mysql表操作之數據操作
阿新 • • 發佈:2018-02-15
為什麽 順序 create 多少 平均工資 uniq 單條件 表操作 upd
一、介紹
在MySQL管理軟件中,可以通過SQL語句中的DML語言來實現數據的操作,包括
使用INSERT實現數據的插入
UPDATE實現數據的更新
使用DELETE實現數據的刪除
使用SELECT查詢數據以及。
二、插入數據INSERT
1. 插入完整數據(順序插入) 語法一: INSERT INTO 表名(字段1,字段2,字段3…字段n) VALUES(值1,值2,值3…值n); 語法二: INSERT INTO 表名 VALUES (值1,值2,值3…值n); 2. 指定字段插入數據 語法: INSERT INTO 表名(字段1,字段2,字段3…) VALUES (值1,值2,值3…); 3. 插入多條記錄 語法: INSERT INTO 表名 VALUES (值1,值2,值3…值n), (值1,值2,值3…值n), (值1,值2,值3…值n); 4. **插入查詢結果** 語法: INSERT INTO 表名(字段1,字段2,字段3…字段n) SELECT (字段1,字段2,字段3…字段n) FROM 表2 WHERE …;
三、更新數據UPDATE
語法:
UPDATE 表名 SET
字段1=值1,
字段2=值2 WHERE CONDITION;
示例:
UPDATE mysql.user SET password=password(‘123’)
where user=’root’ and host=’localhost’;
四、刪除數據DELETE
語法:
DELETE FROM 表名
WHERE CONITION;
示例:
DELETE FROM mysql.user
WHERE password= ’’;
練習:
更新MySQL root用戶密碼為mysql123
刪除除從本地登錄的root用戶以外的所有用戶
查詢數據
1. 單表查詢的語法
SELECT 字段1,字段2... FROM 表名
WHERE 條件
GROUP BY field
HAVING 篩選
ORDER BY field
LIMIT 限制條數
2. 關鍵字的執行優先級(重點)
重點中的重點:關鍵字的執行優先級 from where 約束條件 group by 分組 having 過濾 select distinct order by limit
1.找到表:from
2.拿著where指定的約束條件,去文件/表中取出一條條記錄
3.將取出的一條條記錄進行分組group by,如果沒有group by,則整體作為一組
4.將分組的結果進行having過濾
5.執行select
6.去重
7.將結果按條件排序:order by
8.限制結果的顯示條數
準備表和記錄
company.employee
員工id id int
姓名 emp_name varchar
性別 sex enum
年齡 age int
入職日期 hire_date date
崗位 post varchar
職位描述 post_comment varchar
薪水 salary double
辦公室 office int
部門編號 depart_id int
#創建表
create table employee(
id int not null unique auto_increment,
name varchar(20) not null,
sex enum(‘male‘,‘female‘) not null default ‘male‘, #大部分是男的
age int(3) unsigned not null default 28,
hire_date date not null,
post varchar(50),
post_comment varchar(100),
salary double(15,2),
office int, #一個部門一個屋子
depart_id int
);
#查看表結構
mysql> desc employee;
+--------------+-----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-----------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(20) | NO | | NULL | |
| sex | enum(‘male‘,‘female‘) | NO | | male | |
| age | int(3) unsigned | NO | | 28 | |
| hire_date | date | NO | | NULL | |
| post | varchar(50) | YES | | NULL | |
| post_comment | varchar(100) | YES | | NULL | |
| salary | double(15,2) | YES | | NULL | |
| office | int(11) | YES | | NULL | |
| depart_id | int(11) | YES | | NULL | |
+--------------+-----------------------+------+-----+---------+----------------+
#插入記錄
#三個部門:教學,銷售,運營
insert into employee(name,sex,age,hire_date,post,salary,office,depart_id) values
(‘egon‘,‘male‘,18,‘20170301‘,‘老男孩駐沙河辦事處外交大使‘,7300.33,401,1),
(‘alex‘,‘male‘,78,‘20150302‘,‘teacher‘,1000000.31,401,1),
(‘wupeiqi‘,‘male‘,81,‘20130305‘,‘teacher‘,8300,401,1),
(‘yuanhao‘,‘male‘,73,‘20140701‘,‘teacher‘,3500,401,1),
(‘liwenzhou‘,‘male‘,28,‘20121101‘,‘teacher‘,2100,401,1),
(‘jingliyang‘,‘female‘,18,‘20110211‘,‘teacher‘,9000,401,1),
