sql查询语句如何解析成分页查询？

我们公司主要mysql存储数据，因此也封装了比较好用mysql通用方法，然后，我们做大量接口，在处理分页查询接口，没有很好分查询方法。sql查询 语句如何解析成“分页查询”和“总统计”两条语句。可能，很多人在处理“总统计”是这样:“select count(*) from (<sql原查询语句>) ”，而不是把原sql查询语句中columns替换成“count(*)”；相比前者统计查询效率高不高，大家心知肚明。“分页查询”很简单，对于mysql语句就是在原sql查询语句后面加上“limit 数字 offset 数字”

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace MySqlTest
{
class Program
{
static void Main(string[] args)
{
string sql = "select id,code,name,modifytime,storeid from retail_cashier where profileid=@profileid and  storeId=@storeId order by id";
var parts = MysqlPageHelper.BuildPageQuery(sql, 1, 20);

Console.WriteLine("sql：{0}；",parts.Sql);
Console.WriteLine("SqlCount：{0}", parts.SqlCount);
Console.WriteLine("SqlPage：{0}",parts.SqlPage);
Console.WriteLine("SqlOrderBy：{0}", parts.SqlOrderBy);
Console.ReadKey();
}
}

public class MysqlPageHelper
{
public Regex RegexColumns = new Regex(@"\A\s*SELECT\s+((?:\((?>\((?<depth>)|\)(?<-depth>)|.?)*(?(depth)(?!))\)|.)*?)(?<!,\s+)\bFROM\b",
RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.Singleline | RegexOptions.Compiled);

public Regex RegexDistinct = new Regex(@"\ADISTINCT\s",
RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.Singleline | RegexOptions.Compiled);

public Regex RegexOrderBy =
new Regex(
@"\bORDER\s+BY\s+(?!.*?(?:\)|\s+)AS\s)(?:\((?>\((?<depth>)|\)(?<-depth>)|.?)*(?(depth)(?!))\)|[\[\]`""\w\(\)\.])+(?:\s+(?:ASC|DESC))?(?:\s*,\s*(?:\((?>\((?<depth>)|\)(?<-depth>)|.?)*(?(depth)(?!))\)|[\[\]`""\w\(\)\.])+(?:\s+(?:ASC|DESC))?)*",
RegexOptions.RightToLeft | RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.Singleline | RegexOptions.Compiled);

private string _sqlSelectRemoved = null;
public void SplitSql(string sql, long skip, long take)
{
this.Sql = sql;
this.SqlCount = null;
this.SqlOrderBy = null;

// 从中提取列
var m = RegexColumns.Match(this.Sql);
if (!m.Success)
throw new Exception("无法解析分页查询的SQL语句");

// sql语句中columns替换成count(*)
var g = m.Groups[1];
this._sqlSelectRemoved = this.Sql.Substring(g.Index);

if (RegexDistinct.IsMatch(this._sqlSelectRemoved))
this.SqlCount = this.Sql.Substring(0, g.Index) + "COUNT(" + m.Groups[1].ToString().Trim() + ") " + sql.Substring(g.Index + g.Length);
else
this.SqlCount = this.Sql.Substring(0, g.Index) + "COUNT(*) " + sql.Substring(g.Index + g.Length);

// sql语句最后order by
m = RegexOrderBy.Match(this.SqlCount);
if (m.Success)
{
g = m.Groups[0];
this.SqlOrderBy = g.ToString();
this.SqlCount = this.SqlCount.Substring(0, g.Index) + this.SqlCount.Substring(g.Index + g.Length);
}
//分页读取数据
SqlPage = string.Format("{0}\nLIMIT {1} OFFSET {2}", this.Sql, take, skip);
}

public static MysqlPageHelper BuildPageQuery(string sql, long skip, long take)
{
var page=new MysqlPageHelper();
page.SplitSql(sql,skip,take);
return page;
}

public string Sql { get; private set; }
public string SqlPage { get;private set; }
public string SqlCount { get;private set; }
public string SqlOrderBy { get;private set; }
}
}