发布于 2016-06-05 00:06:33 | 203 次阅读 | 评论: 0 | 来源: 网友投递

这里有新鲜出炉的SQL教程，程序狗速度看过来！

SQL 结构化查询语言

结构化查询语言(Structured Query Language)简称SQL(发音：/ˈɛs kjuː ˈɛl/ "S-Q-L")，结构化查询语言是一种数据库查询和程序设计语言，用于存取数据以及查询、更新和管理关系数据库系统；同时也是数据库脚本文件的扩展名。结构化查询语言是高级的非过程化编程语言，允许用户在高层数据结构上 工作。它不要求用户指定对数据的存放方法，也不需要用户了解具体的数据存放方式，所以具有完全不同底层结构的不同数据库系统, 可以使用相同的结构化查询语言作为数据输入与管理的接口。结构化查询语言语句可以嵌套，这使它具有极大的灵活性和强大的功能。

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前些时间看了玉开兄的“如此高效通用的分页存储过程是带有sql注入漏洞的”这篇文章，才突然想起某个项目也是使用了累似的通用分页存储过程。
使用这种通用的存储过程进行分页查询，想要防SQL注入，只能对输入的参数进行过滤，例如将一个单引号“'”转换成两个单引号“''”，但这种做法是不安全的，厉害的黑客可以通过编码的方式绕过单引号的过滤，要想有效防SQL注入，只有参数化查询才是最终的解决方案。但问题就出在这种通用分页存储过程是在存储过程内部进行SQL语句拼接，根本无法修改为参数化的查询语句，因此这种通用分页存储过程是不可取的。但是如果不用通用的分页存储过程，则意味着必须为每个具体的分页查询写一个分页存储过程，这会增加不少的工作量。
经过几天的时间考虑之后，想到了一个用代码来生成参数化的通用分页查询语句的解决方案。代码如下：

