From babda1104d6cc59f966e7036a581360de605eab7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=99=86=E5=88=A9=E7=BE=A4?= <2246026162@qq.com>
Date: Sun, 18 Sep 2022 11:15:21 +0000
Subject: [PATCH] =?UTF-8?q?=E9=99=86=E5=88=A9=E7=BE=A4?=
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit

Signed-off-by: 陆利群 <2246026162@qq.com>
---
 .../9.18\347\254\224\350\256\260.md"          | 85 +++++++++++++++++++
 ...4\346\254\241\344\275\234\344\270\232.sql" | 56 ++++++++++++
 2 files changed, 141 insertions(+)
 create mode 100644 "32\351\231\206\345\210\251\347\276\244/9.18\347\254\224\350\256\260.md"
 create mode 100644 "32\351\231\206\345\210\251\347\276\244/9.18\347\254\254\344\272\214\346\254\241\344\275\234\344\270\232.sql"

diff --git "a/32\351\231\206\345\210\251\347\276\244/9.18\347\254\224\350\256\260.md" "b/32\351\231\206\345\210\251\347\276\244/9.18\347\254\224\350\256\260.md"
new file mode 100644
index 0000000..bdfa83b
--- /dev/null
+++ "b/32\351\231\206\345\210\251\347\276\244/9.18\347\254\224\350\256\260.md"
@@ -0,0 +1,85 @@
+ 主键：primary key
+
+自增：indentity（x,y）[从x开始每次增加y]
+
+非空：not null
+
+默认：default（）
+
+ check约束：chenk（条件）
+
+唯一：unique
+
+外键：(foreign key)references 表名（字段名）
+
+外键：Alter table 表名 add constraint 约束名 foreign key(字段名) references 主键表(字段)
+
+增加字段：Alter table 表名 add 字段名 条件
+
+
+
+SQL语句执行顺序:
+
+1.FROM <left_table>
+
+2.ON <join_condition>
+
+3.<join_type> **JOIN** <right_table>
+
+4.**WHERE** <where_condition>
+
+5.**GROUP** **BY** <group_by_list>
+
+6. HAVING <having_condition>
+
+7.**SELECT** 
+
+8.**DISTINCT** <select_list>
+
+9.**ORDER** **BY** <order_by_condition>
+
+10.**LIMIT** <limit_number>
+
+
+
+聚合函数：
+
+1.count:求数量
+
+2.**max**:求最大值
+
+3.**min**:求最小值
+
+4.**sum**:求和
+
+5.**avg**:求平均值
+
+
+
+sql中常用的时间函数：
+
+**select** DATEDIFF(**day**, '2019-08-20', getDate());    --获取指定时间单位的差值
+
+**SELECT** DATEADD(**MINUTE**,-5,GETDATE())               --加减时间,此处为获取五分钟前的时间,MINUTE 表示分钟，可为 YEAR,MONTH,DAY,HOUR
+
+**select** DATENAME(**month**, getDate());                --当前月份
+
+**select** DATENAME(WEEKDAY, getDate());              --当前星期几
+
+**select** DATEPART(**month**, getDate());                --当前月份
+
+**select** **DAY**(getDate());                            --返回当前日期天数
+
+**select** **MONTH**(getDate());                          --返回当前日期月数
+
+**select** YEAR(getDate());                           --返回当前日期年数
+
+**SELECT** **CONVERT**(VARCHAR(22),GETDATE(),20)          --2020-01-09 14:46:46
+
+**SELECT** **CONVERT**(VARCHAR(24),GETDATE(),21)          --2020-01-09 14:46:55.91
+
+**SELECT** **CONVERT**(VARCHAR(22),GETDATE(),23)		  --2020-01-09
