步步为营-35-SQL语言基础

SQL 结构化查询语言(Structured Query Language)

DDL DML DCL 在此不再对其进行详细解释

1 DDL 数据库定义语言

　　1.1 创建数据库脚本　　

　　

--DDL create drop alter
--创建数据库
create database TestDB;
--删除数据库
drop database TestDB;

--创建数据库
create database DemoDB2
on
(
    name = 'DemoDB2',--逻辑名称于创建名字一致
    size = 5MB,        --最小为5MB
    filegrowth = 2MB,--超过5MB后以步长为2MB增长
    fileName = 'F:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\DemoDB2.mdf' -- 文件存放路径
)
log on
(
    name = 'DemoDB2_log',
    size = 2MB,        --最小为2MB
    filegrowth = 2MB,--超过5MB后以步长为2MB增长
    fileName = 'F:\Program Files\Microsoft SQL Server\MSSQL12.MSSQLSERVER\MSSQL\DATA\DemoDB2_log.ldf' 

)

创建数据库

　　1.2 操作表脚本　

　　

use DemoDB
go
--1创建表
Create table Employee
(
    --设置自增长主键,不为空
    EmpId int identity(,) primary key not null,
    EmpName nvarchar() null,--定义大小为2的幂 ,
    EmpAge int default() not null, -- 设置默认值18
    Delflag smallint default() not null
)
go
--2修改表
    --2.1 修改表名称
    --ALTER TABLE DemoDB.Employee rename to DemoDB.Student;--不好使
    --通过存储过程重新命名
    exec sp_rename 'Employee','Student'
    --2.2 修改列
        --2.2. 修改列名
        exec sp_rename 'Student.EmpAge','StuAge'
        --2.2. 新增列
        Alter table Student add StuClassNo int
        --2.2. 修改列
        Alter table Student alter column StuClassNo nvarchar()
        --2.2. 删除列
        Alter table Student  drop column StuClassNo
--3删除表
drop table UserInfo

2 DML 数据库操作语言(很重要)
　　2.1 Select 语句都被写烂了,这里总结一下执行顺序

　　From=>where=>group by =>having=>select=>order by　　

　　

--Insert into 表名(列名称...) values (值..);
Insert into  Student (EmpId, StuName, StuAge, Delflag) values (,'张三',,);
--删除
delete from Student where =

--查询
select *  from Student;
--修改 Update 表名 set 列名 = 值 where 条件表达式
Update Student set StuName = '李四' where EmpId = ;

　　2.2 约束:保证数据的完整性

　　　　alter table 表名 add constraint 约束的名字.....　　　　

　　

-- 删除约束
    --alter table 表名 drop constraint 约束的名字
    alter table UserInfo drop constraint DF_UserInfo_DelFlag
--  添加默认约束
    　--alter table 表名 add constraint 约束的名字 default() for ...
    　 alter table UserInfo add constraint DF_UserInfo_DelFlag default() for DelFlag;
-- 添加主键约束
        alter table UserInfo add constraint PK_UserInfo_EmpId primary key(EmpId);
-- 添加唯一约束
        alter table UserInfo add constraint UN_UserInfo_StuName unique (StuName)
-- 添加检查约束
        alter table UserInfo add constraint CK_UserInfo_StuAge check(StuAge> and StuAge<)
-- 非空约束
        --以便建表的时候就创建了
-- 外键约束
        -- 先建立外键表Class
        create table ClassInfo
        (
            ClassId int identity(,) primary key,
            ClassName nvarchar() null
        )
        -- 添加外键列
        alter table UserInfo add ClassNo int null
        -- 添加外键约束
        alter table UserInfo add constraint FK_UserInfo_ClassInfo  foreign key(ClassNO) references ClassInfo(ClassId);

约束

　　2.3 常用的函数　　

　　

