317 lines
14 KiB
C#
317 lines
14 KiB
C#
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using System.Text;
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using System;
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using System.Text.RegularExpressions;
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namespace CYQ.Data.SQL
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{
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/// <summary>
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/// Sql分页语句类
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/// </summary>
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internal partial class SqlCreateForPager
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{
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public static string GetSql(DalType dalType, string version, int pageIndex, int pageSize, object objWhere, string tableName, int rowCount, string columns, string primaryKey, bool primaryKeyIsIdentity)
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{
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if (string.IsNullOrEmpty(columns))
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{
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columns = "*";
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}
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pageIndex = pageIndex == 0 ? 1 : pageIndex;
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string where = SqlFormat.GetIFieldSql(objWhere);
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if (string.IsNullOrEmpty(where))
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{
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where = "1=1";
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}
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if (pageSize == 0)
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{
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return string.Format(top1Pager, columns, tableName, where);
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}
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if (rowCount > 0)//分页查询。
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{
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where = SqlCreate.AddOrderBy(where, primaryKey);
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}
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int topN = pageIndex * pageSize;//Top N 最大数
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int max = (pageIndex - 1) * pageSize;
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int rowStart = (pageIndex - 1) * pageSize + 1;
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int rowEnd = rowStart + pageSize - 1;
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string orderBy = string.Empty;
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if (pageIndex == 1 && dalType != DalType.Oracle)//第一页（oracle时 rownum 在排序条件为非数字时，和row_number()的不一样，会导致结果差异，所以分页统一用row_number()。）
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{
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switch (dalType)
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{
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case DalType.Access:
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case DalType.MsSql:
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case DalType.Sybase:
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return string.Format(top1Pager, "top " + pageSize + " " + columns, tableName, where);
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//case DalType.Oracle:
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// return string.Format(top1Pager, columns, tableName, "rownum<=" + pageSize + " and " + where);
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case DalType.SQLite:
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case DalType.MySql:
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case DalType.PostgreSQL:
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return string.Format(top1Pager, columns, tableName, where + " limit " + pageSize);
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}
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}
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else
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{
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switch (dalType)
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{
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case DalType.Access:
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case DalType.MsSql:
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case DalType.Sybase:
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int leftNum = rowCount % pageSize;
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int pageCount = leftNum == 0 ? rowCount / pageSize : rowCount / pageSize + 1;//页数
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if (pageIndex == pageCount && dalType != DalType.Sybase) // 最后一页Sybase 不支持双Top order by
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{
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return string.Format(top2Pager, pageSize+" "+columns, "top " + (leftNum == 0 ? pageSize : leftNum) + " * ", tableName, ReverseOrderBy(where, primaryKey), GetOrderBy(where, false, primaryKey));//反序
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}
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if ((pageCount > 1000 || rowCount > 100000) && pageIndex > pageCount / 2) // 页数过后半段，反转查询
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{
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orderBy = GetOrderBy(where, false, primaryKey);
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where = ReverseOrderBy(where, primaryKey);//事先反转一次。
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topN = rowCount - max;//取后面的
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int rowStartTemp = rowCount - rowEnd;
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rowEnd = rowCount - rowStart;
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rowStart = rowStartTemp;
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}
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break;
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}
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}
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switch (dalType)
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{
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case DalType.MsSql:
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case DalType.Oracle:
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if (version.StartsWith("08"))
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{
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goto temtable;
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// goto top3;//sql 2000
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}
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int index = tableName.LastIndexOf(')');
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if (index > 0)
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{
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tableName = tableName.Substring(0, index + 1);
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}
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string v = dalType == DalType.Oracle ? "" : " v";
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string onlyWhere = "where " + SqlCreate.RemoveOrderBy(where);
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onlyWhere = SqlFormat.RemoveWhereOneEqualsOne(onlyWhere);
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return string.Format(rowNumberPager, GetOrderBy(where, false, primaryKey), (columns == "*" ? "t.*" : columns), tableName, onlyWhere, v, rowStart, rowEnd);
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case DalType.Sybase:
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temtable:
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if (primaryKeyIsIdentity)
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{
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bool isOk = columns == "*";
