File indexing completed on 2022-11-29 19:02:26

0001 /* This file is part of the KDE project
0002    Copyright (C) 2003-2017 Jarosław Staniek <staniek@kde.org>
0003 
0004    This library is free software; you can redistribute it and/or
0005    modify it under the terms of the GNU Library General Public
0006    License as published by the Free Software Foundation; either
0007    version 2 of the License, or (at your option) any later version.
0008 
0009    This library is distributed in the hope that it will be useful,
0010    but WITHOUT ANY WARRANTY; without even the implied warranty of
0011    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
0012    Library General Public License for more details.
0013 
0014    You should have received a copy of the GNU Library General Public License
0015    along with this library; see the file COPYING.LIB.  If not, write to
0016    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
0017  * Boston, MA 02110-1301, USA.
0018 */
0019 
0020 #ifndef KDB_QUERYASTERISK_H
0021 #define KDB_QUERYASTERISK_H
0022 
0023 #include "KDbField.h"
0024 
0025 class KDbQuerySchema;
0026 
0027 //! @short KDbQueryAsterisk class encapsulates information about single asterisk in query definition
0028 /*! There are two types of query asterisks:
0029 
0030  1. "Single-table" asterisk, that references all fields of given table used
0031  in the query.
0032  Example SQL statement:
0033  @code
0034  SELECT staff.*, cars.model from staff, cars WHERE staff.car = cars.number;
0035  @endcode
0036  The "staff.*" element is our "single-table" asterisk;
0037  this tells us that we want to get all fields of table "staff".
0038 
0039  2. "All-tables" asterisk, that references all fields of all tables used in the query.
0040  Example SQL statement:
0041  @code
0042  SELECT * from staff, cars WHERE staff.car = cars.number;
0043  @endcode
0044  The "*" is our "all-tables" asterisk;
0045  this tells us that we want to get all fields of all used tables (here: "staff" and "cars").
0046 
0047  There can be many asterisks of 1st type defined for given single query.
0048  There can be one asterisk of 2nd type defined for given single query.
0049 */
0050 class KDB_EXPORT KDbQueryAsterisk : public KDbField
0051 {
0052 public:
0053     /*! Constructs an "all-tables" query asterisk definition object ("*" in SQL notation).
0054 
0055      KDbQueryAsterisk objects are owned by KDbQuerySchema object
0056      (not by KDbTableSchema object like for ordinary KDbField objects)
0057      for that the KDbQueryAsterisk object was added (using KDbQuerySchema::addField()). */
0058     explicit KDbQueryAsterisk(KDbQuerySchema *query);
0059 
0060     /*! Constructs a "single-table" query asterisk definition object ("T.*" in SQL notation).
0061      @a table schema is the single table for the asterisk.
0062 
0063      KDbQueryAsterisk objects are owned by KDbQuerySchema object
0064      (not by KDbTableSchema object like for ordinary KDbField objects)
0065      for that the KDbQueryAsterisk object was added (using KDbQuerySchema::addField()). */
0066     KDbQueryAsterisk(KDbQuerySchema *query, const KDbTableSchema &table);
0067 
0068     /*! Constructs a deep copy of query asterisk definition object @a asterisk. */
0069     KDbQueryAsterisk(const KDbQueryAsterisk &asterisk);
0070 
0071     ~KDbQueryAsterisk() override;
0072 
0073     /**
0074      * @brief Returns @c true if this query asterisk is equal to @a other
0075      *
0076      * @return @c false if the objects are not equal.
0077      * Two asterisks are equal if they return the same table() and query().
0078      * This also means that both return the same value for isSingleTableAsterisk() and
0079      * isAllTableAsterisk().
0080      *
0081      * @since 3.1
0082      */
0083     bool operator==(const KDbQueryAsterisk& other) const;
0084 
0085     /**
0086      * @brief Returns @c true if this query asterisk is not equal to @a other
0087      *
0088      * @return @c false if objects are equal.
0089      *
0090      * @see operator==(const KDbQueryAsterisk&)
0091      * @since 3.1
0092      */
0093     inline bool operator!=(const KDbQueryAsterisk &other) const { return !operator==(other); }
0094 
0095     /*! @return Query object for that this asterisk object is defined */
0096     KDbQuerySchema *query();
0097 
0098     /*! @overload KDbQuerySchema *query() */
0099     const KDbQuerySchema *query() const;
0100 
0101     /*! @return table schema object for that this asterisk object is defined.
0102     If this is a "all-tables" asterisk, @c nullptr is returned. */
0103     const KDbTableSchema* table() const;
0104 
0105     /*! Sets table schema for this asterisk.
0106      If table is supplied, the asterisk become a "single-table" asterisk.
0107      If @a table is @c nullptr the asterisk becames "all-tables" asterisk. */
0108     void setTable(const KDbTableSchema *table);
0109 
0110     /*! This is convenience method that returns @c true
0111      if the asterisk has "all-tables" type (2nd type).*/
0112     bool isSingleTableAsterisk() const;
0113 
0114     /*! This is convenience method that returns @c true
0115      if the asterisk has "single-table" type (2nd type).*/
0116     bool isAllTableAsterisk() const;
0117 
0118 protected:
0119     //! @return a deep copy of this object. Used in KDbFieldList(const KDbFieldList& fl).
0120     KDbField* copy() override;
0121 
0122     KDbQueryAsterisk(KDbQuerySchema *query, const KDbTableSchema *table);
0123 
0124 private:
0125     class Private;
0126     Private * const d;
0127     KDbQueryAsterisk& operator=(const KDbQueryAsterisk &) = delete;
0128     void setTable(KDbTableSchema *table); // protect
0129 };
0130 
0131 //! Sends query asterisk information @a asterisk to debug output @a dbg.
0132 KDB_EXPORT QDebug operator<<(QDebug dbg, const KDbQueryAsterisk& asterisk);
0133 
0134 #endif