SQL学习（时间，存储过程，触发器）

SQL学习

---

1. 几个操作时间的函数

    --datapart 获取时间中的年月日时分秒等部分
    select DATEPART(year,current_timestamp);
    select DATEPART(DAY,current_timestamp);
    select DATEPART(MONTH,current_timestamp);
    
    --dateadd 在相应时间上加上年月日时分秒等
    select CURRENT_TIMESTAMP,DATEADD(DAY,10,CURRENT_TIMESTAMP);
    select DATEADD(month,11,'2001-2-28 12:00:00') as 上帝时刻;
    
    --datediff 获取两时间段的差值并换算为时分秒年月日等
    select DATEDIFF(month,'2014-8-3','2015-9-10');
    
    --转换函数 转换类型
    --cast   convert
    
    select ''+456;
    select ''+cast(456 as varchar);
    select ''+CONVERT(varchar,456);
    
    --convert时间类型转换 后面的数字即不同地区的时间表示方式
    select CURRENT_TIMESTAMP,
    CONVERT(VARCHAR,CURRENT_TIMESTAMP,111);--中国时间表示
    
    select CURRENT_TIMESTAMP,
    CONVERT(VARCHAR,CURRENT_TIMESTAMP,110);--美国时间表示

   ---

2. 简单练习

    --练习题
    use TextDB
    create table TB_CallRecord
    (
    Id int not null identity(1,1),
    CallNumber nvarchar(50),
    TelNum varchar(50),
    StartDateTime datetime null,
    EndDateTime datetime null
    )
    --主键约束
    alter table TB_CallRecord
    add constraint PK_CallRecord primary key (Id);
    --检查约束
    alter table TB_CallRecord
    add constraint CK_CallRecords check(CallNumber like '[0-9][0-9][0-9]')
    
    alter table TB_CallRecord
    add constraint CK_CallRecords_EndDateTime check(EndDateTime > StartDateTime)
    
    --默认约束
    alter table TB_CallRecord
    add constraint DF_CallRecords default(getdate()) for EndDateTime
    
    INSERT TB_CallRecord ([CallNumber], [TelNum], [StartDateTime], [EndDateTime]) VALUES ('', '', CAST(0x00009DAF00A4CB80 AS DateTime), CAST(0x00009DAF00A62E94 AS DateTime));
    INSERT TB_CallRecord ([CallNumber], [TelNum], [StartDateTime], [EndDateTime]) VALUES ('', '', CAST(0x00009DB000D63BC0 AS DateTime), CAST(0x00009DB000D68DC8 AS DateTime));
    INSERT TB_CallRecord ([CallNumber], [TelNum], [StartDateTime], [EndDateTime]) VALUES ('', '', CAST(0x00009DB000E85C60 AS DateTime), CAST(0x00009DB000E92F50 AS DateTime));
    INSERT TB_CallRecord ([CallNumber], [TelNum], [StartDateTime], [EndDateTime]) VALUES ('', '', CAST(0x00009DB2015BB7A0 AS DateTime), CAST(0x00009DB2015C4DA0 AS DateTime));
    INSERT TB_CallRecord ([CallNumber], [TelNum], [StartDateTime], [EndDateTime]) VALUES ('', '', CAST(0x00009DA4014C9C70 AS DateTime), CAST(0x00009DA4014E0308 AS DateTime));
    INSERT TB_CallRecord ([CallNumber], [TelNum], [StartDateTime], [EndDateTime]) VALUES ('', '', CAST(0x00009DB400DAA0C0 AS DateTime), CAST(0x00009DB400DD5FE0 AS DateTime));
    INSERT TB_CallRecord ([CallNumber], [TelNum], [StartDateTime], [EndDateTime]) VALUES ('', '', CAST(0x00009DB200B9AB40 AS DateTime), CAST(0x00009DB200B9FC1C AS DateTime));
    INSERT TB_CallRecord ([CallNumber], [TelNum], [StartDateTime], [EndDateTime]) VALUES ('', '', CAST(0x00009DB8014042B8 AS DateTime), CAST(0x00009DB80141804C AS DateTime));
    INSERT TB_CallRecord ([CallNumber], [TelNum], [StartDateTime], [EndDateTime]) VALUES ('', '', CAST(0x00009D9A00FB9898 AS DateTime), CAST(0x00009D9A00FE6118 AS DateTime));
    INSERT TB_CallRecord ([CallNumber], [TelNum], [StartDateTime], [EndDateTime]) VALUES ('', '', CAST(0x00009D9A00FB9898 AS DateTime), CAST(0x00009D9A00FE6118 AS DateTime));
    
    --查看全表
    select * from TB_CallRecord;
    
    --输出通话时间最长的五条记录
    select top 5 *,DATEDIFF(SECOND,StartDateTime,EndDateTime) as 通话时长 from TB_CallRecord order by DATEDIFF(SECOND,StartDateTime,EndDateTime) DESC; 
    