 
public class PagerQuery 
{ 
private int _pageIndex; 
private int _pageSize = 20; 
private string _pk; 
private string _fromClause; 
private string _groupClause; 
private string _selectClause; 
private string _sortClause; 
private StringBuilder _whereClause; 
public DateTime DateFilter = DateTime.MinValue; 
protected QueryBase() 
{ 
_whereClause = new StringBuilder(); 
} 
/**//// <summary> 
/// 主键 
/// </summary> 
public string PK 
{ 
get { return _pk; } 
set { _pk = value; } 
} 
public string SelectClause 
{ 
get { return _selectClause; } 
set { _selectClause = value; } 
} 
public string FromClause 
{ 
get { return _fromClause; } 
set { _fromClause = value; } 
} 
public StringBuilder WhereClause 
{ 
get { return _whereClause; } 
set { _whereClause = value; } 
} 
public string GroupClause 
{ 
get { return _groupClause; } 
set { _groupClause = value; } 
} 
public string SortClause 
{ 
get { return _sortClause; } 
set { _sortClause = value; } 
} 
/**//// <summary> 
/// 当前页数 
/// </summary> 
public int PageIndex 
{ 
get { return _pageIndex; } 
set { _pageIndex = value; } 
} 
/**//// <summary> 
/// 分页大小 
/// </summary> 
public int PageSize 
{ 
get { return _pageSize; } 
set { _pageSize = value; } 
} 
/**//// <summary> 
/// 生成缓存Key 
/// </summary> 
/// <returns></returns> 
public override string GetCacheKey() 
{ 
const string keyFormat = "Pager-SC:{0}-FC:{1}-WC:{2}-GC:{3}-SC:{4}"; 
return string.Format(keyFormat, SelectClause, FromClause, WhereClause, GroupClause, SortClause); 
} 
/**//// <summary> 
/// 生成查询记录总数的SQL语句 
/// </summary> 
/// <returns></returns> 
public string GenerateCountSql() 
{ 
StringBuilder sb = new StringBuilder(); 
sb.AppendFormat(" from {0}", FromClause); 
if (WhereClause.Length > 0) 
sb.AppendFormat(" where 1=1 {0}", WhereClause); 
if (!string.IsNullOrEmpty(GroupClause)) 
sb.AppendFormat(" group by {0}", GroupClause); 
return string.Format("Select count(0) {0}", sb); 
} 
/**//// <summary> 
/// 生成分页查询语句，包含记录总数 
/// </summary> 
/// <returns></returns> 
public string GenerateSqlIncludeTotalRecords() 
{ 
StringBuilder sb = new StringBuilder(); 
if (string.IsNullOrEmpty(SelectClause)) 
SelectClause = "*"; 
if (string.IsNullOrEmpty(SortClause)) 
SortClause = PK; 
int start_row_num = (PageIndex - 1)*PageSize + 1; 
sb.AppendFormat(" from {0}", FromClause); 
if (WhereClause.Length > 0) 
sb.AppendFormat(" where 1=1 {0}", WhereClause); 
if (!string.IsNullOrEmpty(GroupClause)) 
sb.AppendFormat(" group by {0}", GroupClause); 
string countSql = string.Format("Select count(0) {0};", sb); 
string tempSql = 
string.Format( 
"WITH t AS (SELECT ROW_NUMBER() OVER(ORDER BY {0}) as row_number,{1}{2}) Select * from t where row_number BETWEEN {3} and {4};", 
SortClause, SelectClause, sb, start_row_num, (start_row_num + PageSize - 1)); 
return tempSql + countSql; 
} 
/**//// <summary> 
/// 生成分页查询语句 
/// </summary> 
/// <returns></returns> 
public override string GenerateSql() 
{ 
StringBuilder sb = new StringBuilder(); 
if (string.IsNullOrEmpty(SelectClause)) 
SelectClause = "*"; 
if (string.IsNullOrEmpty(SortClause)) 
SortClause = PK; 
int start_row_num = (PageIndex - 1)*PageSize + 1; 
sb.AppendFormat(" from {0}", FromClause); 
if (WhereClause.Length > 0) 
sb.AppendFormat(" where 1=1 {0}", WhereClause); 
if (!string.IsNullOrEmpty(GroupClause)) 
sb.AppendFormat(" group by {0}", GroupClause); 
return 
string.Format( 
"WITH t AS (SELECT ROW_NUMBER() OVER(ORDER BY {0}) as row_number,{1}{2}) Select * from t where row_number BETWEEN {3} and {4}", 
SortClause, SelectClause, sb, start_row_num, (start_row_num + PageSize - 1)); 
} 
} 

使用方法：

 
PagerQuery query = new PagerQuery(); 
query.PageIndex = 1; 
query.PageSize = 20; 
query.PK = "ID"; 
query.SelectClause = "*"; 
query.FromClause = "TestTable"; 
query.SortClause = "ID DESC"; 
if (!string.IsNullOrEmpty(code)) 
{ 
query.WhereClause.Append(" and ID= @ID"); 
} 

a) GenerateCountSql ()方法生成的语句为：
Select count(0) from TestTable Where 1=1 and ID= @ID
b) GenerateSql()方法生成的语句为：
WITH t AS (SELECT ROW_NUMBER() OVER(ORDER BY ECID DESC) as row_number, * from TestTable where 1=1 and ID= @ID) Select * from t where row_number BETWEEN 1 and 20
c) GenerateSqlIncludetTotalRecords()方法生成的语句为：
WITH t AS (SELECT ROW_NUMBER() OVER(ORDER BY E.ECID DESC) as row_number,* from TestTable where 1=1 and ID= @ID) Select * from t where row_number BETWEEN 1 and 20;Select count(0) from ECBasicInfo where 1=1 and ID= @ID;

注意：以上代码生成的SQL语句是曾对SQL SERVER 2005以上版本的，希望这些代码对大家有用