文章目錄
- mysql單表查詢
- 一、單表查詢文法
- 二、 關鍵字執行的優先級(重點)
- 三、簡單查詢
- 四、單表查詢
- 1、select（篩選列語句）
- 1）select 查詢操作
- 2）distinct 去重操作
- 3）四則運算
- 4）concat和concat_ws(自定義顯示的格式)
- 5）case end 語句
- 6）select的相關總結
- 2、 where （篩選行語句）
- 1） where 概述
- 2）where 查詢的使用
- 3）案列：
- 3、 group by(分組查詢)
- 1）group by概述
- 2）group by 查詢的使用
- 3) group by
- 4、 聚合函數 （count、max、min、avg、sum ）
- 1）常用的聚合函數
- 2）聚合函數的使用
- 3) 案列：
- 5、 having (過濾條件)
- 1）having與where的關系
- 2）having 與where對比
- 3）案列：
- 6、 order by （排序）
- 1）asc與desc（升序與降序）
- 2）排序方式
- 3）案列：
- 7、limit（限制查詢記錄；分頁）
- 1）limit的使用
- 2）案列：
- 8、regexp(正則查詢)
- 1）regexp使用
- 2）案列：
mysql單表查詢
一、單表查詢文法
#基礎格式：
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 二、 關鍵字執行的優先級(重點)
【select查詢語句執行順序詳解URL】
基本流程：
首先執行指令:select —>找到表:from —>拿着指定的限制條件，去檔案/表中取出一條條記錄：where —>将取出的一條條記錄進行分組，如果沒有group by，則整體作為一組：group by —>将分組的結果進行過濾：having —>然後進行去重：distinct —>将結果按條件進行排序：order by —> 最後輸出限制結果的顯示條數:limit
# ！！！重點：(關鍵字的執行優先級)
1:from #找到表
2:where #使用where指定的條件,去表中取出一條條記錄
3:group by #将取出的資料進行分組,如果沒有指定,則整體作為一組
4:having #将分組的結果按照having指定的條件進行過濾
5:select #指定select查詢
6:distinct #去重
7:order by #将查詢的結果按照order by指定的字段進行排序
8:limit #限制結果的顯示數量 三、簡單查詢
#準備表和記錄
company.employee
員工id id int
姓名 emp_name varchar
性别 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
部門編号 depart_id int
#建立表
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
);
#檢視表結構
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，營運
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), #以下是教學部
('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),#以下是銷售部門
('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), #以下是營運部門
('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)
;
#ps：如果在windows系統中，插入中文字元，select的結果為空白，可以将所有字元編碼統一設定成gbk ###########################(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;
#避免重複DISTINCT(去重)
SELECT DISTINCT post FROM employee;
#通過四則運算查詢（運算）
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() #函數用于連接配接字元串
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;
#結合CASE語句：
SELECT
(
CASE
WHEN NAME = 'egon' THEN
NAME
WHEN NAME = 'alex' THEN
CONCAT(name,'_BIGSB')
ELSE
concat(NAME, 'SB')
END
) as new_name
FROM
emp; ###########(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（去掉重複）
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
#查詢以上條件（code編寫）
select concat('<名字:',name,'> ','<薪資:',salary,'>') from employee;
select distinct depart_id from employee;
select name,salary*12 annual_salary from employee; 四、單表查詢
1、select（篩選列語句）
1）select 查詢操作
#注意:所有select 查詢後面右加括号的方法,比如,select user()這種帶括号的都是Mysql的内置方法,select本身就是查詢操作,from隻是說明從哪查
select * from 表名; #查詢表中所有的資料 *代表所有
select 字段名 from 表名; #查詢表中某一個字段的資料
select 字段名,字段名,字段名 from 表名; #查詢表中多個字段的資料
select database(); #查詢傳回目前操作的資料庫
select user(); #查詢目前登陸的使用者
select now; #查詢傳回目前的時間 2）distinct 去重操作
'''
select dictinct 字段名 from 表名;#對查出來的字段資料進行去重
select distinct 字段名,字段名 from 表名;#對多個字段查詢的資料進行聯合去重 3）四則運算
#使用select 查詢某個字段的資料的時候,對數值類型的字段資料,可以進行四則運算,四則運算包括加減乘除等操作
select 字段名*12 from 表名; #對查詢出來的資料乘以12,傳回結果,>>字段名要是數值類型 4）concat和concat_ws(自定義顯示的格式)
concat (字元串拼接)
concat_ws (指定分割符進行拼接)
#concat内置函數可以對查詢出來的字段資料進行字元串拼接
select concat('姓名:',name) from 表名; #對查詢出來的姓名字段的資料前面都加上一個字元串姓名,能夠友好的顯示查詢出來的資料的意思,其實就是字元串拼接
select concat(name,':',salary)as info from 表名; #concat還可以将兩個字段的資料拼接,,産生一個新的字段資料顯示出來,as是個這個字段重命名
concat_ws()函數也隻是字元串拼接,不過concat_ws的憑借方式是類似與python join拼接的方式,就是以某個元素對多個字段的資料進行拼接