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if (!isOk)
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{
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string kv = SqlFormat.NotKeyword(primaryKey);
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string[] items = columns.Split(',');
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foreach (string item in items)
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{
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if (string.Compare(SqlFormat.NotKeyword(item), kv, StringComparison.OrdinalIgnoreCase) == 0)
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{
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isOk = true;
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break;
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}
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}
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}
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else
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{
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columns = "t.*";
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index = tableName.LastIndexOf(')');
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if (index > 0)
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{
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tableName = tableName.Substring(0, index + 1);
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}
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tableName += " t ";
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}
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if (isOk)
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{
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return string.Format(tempTablePagerWithIdentity, DateTime.Now.Millisecond, topN, primaryKey, tableName, where, pageSize, columns, rowStart, rowEnd, orderBy);
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}
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}
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return string.Format(tempTablePager, DateTime.Now.Millisecond, pageIndex * pageSize + " " + columns, tableName, where, pageSize, rowStart, rowEnd, orderBy);
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case DalType.Access:
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top3:
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if (!string.IsNullOrEmpty(orderBy)) // 反转查询
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{
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return string.Format(top4Pager,columns, (rowCount - max > pageSize ? pageSize : rowCount - max), topN, tableName, where, GetOrderBy(where, true, primaryKey), GetOrderBy(where, false, primaryKey), orderBy);
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}
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return string.Format(top3Pager, (rowCount - max > pageSize ? pageSize : rowCount - max),columns, topN, tableName, where, GetOrderBy(where, true, primaryKey), GetOrderBy(where, false, primaryKey));
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case DalType.SQLite:
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case DalType.MySql:
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case DalType.PostgreSQL:
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if (max > 500000 && primaryKeyIsIdentity && Convert.ToString(objWhere) == "" && !tableName.Contains(" "))//单表大数量时的优化成主键访问。
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{
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where = string.Format("{0}>=(select {0} from {1} limit {2}, 1) limit {3}", primaryKey, tableName, max, pageSize);
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return string.Format(top1Pager, columns, tableName, where);
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}
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return string.Format(top1Pager, columns, tableName, where + " limit " + pageSize + " offset " + max);
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}
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return (string)Error.Throw("Pager::No Be Support:" + dalType.ToString());
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}
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/// <summary>
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/// 首页查询
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/// </summary>
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private const string top1Pager = "select {0} from {1} where {2}";
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/// <summary>
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/// 最后一页查询
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/// </summary>
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private const string top2Pager = "select top {0} from (select {1} from {2} where {3}) v {4}";
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/// <summary>
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/// 前半段分页查询
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/// </summary>
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private const string top3Pager = @"select top {0} {1} from (select top {0} * from (select top {2} * from {3} where {4}) v {5}) v {6}";
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/// <summary>
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/// 后半段分页查询（即倒过来查询）
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/// </summary>
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private const string top4Pager = @"select {0} from (select top {1} * from (select top {1} * from (select top {2} * from {3} where {4}) v {5}) v {6}) v {7}";
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/// <summary>
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/// MSSQL、Oracle的行号分页
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/// </summary>
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private const string rowNumberPager = "select * from(select row_number() over ({0}) cyqrownum,{1} from {2} t {3}){4} where cyqrownum between {5} and {6}";
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/// <summary>
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/// 临时表分页（不带自增加序列）
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/// </summary>
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private const string tempTablePager = @"select top {1},cyqrownum=identity(int) into #tmp{0} from {2} where {3} select top {4} * from #tmp{0} where cyqrownum between {5} and {6} {7} drop table #tmp{0}";
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/// <summary>
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/// 临时表分页（带自增加序列）
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/// </summary>
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private const string tempTablePagerWithIdentity = @"select top {1} cast({2} as int) cyqrowid,cyqrownum=identity(int) into #tmp{0} from {3} where {4} select top {5} {6} from #tmp{0} left join {3} on {2}=cyqrowid where cyqrownum between {7} and {8} {9} drop table #tmp{0}";
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///// <summary>
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///// 格式化where，需要有order by
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///// </summary>
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//private static string GetWhereFixOrderBy(string where)
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//{
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// if (where.IndexOf("order by", StringComparison.OrdinalIgnoreCase) == -1)
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// {
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// where += " order by " + defaultOrderByKey;
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// }
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// return where;
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//}
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/// <summary>
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/// 获取order by 语句
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/// </summary>
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/// <param name="reverse">排序是否反转</param>