(‘jinxin‘,‘male‘,18,‘19000301‘,‘teacher‘,30000,401,1),
(‘成龍‘,‘male‘,48,‘20101111‘,‘teacher‘,10000,401,1),
(‘歪歪‘,‘female‘,48,‘20150311‘,‘sale‘,3000.13,402,2),
(‘丫丫‘,‘female‘,38,‘20101101‘,‘sale‘,2000.35,402,2),
(‘丁丁‘,‘female‘,18,‘20110312‘,‘sale‘,1000.37,402,2),
(‘星星‘,‘female‘,18,‘20160513‘,‘sale‘,3000.29,402,2),
(‘格格‘,‘female‘,28,‘20170127‘,‘sale‘,4000.33,402,2),
(‘張野‘,‘male‘,28,‘20160311‘,‘operation‘,10000.13,403,3),
(‘程咬金‘,‘male‘,18,‘19970312‘,‘operation‘,20000,403,3),
(‘程咬銀‘,‘female‘,18,‘20130311‘,‘operation‘,19000,403,3),
(‘程咬銅‘,‘male‘,18,‘20150411‘,‘operation‘,18000,403,3),
(‘程咬鐵‘,‘female‘,18,‘20140512‘,‘operation‘,17000,403,3)
;
#簡單查詢
SELECT id,name,sex,age,hire_date,post,post_comment,salary,office,depart_id
FROM employee;
SELECT * FROM employee;
SELECT name,salary FROM employee;
#避免重復DISTINCT
SELECT DISTINCT post FROM employee;
#通過四則運算查詢
SELECT name, salary*12 FROM employee;
SELECT name, salary*12 AS Annual_salary FROM employee;
SELECT name, salary*12 Annual_salary FROM employee;
#定義顯示格式
CONCAT() 函數用於連接字符串
SELECT CONCAT(‘姓名: ‘,name,‘ 年薪: ‘, salary*12) AS Annual_salary
FROM employee;
CONCAT_WS() 第一個參數為分隔符
SELECT CONCAT_WS(‘:‘,name,salary*12) AS Annual_salary
FROM employee;
- 小練習
1 查出所有員工的名字,薪資,格式為 <名字:egon> <薪資:3000> 2 查出所有的崗位(去掉重復) 3 查出所有員工名字,以及他們的年薪,年薪的字段名為annual_year
WHERE約束
where字句中可以使用:
1. 比較運算符:> < >= <= <> !=
2. between 80 and 100 值在10到20之間
3. in(80,90,100) 值是10或20或30
4. like ‘egon%‘
pattern可以是%或_,
%表示任意多字符
_表示一個字符
5. 邏輯運算符:在多個條件直接可以使用邏輯運算符 and or not
#1:單條件查詢
SELECT name FROM employee
WHERE post=‘sale‘;
#2:多條件查詢
SELECT name,salary FROM employee
WHERE post=‘teacher‘ AND salary>10000;
#3:關鍵字BETWEEN AND
SELECT name,salary FROM employee
WHERE salary BETWEEN 10000 AND 20000;
SELECT name,salary FROM employee
WHERE salary NOT BETWEEN 10000 AND 20000;
#4:關鍵字IS NULL(判斷某個字段是否為NULL不能用等號,需要用IS)
SELECT name,post_comment FROM employee
WHERE post_comment IS NULL;
SELECT name,post_comment FROM employee
WHERE post_comment IS NOT NULL;
SELECT name,post_comment FROM employee
WHERE post_comment=‘‘; 註意‘‘是空字符串,不是null
ps:
執行
update employee set post_comment=‘‘ where id=2;
再用上條查看,就會有結果了
#5:關鍵字IN集合查詢
SELECT name,salary FROM employee
WHERE salary=3000 OR salary=3500 OR salary=4000 OR salary=9000 ;
SELECT name,salary FROM employee
WHERE salary IN (3000,3500,4000,9000) ;
SELECT name,salary FROM employee
WHERE salary NOT IN (3000,3500,4000,9000) ;
#6:關鍵字LIKE模糊查詢
通配符’%’
SELECT * FROM employee
WHERE name LIKE ‘eg%‘;
通配符’_’
SELECT * FROM employee
WHERE name LIKE ‘al__‘;
- 小練習
1. 查看崗位是teacher的員工姓名、年齡
2. 查看崗位是teacher且年齡大於30歲的員工姓名、年齡
3. 查看崗位是teacher且薪資在9000-10000範圍內的員工姓名、年齡、薪資
4. 查看崗位描述不為NULL的員工信息
5. 查看崗位是teacher且薪資是10000或9000或30000的員工姓名、年齡、薪資
6. 查看崗位是teacher且薪資不是10000或9000或30000的員工姓名、年齡、薪資
7. 查看崗位是teacher且名字是jin開頭的員工姓名、年薪
分組查詢:GROUP BY
- 什麽是分組?為什麽要分組?