select concat_ws('_','姓名:',name,'性别:',sex)as info from 表名; 5）case end 語句
case end 語句對查詢出來的每一個資料進行加工和顯示
#case語句的作用:
對表中資料進行查詢時,對于查詢出來的語句進行進一步的加工,并且顯示出來,case end語句有點像python裡的if語句,不過sql的case語句需要表明開始和結束,case代表開始,end代表束.when代表的就是if條件,else就是其他,當有多個when的時候,從第二個when開始就代表的類似于elif的意思,知道了解就好----->
select(
case
when name='田少崗' concat(name,'逗比')
when name='田彩' concat(name,'女神')
else
concat(name,'邊玩去')
end
)as now_name from 表名; 6）select的相關總結
1>#可以查一個,多個,*所有調用函數： now(),database(),concat(),concat_ws()
2>#可以四則運算
3>#可以去重 distinct
4>#可以使用case end 條件判斷語句 2、 where （篩選行語句）
1） where 概述
1:#範圍查詢
#< > >= <= != <>代表不等于和!=是一個意思
select age from 表名 where age <100 and age>20;(多條件查詢)
#between 1 and 10 找尋1到10之間的
select age from 表名 where between 1 and 100; >>注意包含1和100
#in (1,2,3,4) 多選一
select age from 表名 where age in (10,20,30,40);
#将age=10和age=20的都能取出來
select age from 表名 where age=10 or age=20;
2:#模糊查詢
#like
like的表現形式是:'%a'查詢以a結尾的,'a%'查詢以a開始的,'%a%'查詢包含a的
select name from 表名 where name like '田%';>>> #查詢出姓田的所有人
like還有一種形式,'_a','a_','a__'一個劃線代表一個字元,%代表的是任意長度
select name from 表名 where name 'like '田_';>>> #查詢出以田開頭的兩個字的姓名
(pattern可以是%或_
%表示任意多字元
_表示一個字元)
#regexp 可以使用正則比對(記一下正規表達式)
3:#is is not
is null is not null #一般用來判斷是不是空
4:#邏輯運算: 2）where 查詢的使用
#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不能用等号，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=''; 注意''是空字元串，不是null
ps：
執行
update employee set post_comment='' where id=2;
再用上條檢視，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__'; 3）案列：
#示列：
1. 檢視崗位是teacher的員工姓名、年齡
2. 檢視崗位是teacher且年齡大于30歲的員工姓名、年齡
3. 檢視崗位是teacher且薪資在9000-1000範圍内的員工姓名、年齡、薪資
4. 檢視崗位描述不為NULL的員工資訊
5. 檢視崗位是teacher且薪資是10000或9000或30000的員工姓名、年齡、薪資
6. 檢視崗位是teacher且薪資不是10000或9000或30000的員工姓名、年齡、薪資
7. 檢視崗位是teacher且名字是jin開頭的員工姓名、年薪
#where使用
1》select name,age from employee where post = 'teacher';
2》select name,age from employee where post='teacher' and age > 30;
3》select name,age,salary from employee where post='teacher' and salary between 9000 and 10000;
4》select * from employee where post_comment is not null;
5》select name,age,salary from employee where post='teacher' and salary in (10000,9000,30000);
6》select name,age,salary from employee where post='teacher' and salary not in (10000,9000,30000);
7》select name,salary*12 from employee where post='teacher' and name like 'jin%'; 3、 group by(分組查詢)
1）group by概述
#1、首先明确一點：分組發生在where之後，即分組是基于where之後得到的記錄而進行的
#2、分組指的是：将所有記錄按照某個相同字段進行歸類，比如針對員工資訊表的職位分組，或者按照性别進行分組等
#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： group by：可以對某個字段的值進行分組,這個字段有多少種值就分多少組,group by還有一個特性就是去重,一旦使用group by對資料分組了,就不能對某一條資料進行操作,永遠都是這一組資料
group_concat()函數(隻用來做最終的顯示,不做中間資料的操作)可以顯示目前這一組的所有資訊,拼在一起顯示
select post,group_concat(name),count(id) from employee group by post having count(id) < 2;
'''
###了解即可
mysql> set global sql_mode='STRICT_TRANS_TABLES,ONLY_FULL_GROUP_BY'; 2）group by 查詢的使用
############！！！SQL_MODE設定！！！
#檢視MySQL 5.7預設的sql_mode如下：
mysql> select @@global.sql_mode;
ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
#注意！！！
ONLY_FULL_GROUP_BY的語義就是确定select target list中的所有列的值都是明确語義，簡單的說來，在ONLY_FULL_GROUP_BY模式下，target list中的值要麼是來自于聚集函數的結果，要麼是來自于group by list中的表達式的值。
#設定sql_mole如下操作(我們可以去掉ONLY_FULL_GROUP_BY模式)：
mysql> set global sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION'; mysql> select @@global.sql_mode;
