发布于 2016-06-05 00:06:33 | 203 次阅读 | 评论: 0 | 来源: 网友投递
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。
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));
}
}
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");
}