#1、首先明確一點:分組發生在where之後,即分組是基於where之後得到的記錄而進行的
#2、分組指的是:將所有記錄按照某個相同字段進行歸類,比如針對員工信息表的職位分組,或者按照性別進行分組等
#3、為何要分組呢?
取每個部門的最高工資
取每個部門的員工數
取男人數和女人數
小竅門:‘每’這個字後面的字段,就是我們分組的依據
#4、大前提:
可以按照任意字段分組,但是分組完畢後,比如group by post,只能查看post字段,如果想查看組內信息,需要借助於聚合函數
- GROUP_BY
- 先確定分組的條件,然後再利用函數將其他字段的記錄整合成一行即可;
單獨使用GROUP BY關鍵字分組
SELECT post FROM employee GROUP BY post;
註意:我們按照post字段分組,那麽select查詢的字段只能是post,想要獲取組內的其他相關信息,需要借助函數
GROUP BY關鍵字和GROUP_CONCAT()函數一起使用
SELECT post,GROUP_CONCAT(name) FROM employee GROUP BY post;#按照崗位分組,並查看組內成員名
SELECT post,GROUP_CONCAT(name) as emp_members FROM employee GROUP BY post;
GROUP BY與聚合函數一起使用
select post,count(id) as count from employee group by post;#按照崗位分組,並查看每個組有多少人
# 求每個分類的記錄個數
mysql> select depart_id,count(name) from employee group by depart_id;
+-----------+-------------+
| depart_id | count(name) |
+-----------+-------------+
| 1 | 8 |
| 2 | 5 |
| 3 | 5 |
+-----------+-------------+
3 rows in set (0.00 sec)
# 將符合類別的所有記錄的名字組合成一項
mysql> select depart_id, group_concat(name) from employee group by depart_id;
+-----------+------------------------------------------------------------+
| depart_id | group_concat(name) |
+-----------+------------------------------------------------------------+
| 1 | egon,alex,wupeiqi,yuanhao,liwenzhou,jingliyang,jinxin,成龍 |
| 2 | 歪歪,丫丫,丁丁,星星,星星 |
| 3 | 張野,程咬金,程咬銀,程咬銅,程咬鐵 |
+-----------+------------------------------------------------------------+
3 rows in set (0.00 sec)
# 求每個類別中的最大值
mysql> select depart_id, max(salary) from employee group by depart_id;
+-----------+-------------+
| depart_id | max(salary) |
+-----------+-------------+
| 1 | 1000000.31 |
| 2 | 3000.29 |
| 3 | 20000.00 |
+-----------+-------------+
3 rows in set (0.00 sec)
- 聚合函數
#強調:聚合函數聚合的是組的內容,若是沒有分組,則默認一組
示例:
SELECT COUNT(*) FROM employee;
SELECT COUNT(*) FROM employee WHERE depart_id=1;
SELECT MAX(salary) FROM employee;
SELECT MIN(salary) FROM employee;
SELECT AVG(salary) FROM employee;
SELECT SUM(salary) FROM employee;
SELECT SUM(salary) FROM employee WHERE depart_id=3;
- 小練習
1. 查詢崗位名以及崗位包含的所有員工名字
mysql> select post, group_concat(name) from emp group by post;
2. 查詢崗位名以及各崗位內包含的員工個數
mysql> select post, count(id) from emp group by post;
3. 查詢公司內男員工和女員工的個數
mysql> select sex, count(id) from emp group by sex;