+-------------------+
| @@global.sql_mode |
+-------------------+
| |
+-------------------+
1 row in set (0.00 sec)
mysql> select * from emp group by post;
+----+------+--------+-----+------------+----------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+--------+-----+------------+----------------------------+--------------+------------+--------+-----------+
| 14 | 張野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 |
| 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
| 1 | egon | male | 18 | 2017-03-01 | 老男孩駐沙河辦事處外交大使 | NULL | 7300.33 | 401 | 1 |
+----+------+--------+-----+------------+----------------------------+--------------+------------+--------+-----------+
4 rows in set (0.00 sec)
#由于沒有設定ONLY_FULL_GROUP_BY,于是也可以有結果，預設都是組内的第一條記錄，但其實這是沒有意義的
mysql> set global sql_mode='ONLY_FULL_GROUP_BY';
Query OK, 0 rows affected (0.00 sec)
mysql> quit #設定成功後，一定要退出，然後重新登入方可生效
Bye
mysql> use db1;
Database changed
mysql> select * from emp group by post; #報錯
ERROR 1055 (42000): 'db1.emp.id' isn't in GROUP BY
mysql> select post,count(id) from emp group by post; #隻能檢視分組依據和使用聚合函數
+----------------------------+-----------+
| post | count(id) |
+----------------------------+-----------+
| operation | 5 |
| sale | 5 |
| teacher | 7 |
| 老男孩駐沙河辦事處外交大使 | 1 |
+----------------------------+-----------+
4 rows in set (0.00 sec) 3) group by
如果我們用unique的字段作為分組的依據，則每一條記錄自成一組，這種分組沒有意義,多條記錄之間的某個字段值相同，該字段通常用來作為分組的依據
#單獨使用GROUP BY關鍵字分組
SELECT post FROM employee GROUP BY post;
#注意：我們按照post字段分組，那麼select查詢的字段隻能是post，想要擷取組内的其他相關資訊，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，并檢視組内成員名
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，并檢視每個組有多少人 4、 聚合函數 （count、max、min、avg、sum ）
分組之後:select隻能看到分組字段以及聚合的結果
1）常用的聚合函數
1:#count 計數
2:#max 求最大值
3:#avg 求平均值
4:#min 求最小值
5:#sum 求和 2）聚合函數的使用
#強調：聚合函數聚合的是組的内容，若是沒有分組，則預設一組
#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; 3) 案列：
#示列：
1》查詢崗位名以及崗位包含的所有員工名字
2》查詢崗位名以及各崗位内包含的員工個數
3》查詢公司内男員工和女員工的個數
4》查詢崗位名以及各崗位的平均薪資
5》查詢崗位名以及各崗位的最高薪資
6》查詢崗位名以及各崗位的最低薪資
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
8》查詢出每個部門的員工數
9》查詢男人數與女人數
10》查詢年齡在20歲以上的男人數與女人數
11》查詢每個部門20歲以上人的平均薪資
12》查詢每個部門的平均薪資及最大薪資最小年齡和年齡的和
13》查詢每個部門的員工及年齡
#聚合函數的使用：
#題目1:分組
mysql> select post,group_concat(name) from employee group by post;
+-----------------------------------------+---------------------------------------------------------+
| post | group_concat(name) |
+-----------------------------------------+---------------------------------------------------------+
| operation | 張野,程咬金,程咬銀,程咬銅,程咬鐵 |
| sale | 歪歪,丫丫,丁丁,星星,格格 |
| teacher | alex,wupeiqi,yuanhao,liwenzhou,jingliyang,jinxin,成龍 |
| 老男孩駐沙河辦事處外交大使 | egon |
+-----------------------------------------+---------------------------------------------------------+
#題目2：
mysql> select post,count(id) from employee group by post;
+-----------------------------------------+-----------+
| post | count(id) |
+-----------------------------------------+-----------+
| operation | 5 |
| sale | 5 |
| teacher | 7 |
| 老男孩駐沙河辦事處外交大使 | 1 |
+-----------------------------------------+-----------+
#題目3：
mysql> select sex,count(id) from employee group by sex;
+--------+-----------+
| sex | count(id) |
+--------+-----------+
| male | 10 |
| female | 8 |
+--------+-----------+
#題目4：