    --输出所有数据中拨打长途号码（对方号码以0开头）的总时长。like、sum
    SELECT SUM(DATEDIFF(SECOND,StartDateTime,EndDateTime)) from TB_CallRecord WHERE TelNum like '0%';
    
    --输出通话总时长最多的前三个呼叫员的编号。
    select top 3 Id,DATEDIFF(SECOND,StartDateTime,EndDateTime) as 通话时长 from TB_CallRecord order by DATEDIFF(SECOND,StartDateTime,EndDateTime) DESC; 
    
    --输出本月拨打电话次数最多的前三个呼叫员的编号.group by,count(*)
    select top 3 CallNumber,Id,StartDateTime From TB_CallRecord where DATEPART(MONTH,StartDateTime) = 7 order by CallNumber DESC;
    
    --表序列化row_number()over(order by 字段)  就是将不连续的表依据某一列值排序
    select ROW_NUMBER()over(order by Id) as 序列化 ,*from TB_CallRecord;

   ---

3. 事务

    --事务：SQL中每一条语句都是一个事务，任何错误都会导致整个事务失败
   　　--语法：
      /*
   　　begin transaction
   　　  代码
      end
      */
    begin transaction
    declare @myError int;
    update TextDB..TB_CallRecord set CallNumber = 0127897789 where CallNumber = '';
    set @myError = (select @@ERROR);
    update TextDB..TB_CallRecord set CallNumber = ''  where Id = 10;
    set @myError += (select @@ERROR);
    if(@myError!=0)
    begin
    rollback transaction  --回滚当前的操作
    end
    else
    begin
    commit transaction    --执行当前的操作
    end
    --事务的特征：如果一个事务满足原子性，持久性，隔离性，一致性，那么这个操作则称为事务。
    
    --begin transaction
    
    select *from TextDB..TB_CallRecord;

   ---

4. 存储过程

    --存储过程
    --语法：
    /*
        create proc[edure] 存储过程名字
        参数 as 类型 [默认值|out]
        as
        begin
            代码
        end
    */
    --例如：
    go
    create proc usp_text
    as
    begin
    begin transaction
        declare @myError int;
        update TextDB..TB_CallRecord set CallNumber = '' where CallNumber = '';
        set @myError = (select @@ERROR);
        update TextDB..TB_CallRecord set CallNumber = ''  where Id = 10;
        set @myError += (select @@ERROR);
        if(@myError!=0)
    begin
        rollback transaction
    end
        else
    begin
        commit transaction
    end
    
    end
    --执行存储过程
    exec usp_text;
    
    select * from TextDB..TB_CallRecord;
    
    --带参数的存储过程
    go
    create proc usp_text2
    @oldnum as nvarchar(50)
    ,@newnum as nvarchar(50)
    as
    begin
        update TextDB..TB_CallRecord set CallNumber = @newnum where CallNumber = @oldnum;
    end
    
    --调用带参数的存储过程
    exec usp_text2 '','';
    select * from TextDB..TB_CallRecord
    
    --带参数和返回值的存储过程
    go
    create proc usp_text3
    @oldnum as nvarchar(50)
    ,@newnum as nvarchar(50)
    ,@isSuccess int output   --使用output将函数内参数抛出给外部
    as
    begin
        declare @myError int
            update TextDB..TB_CallRecord set CallNumber = @newnum where CallNumber = @oldnum;
            set @myError = (select @@ERROR);
        if(@myError=0)
        begin
            commit
            set @isSuccess = 1
        end
        else
        begin
            rollback
            set @isSuccess = 0;
        end
    end
    
    --调用带参数和返回值的存储过
    declare @result int
    exec usp_text3 '','',@result output;
    select @result; 
    
    --使用try catch
    go
    create proc usp_text4
    @oldnum as nvarchar(50)
    ,@newnum as nvarchar(50)
    ,@IsSucess  int output
    as
    begin
        begin transaction
        update TextDB..TB_CallRecord
        set CallNumber = @newnum
        where CallNumber = @oldnum
        begin try
            commit
            set @IsSucess = 1;
        end try
        begin catch
            rollback
            set @IsSucess = 0;
        end catch
    end
    
    --调用带有try，catch的存储过程
    declare @result int
    exec usp_text4 '','',@result output;
    select @result;

   ---

5. 触发器

    --触发器
    --语法
    /*
    create trigger tr_类型触发器名字 on 表名
    触发类型：after|instea of
    操作类型：inser|delete|update
    as
    begin
        代码
    end
    */
    
    --案例
    --插入数据的同时获得自动增长的Id
    select * from TextDB..TB_USER;
    
    insert INTO TextDB..TB_USER (userID,[password],code,lastTime)
    OUTPUT inserted.userID
    VALUES ('aaa','DDD','','2007-03-12');
    
    -----------
    go
    create trigger tr_delete_不会删除的表 on TextDB..TB_USER
    after
    delete
    as
         insert into TextDB..TB_USER(userID,[password],code,lastTime)
         select userID,[password],code,lastTime from deleted;
    go
    
    select * from TextDB..TB_USER;
    delete TB_USER
    select SUSER_NAME();

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