发一段非万能的sql分页代码

百度一下,发现N多万能的sql分页办法, 不过大都有一个共性,就是把一段sql的各个部分折成几个参数，然后拼接sql

而且很多都只支持单表.

我发的代码就是为了解决上面这两个问题的.

使用注意事项:

1.传入的sql必须是可以正常执行的sql

2.传入的sql必须有排序(order by )

3.如果使用的是SqlServerDialect,最好传入正确totalCount,否则最后一页的数据可能跟你想像中的不太一样,

如果是SqlServer2005Dialect的话，不存在此问题

4.基本上可以满足绝大部分的sql语句,大家可以试试复杂的sql,有兴趣的话，可以跟我联系,大家一起完善

下面这段是针对sql server 2000的,不过2005与2008一样可以用

public class SqlServerDialect:ISqlDialect
    {
        #region ISqlDialect 成员

        public string GetPageSqlText(string sql, int pageSize, int pageNum, int totalCount)
        {
            if (string.IsNullOrEmpty(sql))
                return sql;


            string orderByText = GetOrderByText(sql);
            if (string.IsNullOrEmpty(orderByText))
                throw new ArgumentException("缺少order by ");

            if (pageNum == 1)
                return GetFirstPageSqlText(sql, pageSize);

            int rowCount = pageSize;
            if (totalCount > 0)
            {
                if (totalCount < pageNum * pageSize)
                {
                    rowCount = totalCount - (pageNum - 1) * pageSize;
                }
                if (rowCount < 0)
                    rowCount = 0;
            }

            int pos = sql.IndexOf("select", StringComparison.OrdinalIgnoreCase);
            if (pos < 0)
                throw new ArgumentException("缺少select关键字", sql);

            //string orderByText = GetOrderByText(sql);
            string reverseOrderByText = GetReverseOrderByText(orderByText);
            StringBuilder sb = new StringBuilder();
            sb.AppendFormat("select * from ( select top {0} * from ( select top {1}", rowCount, pageSize * pageNum);
            sb.Append(sql.Substring(pos + "select".Length));

            sb.Append(") as temptable1 order by ");
            sb.Append(reverseOrderByText);
            sb.Append(") as temptable2 order by ");
            sb.Append(orderByText);
            return sb.ToString();

        }

        #endregion

        private static string GetFirstPageSqlText(string sql, int pageSize)
        {
            int pos = sql.IndexOf("select", StringComparison.OrdinalIgnoreCase);
            if (pos < 0)
                throw new ArgumentException("缺少select关键字", sql);

            StringBuilder sb = new StringBuilder(sql.Length + 20);
            sb.Append(sql);
            sb.Insert(pos + "select".Length + 1, String.Format("top {0} ", pageSize));
            return sb.ToString();
        }

        private static string GetOrderByText(string sql)
        {
            int len = "order by".Length;
            int pos = sql.LastIndexOf("order by", StringComparison.OrdinalIgnoreCase);
            if (pos < 0)
            {
                return string.Empty; ;
            }
            return RemoveAlias(sql.Substring(pos + len));
        }

        private static string GetReverseOrderByText(string orderByText)
        {
            StringBuilder sb = new StringBuilder();
            string[] cols = orderByText.Split(',');

            for (int i = 0; i < cols.Length; i++)
            {
                if (i > 0)
                    sb.Append(",");
                int pos = cols[i].LastIndexOf(" desc", StringComparison.OrdinalIgnoreCase);
                if (pos > -1)
                {
                    sb.Append(cols[i].Substring(0, pos)).Append(" asc");
                }
                else
                {
                    pos = cols[i].LastIndexOf(" asc", StringComparison.OrdinalIgnoreCase);
                    if (pos > -1)
                    {
                        sb.Append(cols[i].Substring(0, pos)).Append(" desc");
                    }
                    else
                    {
                        sb.Append(cols[i]).Append(" desc");
                    }
                }
            }
            return sb.ToString();

        }

        private static string RemoveAlias(string orderByText)
        {
            StringBuilder sb = new StringBuilder();

            string[] cols = orderByText.Split(',');

            for (int i = 0; i < cols.Length; i++)
            {
                if (i > 0)
                    sb.Append(",");

                int pos = cols[i].IndexOf(".");

                if (pos > -1)
                {
                    sb.Append(cols[i].Substring(pos + 1));
                }
                else
                {
                    sb.Append(cols[i]);
                }
            }
            return sb.ToString();

        }
        
    }

接着来个sqlserver2005的

 public class SqlServer2005Dialect : ISqlDialect
    {
        #region ISqlDialect 成员

        public string GetPageSqlText(string sql, int pageSize, int pageNum, int totalCount)
        {
            if (string.IsNullOrEmpty(sql))
                return sql;

            string orderByText = GetOrderByText(sql);
            if (string.IsNullOrEmpty(orderByText))
                throw new SqlNullValueException("缺少order by ");


            if (pageNum == 1)
                return GetFirstPageSqlText(sql, orderByText, pageSize);

            int startIndex = (pageNum - 1) * pageSize;
            int endIndex = startIndex + pageSize;

            int pos = sql.IndexOf("select", StringComparison.OrdinalIgnoreCase);
            if (pos < 0)
                throw new ArgumentException("缺少select关键字", sql);

            StringBuilder sb = new StringBuilder();
            sb.Append(sql);
            sb.Insert(pos + "select".Length + 1, String.Format(" top 100 percent row_number() OVER(order by {0}) AS _rowNum, ", orderByText));
            sb.AppendFormat(" ) select * from _pageSql where _rowNum between {0} and {1} ", startIndex + 1, endIndex);
            sb.Insert(0, "with _pageSql as ( ");

            return sb.ToString();
        }

        #endregion

        private static string GetFirstPageSqlText(string sql, string orderBySql, int pageSize)
        {
            int pos = sql.IndexOf("select", StringComparison.OrdinalIgnoreCase);
            if (pos < 0)
                throw new ArgumentException("缺少select关键字", sql);

            StringBuilder sb = new StringBuilder(sql.Length + 20);
            sb.Append(sql);
            sb.Insert(pos + "select".Length + 1, String.Format("top {0} ", pageSize));
            //sb.Append(" " + orderBySql);
            return sb.ToString();
        }

        private static string GetOrderByText(string sql)
        {
            int len = "order by".Length;
            int pos = sql.LastIndexOf("order by", StringComparison.OrdinalIgnoreCase);
            if (pos < 0)
            {
                return string.Empty; ;
            }
            return sql.Substring(pos + len);
        }
        
    }

像oracle/sqlite/mysql的，就很简单，不发了.

顺便把接口也发一下

    public interface ISqlDialect
    {
        string GetPageSqlText(string sql, int pageSize, int pageNum, int totalCount);

    }