mysql> select post,avg(salary) from employee group by post;
+-----------------------------------------+---------------+
| post | avg(salary) |
+-----------------------------------------+---------------+
| operation | 16800.026000 |
| sale | 2600.294000 |
| teacher | 151842.901429 |
| 老男孩駐沙河辦事處外交大使 | 7300.330000 |
+-----------------------------------------+---------------+
#題目5
mysql> select post,max(salary) from employee group by post;
+-----------------------------------------+-------------+
| post | max(salary) |
+-----------------------------------------+-------------+
| operation | 20000.00 |
| sale | 4000.33 |
| teacher | 1000000.31 |
| 老男孩駐沙河辦事處外交大使 | 7300.33 |
+-----------------------------------------+-------------+
#題目6
mysql> select post,min(salary) from employee group by post;
+-----------------------------------------+-------------+
| post | min(salary) |
+-----------------------------------------+-------------+
| operation | 10000.13 |
| sale | 1000.37 |
| teacher | 2100.00 |
| 老男孩駐沙河辦事處外交大使 | 7300.33 |
+-----------------------------------------+-------------+
#題目七
mysql> select sex,avg(salary) from employee group by sex;
+--------+---------------+
| sex | avg(salary) |
+--------+---------------+
| male | 110920.077000 |
| female | 7250.183750 |
+--------+---------------+
#題目八
mysql> select post,count(id) from employee group by post;
#題目九
mysql> select sex,count(id) from employee group by sex;
#題目十
mysql> select sex,count(id) from employee where age > 20 group by sex;
#題十一
mysql> select post,avg(salary) from employee where age > 20 group by post;
#題十二
mysql> select post,avg(salary),max(salary),min(age),count(id),sum(age) from employee group by post;
#題十三
mysql> select post,group_concat(name,":",age) from employee group by post;
+-----------------------------------------+------------------------------------------------------------------------------+
| post | group_concat(name,":",age) |
+-----------------------------------------+------------------------------------------------------------------------------+
| operation | 程咬鐵:18,程咬銅:18,程咬銀:18,程咬金:18,張野:28 |
| sale | 格格:28,星星:18,丁丁:18,丫丫:38,歪歪:48 |
| teacher | 成龍:48,jinxin:18,jingliyang:18,liwenzhou:28,yuanhao:73,wupeiqi:81,alex:78 |
| 老男孩駐沙河辦事處外交大使 | egon:18 |
+-----------------------------------------+------------------------------------------------------------------------------+
4 rows in set (0.00 sec) 5、 having (過濾條件)
having是針對一個組做的過濾條件,是放在group by 後面執行的,他的意思和where是一樣的,where group 和 having的執行順序是:(where—>group by—>having)having一般都是和having一起用的
#示列：
select post,group_concat(name),count(id) from employee group by post having count(id) < 2; 1）having與where的關系
#having與where的之間的不同！！！
！！！執行優先級從高到低：where > group by > 2）having 與where對比
sql_mode:簡而言之就是：它定義了你MySQL應該支援的sql文法，對資料的校驗等等
#select @@sql_mode:使用該指令我們可以檢視我們目前資料庫的sql_mode
mysql> select @@sql_mode;
+--------------------+
| @@sql_mode |
+--------------------+
| ONLY_FULL_GROUP_BY |
+--------------------+
1 row in set (0.00 sec)
mysql> select * from emp where salary > 100000;
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
1 row in set (0.00 sec)
mysql> select * from emp having salary > 100000;
ERROR 1463 (42000): Non-grouping field 'salary' is used in HAVING clause
mysql> select post,group_concat(name) from emp group by post having salary > 10000; #錯誤，分組後無法直接取到salary字段
