM scores
GROUP BY sno
HAVING COUNT(sno)>1)
FROM scores) and sno in (SELECT sno
FROM scores
GROUP BY sno
HAVING COUNT(sno)>1)

• 查询学习课程两门以上的学生信息

• 1.查询学习课程两门
  SELECT
  FROM scores
  GROUP BY sno
  HAVING COUNT(sno)>1;

• 2.学生信息
  SELECT *
  FROM students
  WHERE sno IN(101,107,108,109)

• 查询各个男学生的学习成绩

• 1.查询各个男学生
  SELECT
  FROM students
  WHERE ssex=0;

• 2.的学习成绩
  SELECT degree
  FROM scores
  WHERE sno IN (SELECT sno
  FROM students
  WHERE ssex=0)

• 查询 各个女学生的任课老师姓名,课程名是

• 1.查询 各个女学生的
  SELECT sno
  FROM students
  WHERE ssex=1;

表名(字段名)

• 1.INSERT INTO 表名(字段名1,字段名2)VALUES (字段值1,字段值2)
  2.插入 那里去 表名(1-n个字段,逗号分隔)VALUES(1-n个数据的值)

   INSERT  INTO t_user_user(cst_id,user_name,pwd,STATUS)
VALUES(1145,'guhy666','qweasd',0);

INSERT INTO t_cst_customer(cst_id,cst_name,phone,certNo,province,city,STATUS,sex,email)
VALUES(1175,'顾虹雁','18815123698','695865412154','上海','闵行',0,0,'[email protected]');

INSERT INTO 表名(字段名1,字段名2)VALUES (字段值1,字段值2);
INSERT INTO t_cst_account(account_name,cst_id,balance,STATUS)
VALUES ('guhy','1066','6688',0);

备份(删除,清空)

DELETE FROM 表名;删除全表数据
DELETE FROM 表名 WHERE 条件;删除指定数据
DELETE FROM t_user_user WHERE user_id='8889';

只备份表结构
         CREATE TABLE 临时表名 AS SELECT * FROM  源表名 WHERE 1=2;
只备份表结构+数据
         CREATE TABLE 临时表名 AS SELECT * FROM   源表名 where1-1;
 备份数据
 CREATE TABLE t_user_user_guhy AS SELECT *FROM t_user_user WHERE 1=2;
 CREATE TABLE t_user_user_back1 AS SELECT *FROM t_user_user WHERE 1=1;   
 
 删除表 DROP TABLE 表名;
 DELETE FROM  t_user_user_back1;
 DROP TABLE t_user_user_guhy;
 
 清空表  DELETE FROM 表名;         

数据库增删改备份统计类界面

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聚合函数

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增删改

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表备份

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扩展

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