use DemoDB
go

select * from UserInfo
-- 给列和表起别名
select EmpId as 编号 from UserInfo as U;
--count()优于count(*);因为count(*) 找出表中最短的数列
--常见的聚合函数
--count(),sum(),max(),min(),avg(),max(),min()
--常见的转换函数
--Convert(目标类型,转换的表达式,格式规范)
--Cast(表达式 as 类型)
select StuName+'年龄是'+CONVERT(nvarchar(),StuAge) as 学生年龄信息 from UserInfo;
select StuName+'年龄是'+Cast(StuAge as nvarchar()) as 学生年龄信息 from UserInfo;
--日期函数
    --01获取当前日期
    --select getdate();
    --dateadd(要增加的计量单位,数量,原有日期)添加日期
    select DATEADD(day,,'2012-12-12')
    -- DATEDIFF(要比较的计量单位,日期,日期)时间差
    select DATEDIFF(DAY,'2012-12-12','2012-12-19');
    --DatePart
    select DATEPART(MONTH,'2014-1-15');
    select MONTH('2014-1-15');
--字符串函数
    --转换大(upper)小(LOWER)写
    select Upper('abc') ;
    --字符串左(left)右(right)截取
    select left('',);
    --字符串长度
    select DATALENGTH(N'');
    --去掉左(LTRIM)右(RTRIM)空格
    select LTRIM('   1231   ');

常用的函数

　　2.4 Case When的两种使用

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace 完整的增删查改
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void MainForm_Load(object sender, EventArgs e)
        {
            string sqlStr = "select EmpId, Pwd, StuName, StuAge, Delflag, ClassNo from UserInfo where Delflag = 0 ";

            LoadUserInfoToGridView(sqlStr);
        }
        //获取连接字符串
       public string ConnStr = SqlHelper.GetConnStr();

        #region 02右击删除-多项删除
        private void contextMenuDelete_Opening(object sender, CancelEventArgs e)
        {
            //02-01给出提示,判断是否确定删除
            if (MessageBox.Show("确认删除选中信息吗?","提示信息",MessageBoxButtons.YesNo,MessageBoxIcon.Information) != DialogResult.Yes)
            {
                return;
            }
            //02-02 拿到选中行的主键,并把主键拼接起来
            var rows = this.dataGridView1.SelectedRows;
            //02-03 编写执行SQL脚本

            #region 方法二-

            StringBuilder sbSql = new StringBuilder();
             List<SqlParameter> parameters = new List<SqlParameter>( );
            for (int i = ; i < rows.Count; i++)
            {
                sbSql.Append("Update UserInfo set DelFlag = 1 where EmpId=@EmpId"+i+";");
                SqlParameter para = new SqlParameter("@EmpId"+i,SqlDbType.Int);
                para.Value = int.Parse(rows[i].Cells["EmpId"].Value.ToString());
                parameters.Add(para);

            }
            string sqlStr2 = sbSql.ToString();
            #endregion

            int resultNum = SqlHelper.ExcuteNonQuery(sqlStr2, parameters.ToArray());
            if (resultNum > )
            {
                MessageBox.Show("删除成功!一共删除" + resultNum + "条");
            }

            MainForm_Load(this,null);
        }
        #endregion

        #region 03双击事件-弹出修改窗体
        private void dataGridView1_CellDoubleClick(object sender, DataGridViewCellEventArgs e)
        {
            //03-01 拿到Id
            int id = int.Parse(dataGridView1.SelectedRows[].Cells["EmpId"].Value.ToString());

            //03-02打开修改窗体
            EditForm frmEdit = new EditForm(new UserInfo (){EmpId = id});
            //03-04让主窗体关注"编辑窗体"的关闭事件.
            frmEdit.FormClosing += EditUserInfoFrm_FormClosing;
            frmEdit.Show();
            //03-03 通过构造函数传递数据
        }
        //03-04 当修改窗体关闭时候执行下面的事件响应方法
        private void EditUserInfoFrm_FormClosing(object sender, FormClosingEventArgs e)
        {
            btnSearch_Click(this, null);
        }
        #endregion

        #region 04-多条件查询
        private void btnSearch_Click(object sender, EventArgs e)
        {
            //string connStr = SqlHelper.GetConnStr();
            #region 04-02拼接SQl语句
            string sqlText = "select  EmpId, Pwd, StuName, StuAge, Delflag, ClassNo from UserInfo";
            List<string> whereList = new List<string>();
            List<SqlParameter> parameters = new List<SqlParameter>();

            if (!string.IsNullOrEmpty(this.txtName.Text.Trim()))
            {
                //把Where条件添加到List集合中
                whereList.Add(" StuName like @StuName ");
                //把参数进行赋值
                SqlParameter parameter = new SqlParameter();
                parameter.ParameterName = "@StuName";
                parameter.Value = "%" + txtName.Text + "%";
                parameters.Add(parameter);
            }

            if (!string.IsNullOrEmpty(this.txtAge.Text.Trim()))
            {
                //把Where条件添加到List集合中
                whereList.Add(" StuAge like @StuAge ");
                //把参数进行赋值
                SqlParameter parameter = new SqlParameter();
                parameter.ParameterName = "@StuAge";
                parameter.Value = "%" + txtAge.Text + "%";
                parameters.Add(parameter);
            }

            if (whereList.Count > )
            {
                sqlText += " where " + string.Join(" and ", whereList);
            }
            #endregion
            LoadUserInfoToGridView(sqlText, parameters.ToArray());