ERROR 1054 (42S22): Unknown column 'salary' in 'having clause'
mysql> select post,group_concat(name) from emp group by post having avg(salary) > 10000;
+-----------+-------------------------------------------------------+
| post | group_concat(name) |
+-----------+-------------------------------------------------------+
| operation | 程咬鐵,程咬銅,程咬銀,程咬金,張野 |
| teacher | 成龍,jinxin,jingliyang,liwenzhou,yuanhao,wupeiqi,alex |
+-----------+-------------------------------------------------------+
2 rows in set (0.00 sec) 3）案列：
#示列：
1》查詢各崗位内包含的員工個數小于2的崗位名、崗位内包含員工名字、個數
2》查詢各崗位平均薪資大于10000的崗位名、平均工資
3》查詢各崗位平均薪資大于10000且小于20000的崗位名、平均工資
4》查詢出平均薪資在10000以上的部門
5》查出部門内男員工平均工資在3000以上的部門
#題1：
mysql> select post,group_concat(name),count(id) from employee group by post having count(id) < 2;
+-----------------------------------------+--------------------+-----------+
| post | group_concat(name) | count(id) |
+-----------------------------------------+--------------------+-----------+
| 老男孩駐沙河辦事處外交大使 | egon | 1 |
+-----------------------------------------+--------------------+-----------+
#題目2：
mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000;
+-----------+---------------+
| post | avg(salary) |
+-----------+---------------+
| operation | 16800.026000 |
| teacher | 151842.901429 |
+-----------+---------------+
#題目3：
mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 and avg(salary) <20000;
+-----------+--------------+
| post | avg(salary) |
+-----------+--------------+
| operation | 16800.026000 |
+-----------+--------------+
#題目4：
mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000;
+-----------+---------------+
| post | avg(salary) |
+-----------+---------------+
| operation | 16800.026000 |
| teacher | 151842.901429 |
+-----------+---------------+
2 rows in set (0.00 sec)
#題目5:
mysql> select post,avg(salary) from employee where sex="male" group by post
having avg(salary) > 3000;
+-----------------------------------------+---------------+
| post | avg(salary) |
+-----------------------------------------+---------------+
| operation | 16000.043333 |
| teacher | 175650.051667 |
| 老男孩駐沙河辦事處外交大使 | 7300.330000 |
+-----------------------------------------+---------------+
3 rows in set (0.00 sec) 6、 order by （排序）
1）asc與desc（升序與降序）
; #預設不寫，就是升序排列
SELECT * FROM employee ORDER BY salary ASC; #升序
SELECT * FROM employee ORDER BY salary DESC; #降序 2）排序方式
#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; 3）案列：
#示列：
1》查詢所有員工資訊，先按照age升序排序，如果age相同則按照hire_date降序排序
2》查詢各崗位平均薪資大于10000的崗位名、平均工資,結果按平均薪資升序排列
3》查詢各崗位平均薪資大于10000的崗位名、平均工資,結果按平均薪資降序排列
4》查詢所有員工資訊，按照年齡進行升序排列
5》查詢所有員工資訊，按照年齡進行降序排列
6》查詢每個部門薪資大于3000的平均薪資，結果按升序排列
7》查詢所有的員工的年齡按升序排列，id按降序排列
#題目1
mysql> select * from employee ORDER BY age asc,hire_date desc;
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| 1 | egon | male | 18 | 2017-03-01 | 老男孩駐沙河辦事處外交大使 | NULL | 7300.33 | 401 | 1 |
| 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 17 | 程咬銅 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 |
| 18 | 程咬鐵 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
| 16 | 程咬銀 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
| 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 14 | 張野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 |
