Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / SqlClient / SqlGen / SqlSelectStatement.cs / 1305376 / SqlSelectStatement.cs
//---------------------------------------------------------------------- //// Copyright (c) Microsoft Corporation. All rights reserved. // // // @owner [....] // @backupOwner [....] //--------------------------------------------------------------------- using System; using System.Collections.Generic; using System.Diagnostics; using System.Data.Common.CommandTrees; namespace System.Data.SqlClient.SqlGen { ////// A SqlSelectStatement represents a canonical SQL SELECT statement. /// It has fields for the 5 main clauses /// internal sealed class SqlSelectStatement : ISqlFragment { //////
/// We do not have HAVING, since the CQT does not have such a node. /// Each of the fields is a SqlBuilder, so we can keep appending SQL strings /// or other fragments to build up the clause. /// /// The FromExtents contains the list of inputs in use for the select statement. /// There is usually just one element in this - Select statements for joins may /// temporarily have more than one. /// /// If the select statement is created by a Join node, we maintain a list of /// all the extents that have been flattened in the join in AllJoinExtents ///- SELECT
///- FROM
///- WHERE
///- GROUP BY
///- ORDER BY
////// in J(j1= J(a,b), c) /// FromExtents has 2 nodes JoinSymbol(name=j1, ...) and Symbol(name=c) /// AllJoinExtents has 3 nodes Symbol(name=a), Symbol(name=b), Symbol(name=c) /// /// /// If any expression in the non-FROM clause refers to an extent in a higher scope, /// we add that extent to the OuterExtents list. This list denotes the list /// of extent aliases that may collide with the aliases used in this select statement. /// It is set by. /// An extent is an outer extent if it is not one of the FromExtents. /// /// /// /// Whether the columns ouput by this sql statement were renamed from what given in the command tree. /// internal bool OutputColumnsRenamed { get; set; } ////// A dictionary of output columns /// internal DictionaryOutputColumns { get; set; } internal List AllJoinExtents { get; // We have a setter as well, even though this is a list, // since we use this field only in special cases. set; } private List fromExtents; internal List FromExtents { get { if (null == fromExtents) { fromExtents = new List (); } return fromExtents; } } private Dictionary outerExtents; internal Dictionary OuterExtents { get { if (null == outerExtents) { outerExtents = new Dictionary (); } return outerExtents; } } private readonly SqlSelectClauseBuilder select; internal SqlSelectClauseBuilder Select { get { return select; } } private readonly SqlBuilder from = new SqlBuilder(); internal SqlBuilder From { get { return from; } } private SqlBuilder where; internal SqlBuilder Where { get { if (null == where) { where = new SqlBuilder(); } return where; } } private SqlBuilder groupBy; internal SqlBuilder GroupBy { get { if (null == groupBy) { groupBy = new SqlBuilder(); } return groupBy; } } private SqlBuilder orderBy; public SqlBuilder OrderBy { get { if (null == orderBy) { orderBy = new SqlBuilder(); } return orderBy; } } //indicates whether it is the top most select statement, // if not Order By should be omitted unless there is a corresponding TOP internal bool IsTopMost { get; set; } #region Internal Constructor internal SqlSelectStatement() { this.select = new SqlSelectClauseBuilder(delegate() { return this.IsTopMost; }); } #endregion #region ISqlFragment Members /// /// Write out a SQL select statement as a string. /// We have to /// /// /// public void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator) { #region Check if FROM aliases need to be renamed // Create a list of the aliases used by the outer extents // JoinSymbols have to be treated specially. List///
///- Check whether the aliases extents we use in this statement have /// to be renamed. /// We first create a list of all the aliases used by the outer extents. /// For each of the FromExtents( or AllJoinExtents if it is non-null), /// rename it if it collides with the previous list. ///
///- Write each of the clauses (if it exists) as a string
///outerExtentAliases = null; if ((null != outerExtents) && (0 < outerExtents.Count)) { foreach (Symbol outerExtent in outerExtents.Keys) { JoinSymbol joinSymbol = outerExtent as JoinSymbol; if (joinSymbol != null) { foreach (Symbol symbol in joinSymbol.FlattenedExtentList) { if (null == outerExtentAliases) { outerExtentAliases = new List (); } outerExtentAliases.Add(symbol.NewName); } } else { if (null == outerExtentAliases) { outerExtentAliases = new List (); } outerExtentAliases.Add(outerExtent.NewName); } } } // An then rename each of the FromExtents we have // If AllJoinExtents is non-null - it has precedence. // The new name is derived from the old name - we append an increasing int. List extentList = this.AllJoinExtents ?? this.fromExtents; if (null != extentList) { foreach (Symbol fromAlias in extentList) { if ((null != outerExtentAliases) && outerExtentAliases.Contains(fromAlias.Name)) { int i = sqlGenerator.AllExtentNames[fromAlias.Name]; string newName; do { ++i; newName = fromAlias.Name + i.ToString(System.Globalization.CultureInfo.InvariantCulture); } while (sqlGenerator.AllExtentNames.ContainsKey(newName)); sqlGenerator.AllExtentNames[fromAlias.Name] = i; fromAlias.NewName = newName; // Add extent to list of known names (although i is always incrementing, "prefix11" can // eventually collide with "prefix1" when it is extended) sqlGenerator.AllExtentNames[newName] = 0; } // Add the current alias to the list, so that the extents // that follow do not collide with me. if (null == outerExtentAliases) { outerExtentAliases = new List (); } outerExtentAliases.Add(fromAlias.NewName); } } #endregion // Increase the indent, so that the Sql statement is nested by one tab. writer.Indent += 1; // ++ can be confusing in this context this.select.WriteSql(writer, sqlGenerator); writer.WriteLine(); writer.Write("FROM "); this.From.WriteSql(writer, sqlGenerator); if ((null != this.where) && !this.Where.IsEmpty) { writer.WriteLine(); writer.Write("WHERE "); this.Where.WriteSql(writer, sqlGenerator); } if ((null != this.groupBy) && !this.GroupBy.IsEmpty) { writer.WriteLine(); writer.Write("GROUP BY "); this.GroupBy.WriteSql(writer, sqlGenerator); } if ((null != this.orderBy) && !this.OrderBy.IsEmpty && (this.IsTopMost || this.Select.Top != null)) { writer.WriteLine(); writer.Write("ORDER BY "); this.OrderBy.WriteSql(writer, sqlGenerator); } --writer.Indent; } #endregion } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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