+
+**SELECT** **CONVERT**(VARCHAR(22),GETDATE(),24)          --15:04:07
+
+**Select** **CONVERT**(varchar(20),GETDATE(),14)          --15:05:49:330
diff --git "a/32\351\231\206\345\210\251\347\276\244/9.18\347\254\254\344\272\214\346\254\241\344\275\234\344\270\232.sql" "b/32\351\231\206\345\210\251\347\276\244/9.18\347\254\254\344\272\214\346\254\241\344\275\234\344\270\232.sql"
new file mode 100644
index 0000000..d1d374c
--- /dev/null
+++ "b/32\351\231\206\345\210\251\347\276\244/9.18\347\254\254\344\272\214\346\254\241\344\275\234\344\270\232.sql"
@@ -0,0 +1,56 @@
+select * from Department
+select * from [Rank]
+select * from People 
+
+--1. ��ѯ���人�������е�Ա����Ϣ��Ҫ����ʾ���������Լ�Ա������ϸ����
+select p.*,d.DepartmentName from People p 
+join Department d on d.DepartmentId=p.DepartmentId
+where PeopleAddress='�人'
+
+
+--2. ��ѯ���人�������е�Ա����Ϣ��Ҫ����ʾ�������ƣ�ְ�������Լ�Ա������ϸ����
+select p.*,d.DepartmentName,r.RankName from People p
+join Department d on d.DepartmentId=p.DepartmentId
+join Rank r on r.RankId=p.RankId
+where PeopleAddress='�人'
+
+--3. ���ݲ��ŷ���ͳ��Ա��������Ա�������ܺͣ�ƽ�����ʣ���߹��ʺ���͹��ʡ�
+select DepartmentId,COUNT(*)Ա������,SUM(PeopleSalary)Ա�������ܺ�,
+AVG(PeopleSalary)ƽ������,MAX(PeopleSalary)��߹���,MIN(PeopleSalary)��͹��� from People
+group by DepartmentId
+
+--4. ���ݲ��ŷ���ͳ��Ա��������Ա�������ܺͣ�ƽ�����ʣ���߹��ʺ���͹��ʣ�
+--ƽ��������10000 ���µIJ�����ͳ�ƣ����Ҹ���ƽ�����ʽ������С�
+select DepartmentId,COUNT(*)Ա������,SUM(PeopleSalary)Ա�������ܺ�,
+AVG(PeopleSalary)ƽ������,MAX(PeopleSalary)��߹���,MIN(PeopleSalary)��͹��� from People
+group by DepartmentId
+having AVG(PeopleSalary)>=10000
+order by ƽ������ desc
+
+--5. ���ݲ������ƣ�Ȼ�����ְλ���ƣ�����ͳ��Ա��������Ա�������ܺͣ�ƽ�����ʣ���߹��ʺ���͹���
+select d.DepartmentName ,COUNT(*) Ա������,SUM(PeopleSalary) Ա�������ܺ� ,
+AVG(PeopleSalary) ƽ������,MAX(PeopleSalary) ��߹���,MIN(PeopleSalary) ��͹��� from People p
+join Department  d on d.DepartmentId=p.DepartmentId
+group by d.DepartmentName,RankId
+
+--6.��ѯ����з 6.22--7.22 ��Ա����Ϣ
+select * from People where
+(MONTH(PeopleBirth)=6 and DAY(PeopleBirth)>=22) or
+(MONTH(PeopleBirth)=7 and DAY(PeopleBirth)<=22)
+
+--7.��ѯ����Ա����Ϣ������һ����ʾ����(��,ţ,��,��,��,��,��,��,��,��,��,��)
+select *,case YEAR(PeopleBirth) % 12
+when 4 then '��'
+when 5 then 'ţ'
+when 6 then '��'
+when 7 then '��'
+when 8 then '��'
+when 9 then '��'
+when 10 then '��'
+when 11 then '��'
+when 0 then '��'
+when 1 then '��'
+when 2 then '��'
+when 3 then '��'
+end ����
+ from People
\ No newline at end of file
-- 
Gitee