| 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 8 | 成龍 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
| 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
18 rows in set (0.00 sec)
#題目2
mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 order by avg(salary) asc;
+-----------+---------------+
| post | avg(salary) |
+-----------+---------------+
| operation | 16800.026000 |
| teacher | 151842.901429 |
+-----------+---------------+
#題目3
mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 order by avg(salary) desc;
+-----------+---------------+
| post | avg(salary) |
+-----------+---------------+
| teacher | 151842.901429 |
| operation | 16800.026000 |
+-----------+---------------+
#題目4：
mysql> select * from employee order by age asc;
#題目5：
mysql> select * from employee order by age desc;
#題目6：
mysql> select post,avg(salary) from employee where sex="male" group by post
having avg(salary) > 3000
order by avg(salary);
#題目7：
mysql> select * from employee order by age asc,id desc; 7、limit（限制查詢記錄；分頁）
1）limit的使用
#預設初始位置為0,從第一條開始順序取出三條
SELECT * FROM employee ORDER BY salary DESC LIMIT 3; #排序後限制顯示的行數
#從第0開始，即先查詢出第一條，然後包含這一條在内往後查5條
SELECT * FROM employee ORDER BY salary DESC
LIMIT 0,5; #排序後指定顯示的行數
##從第5開始，即先查詢出第6條，然後包含這一條在内往後查5條
SELECT * FROM employee ORDER BY salary DESC
LIMIT 5,5; 2）案列：
1》分頁顯示，每頁5條
#從第一條開始，每頁顯示5條
mysql> select * from employee limit 0,5;
+----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| 1 | egon | male | 18 | 2017-03-01 | 老男孩駐沙河辦事處外交大使 | NULL | 7300.33 | 401 | 1 |
| 2 | alex | male | 78 | 2015-03-02 | teacher | | 1000000.31 | 401 | 1 |
| 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
+----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
5 rows in set (0.00 sec)
#從第5條開始，每頁顯示5條
mysql> select * from employee limit 5,5;
+----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------------+--------+-----+-------+---------+--------------+----------+--------+-----------+
| 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
| 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 8 | 成龍 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
+----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+
5 rows in set (0.00 sec)
#從第10條開始，每頁顯示5條
mysql> select * from employee limit 10,5;
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 14 | 張野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 |
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
5 rows in set (0.00 sec)
#使用limit取出薪資最高的員工
mysql> select * from employee order by salary desc limit 1;
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
1 row in set (0.00 sec) 8、regexp(正則查詢)
1）regexp使用
#查詢name裡以ale開頭的名字
SELECT * FROM employee WHERE name REGEXP '^ale';
#查詢name裡以xin結尾的名字
select * from employee where name regexp "xin$";
#查詢name裡包含兩個mm的名字
SELECT * FROM employee WHERE name REGEXP 'm{2}';
小結：對字元串比對的方式
WHERE name = 'egon';
WHERE name LIKE 'yua%';
WHERE name REGEXP 'on$'; 2）案列：
1》檢視所有員工中名字是jin開頭，n或者g結果的員工資訊
2》查詢所有員工名字是程開頭的，金鐵結尾的員工資訊
#使用regexp查詢
mysql> select * from employee where name regexp '^jin.*[gn]$';
mysql> select * from employee where name regexp "^程.*[金鐵]$";
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 18 | 程咬鐵 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
2 rows in set (0.00 sec) ![mysql使用source指令導入.sql檔案[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)