288 lines
9.8 KiB
C#
288 lines
9.8 KiB
C#
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//---------------------------------------------------------------------
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// <copyright file="SqlSelectStatement.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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//
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// @owner [....]
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// @backupOwner [....]
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//---------------------------------------------------------------------
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using System;
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using System.Collections.Generic;
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using System.Diagnostics;
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using System.Data.Common.CommandTrees;
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namespace System.Data.SqlClient.SqlGen
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{
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/// <summary>
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/// A SqlSelectStatement represents a canonical SQL SELECT statement.
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/// It has fields for the 5 main clauses
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/// <list type="number">
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/// <item>SELECT</item>
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/// <item>FROM</item>
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/// <item>WHERE</item>
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/// <item>GROUP BY</item>
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/// <item>ORDER BY</item>
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/// </list>
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/// We do not have HAVING, since the CQT does not have such a node.
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/// Each of the fields is a SqlBuilder, so we can keep appending SQL strings
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/// or other fragments to build up the clause.
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///
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/// The FromExtents contains the list of inputs in use for the select statement.
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/// There is usually just one element in this - Select statements for joins may
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/// temporarily have more than one.
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///
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/// If the select statement is created by a Join node, we maintain a list of
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/// all the extents that have been flattened in the join in AllJoinExtents
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/// <example>
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/// in J(j1= J(a,b), c)
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/// FromExtents has 2 nodes JoinSymbol(name=j1, ...) and Symbol(name=c)
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/// AllJoinExtents has 3 nodes Symbol(name=a), Symbol(name=b), Symbol(name=c)
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/// </example>
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///
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/// If any expression in the non-FROM clause refers to an extent in a higher scope,
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/// we add that extent to the OuterExtents list. This list denotes the list
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/// of extent aliases that may collide with the aliases used in this select statement.
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/// It is set by <see cref="SqlGenerator.Visit(DbVariableReferenceExpression)"/>.
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/// An extent is an outer extent if it is not one of the FromExtents.
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///
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///
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/// </summary>
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internal sealed class SqlSelectStatement : ISqlFragment
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{
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/// <summary>
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/// Whether the columns ouput by this sql statement were renamed from what given in the command tree.
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/// </summary>
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internal bool OutputColumnsRenamed
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{
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get;
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set;
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}
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/// <summary>
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/// A dictionary of output columns
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/// </summary>
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internal Dictionary<string, Symbol> OutputColumns
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{
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get;
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set;
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}
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internal List<Symbol> AllJoinExtents
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{
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get;
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// We have a setter as well, even though this is a list,
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// since we use this field only in special cases.
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set;
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}
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private List<Symbol> fromExtents;
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internal List<Symbol> FromExtents
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{
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get
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{
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if (null == fromExtents)
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{
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fromExtents = new List<Symbol>();
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}
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return fromExtents;
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}
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}
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private Dictionary<Symbol, bool> outerExtents;
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internal Dictionary<Symbol, bool> OuterExtents
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{
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get
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{
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if (null == outerExtents)
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{
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outerExtents = new Dictionary<Symbol, bool>();
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}
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return outerExtents;
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}
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}
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private readonly SqlSelectClauseBuilder select;
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internal SqlSelectClauseBuilder Select
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{
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get { return select; }
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}
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private readonly SqlBuilder from = new SqlBuilder();
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internal SqlBuilder From
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{
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get { return from; }
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}
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private SqlBuilder where;
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internal SqlBuilder Where
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{
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get
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{
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if (null == where)
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{
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where = new SqlBuilder();
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}
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return where;
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}
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}
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private SqlBuilder groupBy;
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internal SqlBuilder GroupBy
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{
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get
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{
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if (null == groupBy)
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{
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groupBy = new SqlBuilder();
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}
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return groupBy;
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}
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}
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private SqlBuilder orderBy;
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public SqlBuilder OrderBy
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{
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get
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{
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if (null == orderBy)
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{
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orderBy = new SqlBuilder();
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}
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return orderBy;
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}
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}
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//indicates whether it is the top most select statement,
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// if not Order By should be omitted unless there is a corresponding TOP
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internal bool IsTopMost
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{
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get;
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set;
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}
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#region Internal Constructor
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internal SqlSelectStatement()
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{
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this.select = new SqlSelectClauseBuilder(delegate() { return this.IsTopMost; });
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}
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#endregion
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#region ISqlFragment Members
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/// <summary>
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/// Write out a SQL select statement as a string.
