基类
/// <summary>
/// 执行SQL查询,返回分页记录集
/// </summary>
/// <param name= "sql "> SQL语句 </param>
/// <param name= "startRowIndex "> 开始行,1开始 </param>
/// <param name= "maximumRows "> 最大返回行数 </param>
/// <param name= "keyColumn "> 主键列。用于not in分页 </param>
/// <returns> </returns>
public virtual DataSet Query(String sql, Int32 startRowIndex, Int32 maximumRows, String keyColumn)
{
// 从第一行开始,不需要分页
if (startRowIndex <= 1)
{
if (maximumRows < 1)
return Query(sql);
else
return Query(String.Format( "Select Top {0} * From ({1}) a ", maximumRows, sql));
}
if (maximumRows < 1)
sql = String.Format( "Select * From ({1}) b Where {2} Not In(Select Top {0} {2} From ({1}) a) ", startRowIndex - 1, sql, keyColumn);
else
sql = String.Format( "Select Top {0} * From ({1}) b Where {2} Not In(Select Top {3} {2} From ({1}) a) ", startRowIndex + maximumRows - 1, sql, keyColumn, startRowIndex - 1);
return Query(sql);
}
派生类
public override DataSet Query(string sql, int startRowIndex, int maximumRows, string keyColumn)
{
// 如果没有Order By,直接调用基类方法
// 先用字符串判断,如果命中率高,这样可以提高处理效率
if (!sql.Contains( "order ")) return base.Query(sql, startRowIndex, maximumRows, keyColumn);
if (!sql.ToLower().Contains( "order ")) return base.Query(sql, startRowIndex, maximumRows, keyColumn);
// 使用正则进行严格判断。必须包含Order By,并且它右边没有右括号),表明有order by,且不是子查询的,才需要特殊处理
MatchCollection ms = Regex.Matches(sql, @ "\border\s*by\b[^)]+$ ", RegexOptions.Compiled | RegexOptions.IgnoreCase);
if (ms == null || ms.Count < 1 || ms[0].Index < 1)
{
return base.Query(sql, startRowIndex, maximumRows, keyColumn);
}
// 已确定该sql最外层含有order by,再检查最外层是否有top。因为没有top的order by是不允许作为子查询的
if (!Regex.IsMatch(sql, @ "^[^(]+\btop\b ", RegexOptions.Compiled | RegexOptions.IgnoreCase))
{
return base.Query(sql, startRowIndex, maximumRows, keyColumn);
}
String orderBy = sql.Substring(ms[0].Index);
sql = sql.Substring(0, ms[0].Index);
// 从第一行开始,不需要分页
if (startRowIndex <= 1)
{
if (maximumRows < 1)
return Query(sql);
else
return Query(String.Format( "Select Top {0} * From ({1}) a {2} ", maximumRows, sql, orderBy));