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internal static string GetOrderBy(string where, bool reverse, string primaryKey)
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{
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string orderby = " order by " + primaryKey + " ";
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int index = where.IndexOf("order by ", StringComparison.OrdinalIgnoreCase);//order by XXasc , Xdesc desc
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if (index > -1)
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{
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if (where.IndexOf("asc", StringComparison.OrdinalIgnoreCase) > -1 || where.IndexOf("desc", StringComparison.OrdinalIgnoreCase) > -1)
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{
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where = where.Substring(index);//不需要反转，直接取排序内容返回。
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if (!reverse)
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{
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return where;
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}
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where = where.Replace(",", " , ");
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string[] items = where.Split(' ');
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orderby = string.Empty;
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foreach (string item in items)
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{
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switch (item.ToLower())
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{
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case "asc":
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orderby += "desc ";
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break;
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case "desc":
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orderby += "asc ";
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break;
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default:
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orderby += item + " ";
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break;
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}
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}
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return orderby.Trim();
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}
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else if (reverse)
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{
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orderby = where + " desc";
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}
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}
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else
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{
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orderby += reverse ? "desc" : "asc";
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}
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return orderby.ToLower();
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}
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private static string ReverseOrderBy(string where, string primaryKey)
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{
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int index = where.IndexOf("order by ", StringComparison.OrdinalIgnoreCase);
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if (index > -1)
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{
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string orderby = string.Empty;
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string onlyOrderBy = where.Substring(index).Trim();//order by t_sort,t_course_code desc,t_id "
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where = where.Substring(0, index);
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onlyOrderBy = onlyOrderBy.Replace(",", " , ");
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string[] items = onlyOrderBy.Split(' ');
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orderby = string.Empty;
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bool isAscOrDesc = false;
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foreach (string item in items)
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{
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switch (item.ToLower())
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{
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case "asc":
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orderby += "desc ";
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isAscOrDesc = true;
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break;
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case "desc":
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orderby += "asc ";
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isAscOrDesc = true;
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break;
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case ","://遇上分号，如果前面没有升降序，默认为升，转为降。
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if (!isAscOrDesc)
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{
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orderby += "desc";
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}
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orderby += item;
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isAscOrDesc = false;
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break;
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case "":
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break;
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default:
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orderby += item + " ";
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isAscOrDesc = false;
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break;
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}
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}
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string lastItem = items[items.Length - 1].ToLower();
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if (lastItem != "asc" && lastItem != "desc") // 最后一项为空时，补desc
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{
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orderby += "desc";
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}
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return where + orderby.Trim();
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}
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else
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{
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return where + " order by " + primaryKey + " desc";
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}
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}
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///// <summary>
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///// 是否降序
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///// </summary>
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//private static bool IsOrderByDesc(string where)
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//{
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// int index = where.IndexOf("order by", StringComparison.OrdinalIgnoreCase);
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// if (index > -1 && where.IndexOf("desc", StringComparison.OrdinalIgnoreCase) > -1)
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// {
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// return true;
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// }
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// return false;
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//}
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//internal static string defaultOrderByKey = "id";
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}
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}
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