4. 查詢崗位名以及各崗位的平均薪資
mysql> select post, avg(salary) as ‘平均薪資‘ from emp group by post;
5. 查詢崗位名以及各崗位的最高薪資
select post, max(salary) as ‘最高薪資‘ from emp group by post;
6. 查詢崗位名以及各崗位的最低薪資
select post, max(salary) as ‘最高薪資‘ from emp group by post;
7. 查詢男員工與男員工的平均薪資,女員工與女員工的平均薪資
select sex, avg(salary) as ‘平均薪資‘ from emp group by sex;
- HAVING過濾
#!!!執行優先級從高到低:where > group by > having
#1. Where 發生在分組group by之前,因而Where中可以有任意字段,但是絕對不能使用聚合函數。
#2. Having發生在分組group by之後,因而Having中可以使用分組的字段,無法直接取到其他字段,可以使用聚合函數
- 小練習
1. 查詢各崗位內包含的員工個數小於2的崗位名、崗位內包含員工名字、個數
select post, group_concat(name) as "員工姓名", count(id) as "員工數量" from emp group by post having count(id) <2;
3. 查詢各崗位平均薪資大於10000的崗位名、平均工資
select post, avg(salary) from emp group by post having avg(salary)>10000 ;
4. 查詢各崗位平均薪資大於10000且小於20000的崗位名、平均工資
select post, avg(salary) from emp group by post;select post, avg(salary) from emp group by post having avg(salary) in (10000, 20000) ;
- 查詢排序:ORDER BY
按單列排序
SELECT * FROM employee ORDER BY salary;
SELECT * FROM employee ORDER BY salary ASC;
SELECT * FROM employee ORDER BY salary DESC;
按多列排序:先按照age排序,如果年紀相同,則按照薪資排序
SELECT * from employee
ORDER BY age,
salary DESC;
- 小練習
1. 查詢所有員工信息,先按照age升序排序,如果age相同則按照hire_date降序排序
select * from emp order by age desc, hire_date desc;
2. 查詢各崗位平均薪資大於10000的崗位名、平均工資,結果按平均薪資升序排列
# 1.對post進行分組;2.having篩選工資;3.工資排序;
select post, avg(salary) as ‘平均工資‘ from emp group by post having avg(salary)>10000 order by avg(salary);
3. 查詢各崗位平均薪資大於10000的崗位名、平均工資,結果按平均薪資降序排列
- 限制查詢的記錄數:LIMIT
示例:
SELECT * FROM employee ORDER BY salary DESC
LIMIT 3; #默認初始位置為0
SELECT * FROM employee ORDER BY salary DESC
LIMIT 0,5; #從第0開始,即先查詢出第一條,然後包含這一條在內往後查5條
SELECT * FROM employee ORDER BY salary DESC
LIMIT 5,5; #從第5開始,即先查詢出第6條,然後包含這一條在內往後查5條
- 小練習
1. 分頁顯示,每頁5條
select * from emp limit 5;
select * from emp limit 5, 5;
select * from emp limit 10, 5;
- 使用正則表達式查詢
SELECT * FROM employee WHERE name REGEXP ‘^ale‘;
SELECT * FROM employee WHERE name REGEXP ‘on$‘;
SELECT * FROM employee WHERE name REGEXP ‘m{2}‘;
小結:對字符串匹配的方式
WHERE name = ‘egon‘; # 準確查詢
WHERE name LIKE ‘yua%‘; # 模糊查詢
WHERE name REGEXP ‘on$‘; # 模糊查詢
- 小練習
查看所有員工中名字是jin開頭,n或者g結果的員工信息
select * from emp where name regexp "^jin.*[ng]$";
mysql表操作之數據操作