        }
        #endregion

        #region 05-将01和04进行优化可得-----加载数据到GridView
        private void LoadUserInfoToGridView(string sqlStr,params SqlParameter[] parameters)
        {
            //01-00 设置强类型数据源
            List<UserInfo> userInfoList = new List<UserInfo>();
            DataTable dt = SqlHelper.ExcuteDataTable(sqlStr, parameters);
            //01-05 应该使用强类型数据
            foreach (DataRow dr in dt.Rows)
            {
                //数据封装
                UserInfo userInfo = new UserInfo();
                userInfo.EmpId = int.Parse(dr["EmpId"].ToString());
                userInfo.Pwd = dr["Pwd"].ToString();
                userInfo.StuName = dr["StuName"].ToString();
                userInfo.StuAge = int.Parse(dr["StuAge"].ToString());
                userInfo.Delflag = Char.Parse(dr["Delflag"].ToString());
                userInfo.ClassNo = int.Parse(dr["ClassNo"] == DBNull.Value ? "-1" : dr["ClassNo"].ToString());
                //添加到列表中
                userInfoList.Add(userInfo);
            }
            //01-06 配置数据源
            this.dataGridView1.DataSource = userInfoList;

        }
        #endregion

    }
}

Case When

　　2.5 IsNull(表达式,替换内容)函数

　　select CreateDate,IsNull(CreateDate,getDate()) from UserInfo

　　2.6 with 语句的使用　　

 select distinct(VendorName),ve.*,ba.*  from [dbo].[AS_Batch] as ba
 inner join AS_Vendor ve on ba.VendorID = ve.VendorID
 inner join AS_Equipment ae on ae.EquipmentID=ba.EquipmentID
 where 1=1 order by ve.VendorID desc

 --新建了一台设备 "联想电脑"
 select * from AS_Equipment where EquipmentID = '1AC91813-F636-43AD-82E1-0384051D0DB2';

  --新建了3个厂商
  select * from AS_Vendor where VendorID in ('065A1954-88A8-415E-BA19-549C17F3354E','EA7B0530-2D5C-4ADB-B2D7-5854C00787A7','2D8F6E94-7243-42C1-B6AD-1008F6D50CE8')

  --创建一个场景:
  --批次    厂商    数量    价格
  --批次1    A        10        100
  --批次2    B        20        200
  --批次3    C        30        300
  --批次4    A        40        400

  select * from [AS_Batch] where BatchID in ('027D504A-9EC2-43F3-BCC9-8A962831F603','FF8BA2CC-2662-469E-BB16-07DB7599FD06','187334AB-892D-4553-A928-7638067E1D77','F3768B5A-9AB2-497B-B8BB-06E81473996F')

  --根据设备ID查询供应商
 select ve.*   from [dbo].[AS_Batch] as ba
 inner join AS_Vendor ve on ba.VendorID = ve.VendorID
 inner join AS_Equipment ae on ae.EquipmentID=ba.EquipmentID
 where 1=1
 and ae.EquipmentName='联想电脑'
 order by ve.VendorID desc

--获取同一设备在不同厂商的均价(a)，计算方法：(批次1数量*批次1价格+批次2数量*批次2价格…)/(批次1数量+批次2数量…)；
 select sum(ba.EquipmentPrice*ba.EquipmentNum)/sum(ba.EquipmentNum) as EquipmentAvgPrice,sum(ba.EquipmentNum) as EquipmentAmount,ba.VendorID
 from [dbo].[AS_Batch] as ba
 inner join AS_Vendor ve on ba.VendorID = ve.VendorID
 inner join AS_Equipment ae on ae.EquipmentID=ba.EquipmentID
 where 1=1
 and ae.EquipmentName='联想电脑'
 group by ba.VendorID
 order by ba.VendorID desc

  --创建一个场景:
  --批次    厂商    数量    价格    损坏个数/次数
  --批次1    A        10        100        1/2
  --批次2    B        20        200        2/(1+2)
  --批次3    C        30        300        4/(1+1+2+1)
  --批次4    A        40        400        2/(2+3)