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/// We have to
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/// <list type="number">
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/// <item>Check whether the aliases extents we use in this statement have
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/// to be renamed.
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/// We first create a list of all the aliases used by the outer extents.
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/// For each of the FromExtents( or AllJoinExtents if it is non-null),
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/// rename it if it collides with the previous list.
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/// </item>
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/// <item>Write each of the clauses (if it exists) as a string</item>
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/// </list>
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/// </summary>
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/// <param name="writer"></param>
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/// <param name="sqlGenerator"></param>
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public void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator)
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{
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#region Check if FROM aliases need to be renamed
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// Create a list of the aliases used by the outer extents
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// JoinSymbols have to be treated specially.
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List<string> outerExtentAliases = null;
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if ((null != outerExtents) && (0 < outerExtents.Count))
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{
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foreach (Symbol outerExtent in outerExtents.Keys)
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{
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JoinSymbol joinSymbol = outerExtent as JoinSymbol;
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if (joinSymbol != null)
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{
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foreach (Symbol symbol in joinSymbol.FlattenedExtentList)
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{
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if (null == outerExtentAliases) { outerExtentAliases = new List<string>(); }
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outerExtentAliases.Add(symbol.NewName);
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}
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}
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else
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{
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if (null == outerExtentAliases) { outerExtentAliases = new List<string>(); }
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outerExtentAliases.Add(outerExtent.NewName);
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}
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}
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}
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// An then rename each of the FromExtents we have
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// If AllJoinExtents is non-null - it has precedence.
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// The new name is derived from the old name - we append an increasing int.
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List<Symbol> extentList = this.AllJoinExtents ?? this.fromExtents;
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if (null != extentList)
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{
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foreach (Symbol fromAlias in extentList)
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{
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if ((null != outerExtentAliases) && outerExtentAliases.Contains(fromAlias.Name))
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{
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int i = sqlGenerator.AllExtentNames[fromAlias.Name];
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string newName;
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do
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{
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++i;
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newName = fromAlias.Name + i.ToString(System.Globalization.CultureInfo.InvariantCulture);
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}
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while (sqlGenerator.AllExtentNames.ContainsKey(newName));
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sqlGenerator.AllExtentNames[fromAlias.Name] = i;
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fromAlias.NewName = newName;
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// Add extent to list of known names (although i is always incrementing, "prefix11" can
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// eventually collide with "prefix1" when it is extended)
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sqlGenerator.AllExtentNames[newName] = 0;
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}
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// Add the current alias to the list, so that the extents
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// that follow do not collide with me.
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if (null == outerExtentAliases) { outerExtentAliases = new List<string>(); }
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outerExtentAliases.Add(fromAlias.NewName);
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}
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}
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#endregion
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// Increase the indent, so that the Sql statement is nested by one tab.
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writer.Indent += 1; // ++ can be confusing in this context
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this.select.WriteSql(writer, sqlGenerator);
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writer.WriteLine();
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writer.Write("FROM ");
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this.From.WriteSql(writer, sqlGenerator);
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if ((null != this.where) && !this.Where.IsEmpty)
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{
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writer.WriteLine();
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writer.Write("WHERE ");
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this.Where.WriteSql(writer, sqlGenerator);
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}
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if ((null != this.groupBy) && !this.GroupBy.IsEmpty)
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{
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writer.WriteLine();
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writer.Write("GROUP BY ");
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this.GroupBy.WriteSql(writer, sqlGenerator);
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}
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if ((null != this.orderBy) && !this.OrderBy.IsEmpty && (this.IsTopMost || this.Select.Top != null))
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{
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writer.WriteLine();
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writer.Write("ORDER BY ");
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this.OrderBy.WriteSql(writer, sqlGenerator);
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}
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--writer.Indent;
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}
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#endregion
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}
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}
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