SQLite

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains C code routines that are called by the parser
** to handle SELECT statements in SQLite.
**
** $Id: select.c,v 1.377 2008/01/02 17:11:14 danielk1977 Exp $
*/
#include "sqliteInt.h"


/*
** Delete all the content of a Select structure but do not deallocate
** the select structure itself.

  iMem = pParse->nMem;
  pParse->nMem += n+1;
  sqlite3VdbeAddOp(v, OP_MemInt, n, iMem);
  if( nColumn>0 ){
    for(i=0; i<nColumn; i++){
      sqlite3VdbeOp3Int(v, OP_Column, srcTab, i, iMem+i+1);
    }
  }else if( eDest!=SRT_Exists ){
    /* If the destination is an EXISTS(...) expression, the actual
    ** values returned by the SELECT are not required.
    */
    for(i=0; i<n; i++){
      sqlite3ExprIntoReg(pParse, pEList->a[i].pExpr, iMem+i+1);
    }
  }
  nColumn = n;

  /* If the DISTINCT keyword was present on the SELECT statement

  }
  if( sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0) ) return 1;
  memset(&sAggInfo, 0, sizeof(sAggInfo));

  pOrderBy = p->pOrderBy;
  if( IgnorableOrderby(pDest) ){
    p->pOrderBy = 0;

    /* In these cases the DISTINCT operator makes no difference to the
    ** results, so remove it if it were specified.
    */
    assert(pDest->eDest==SRT_Exists || pDest->eDest==SRT_Union || 
           pDest->eDest==SRT_Except || pDest->eDest==SRT_Discard);
    p->isDistinct = 0;
  }
  if( sqlite3SelectResolve(pParse, p, 0) ){
    goto select_end;
  }
  p->pOrderBy = pOrderBy;

#ifndef SQLITE_OMIT_COMPOUND_SELECT

/*
** 2001 September 15
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**    May you do good and not evil.
**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.630 2008/01/02 17:11:14 danielk1977 Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_

/*
** The macro unlikely() is a hint that surrounds a boolean
** expression that is usually false.  Macro likely() surrounds

};

/*
** The results of a select can be distributed in several ways.
*/
#define SRT_Union        1  /* Store result as keys in an index */
#define SRT_Except       2  /* Remove result from a UNION index */
#define SRT_Exists       3  /* Store 1 if the result is not empty */
#define SRT_Discard      4  /* Do not save the results anywhere */

/* The ORDER BY clause is ignored for all of the above */
#define IgnorableOrderby(X) ((X->eDest)<=SRT_Discard)

#define SRT_Callback     5  /* Invoke a callback with each row of result */
#define SRT_Mem          6  /* Store result in a memory cell */
#define SRT_Set          7  /* Store non-null results as keys in an index */
#define SRT_Table        8  /* Store result as data with an automatic rowid */
#define SRT_EphemTab     9  /* Create transient tab and store like SRT_Table */
#define SRT_Subroutine  10  /* Call a subroutine to handle results */


/*
** A structure used to customize the behaviour of sqlite3Select(). See
** comments above sqlite3Select() for details.
*/
typedef struct SelectDest SelectDest;
struct SelectDest {