 --获取同一设备在不同厂商的设备正常率(p)=(总设备个数-维修设备个数)/总设备个数
 select count(distinct(af.QRCode)),ba.VendorID
 from [dbo].[AS_Batch] as ba
 inner join AS_Vendor ve on ba.VendorID = ve.VendorID
 inner join AS_Equipment ae on ae.EquipmentID=ba.EquipmentID
 inner join AS_AfterSale af on substring(af.QRCode,1,36)=ba.batchid
 where 1=1
 and ae.EquipmentName='联想电脑'
 group by ba.VendorID
 order by ba.VendorID desc

 -------------计算性厂商价比
with
pri as ( select sum(ba.EquipmentPrice*ba.EquipmentNum) as EquipmentAmountPrice, sum(ba.EquipmentPrice*ba.EquipmentNum)/sum(ba.EquipmentNum) as EquipmentAvgPrice,sum(ba.EquipmentNum) as EquipmentAmount,ba.VendorID as VendorID
 from [dbo].[AS_Batch] as ba
 inner join AS_Vendor ve on ba.VendorID = ve.VendorID
 inner join AS_Equipment ae on ae.EquipmentID=ba.EquipmentID
 where 1=1
 and ae.EquipmentName='联想电脑'
 group by ba.VendorID
),
repairs as (
 select count(distinct(af.QRCode)) as RepairsNum,ba.VendorID as VendorID
 from [dbo].[AS_Batch] as ba
 inner join AS_Vendor ve on ba.VendorID = ve.VendorID
 inner join AS_Equipment ae on ae.EquipmentID=ba.EquipmentID
 inner join AS_AfterSale af on substring(af.QRCode,1,36)=ba.batchid
 where 1=1
 and ae.EquipmentName='联想电脑'
 group by ba.VendorID
)
--设备正常率/均价
 select (EquipmentAmount-RepairsNum)/EquipmentAmountPrice from pri,repairs where pri.VendorID=repairs.VendorID;

3 DCL语言

　　--03-01分配权限
　　grant select on  UserInfo To zw

　　

4 大的备份脚本还原

5：DBA管理，

查看表字段和表字段属性

SELECT
表名=d.name,
表说明=isnull(f.value,''),
字段序号=a.colorder,
字段名=a.name,
字段标题=isnull(g.[value],''),
标识=case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')= then '√'else '' end,
主键=case when exists(SELECT  FROM sysobjects where xtype='PK' and name in (
SELECT name FROM sysindexes WHERE indid in(
SELECT indid FROM sysindexkeys WHERE id = a.id AND colid=a.colid
))) then '√' else '' end,
类型=b.name,
占用字节数=a.length,
长度=COLUMNPROPERTY(a.id,a.name,'PRECISION'),
小数位数=isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),),
允许空=case when a.isnullable= then '√'else '' end,
默认值=isnull(e.text,'')
--into ##tx
FROM syscolumns a
left join systypes b on a.xtype=b.xusertype
inner join sysobjects d on a.id=d.id and d.xtype='U' and d.name<>'dtproperties'
left join syscomments e on a.cdefault=e.id
left join sys.extended_properties g on a.id=g.class and a.colid=g.minor_id  --sql2000此处替换为：left join sysproperties g on a.id=g.id and a.colid=g.smallid
left join sys.extended_properties f on d.id=f.class and f.minor_id= --sql2000此处替换为：left join sysproperties f on d.id=f.id and f.smallid=
where d.name='ProcessPublish' --如果只查询指定表,加上此条件
order by object_name(a.id),a.colorder

查看数据表及对应的记录数

SELECT   SUM(记录条数) AS 总记录数
FROM      (SELECT   TOP () a.name AS 表名, MAX(b.rows) AS 记录条数
                 FROM      sys.sysobjects AS a INNER JOIN
                                 sys.sysindexes AS b ON a.id = b.id
                 WHERE   (a.xtype = 'u')
                 GROUP BY a.name
                 ORDER BY 记录条数 DESC) AS t1

SELECT   a.name AS 表名, MAX(b.rows) AS 记录条数
FROM      sys.sysobjects AS a INNER JOIN
                sys.sysindexes AS b ON a.id = b.id
WHERE   (a.xtype = 'u')
GROUP BY a.name
ORDER BY 记录条数 DESC