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 1.144 2003/07/19 00:44:14 drh Exp $
*/
#include "sqliteInt.h"


/*
** Allocate a new Select structure and return a pointer to that
** structure.

    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
      assert( pIdx->nColumn>=1 );
      if( pIdx->aiColumn[0]==iCol ) break;
    }
    if( pIdx==0 ) return 0;
  }

  /* Identify column types if we will be using the callback.  This
  ** step is skipped if the output is going to a table or a memory cell.
  ** The column names have already been generated in the calling function.
  */
  v = sqliteGetVdbe(pParse);
  if( v==0 ) return 0;
  if( eDest==SRT_Callback ){

    generateColumnTypes(pParse, p->pSrc, p->pEList);
  }

  /* Generating code to find the min or the max.  Basically all we have
  ** to do is find the first or the last entry in the chosen index.  If
  ** the min() or max() is on the INTEGER PRIMARY KEY, then find the first
  ** or last entry in the main table.

             "between 1 and %d", iCol, pEList->nExpr);
          goto select_end;
        }
      }
    }
  }









  /* Begin generating code.
  */
  v = sqliteGetVdbe(pParse);
  if( v==0 ) goto select_end;

  /* Identify column names if we will be using them in a callback.  This
  ** step is skipped if the output is going to some other destination.

  }else{
    int iMem = pParse->nMem++;
    if( iMem==0 ) iMem = pParse->nMem++;
    sqliteVdbeAddOp(v, OP_Integer, -p->nOffset, 0);
    sqliteVdbeAddOp(v, OP_MemStore, iMem, 1);
    p->nOffset = iMem;
  }

  /* Check for the special case of a min() or max() function by itself
  ** in the result set.
  */
  if( simpleMinMaxQuery(pParse, p, eDest, iParm) ){
    rc = 0;
    goto select_end;
  }

  /* Generate code for all sub-queries in the FROM clause
  */
  for(i=0; i<pTabList->nSrc; i++){
    const char *zSavedAuthContext;
    int needRestoreContext;

    if( isAgg ) *pParentAgg = 1;
    return rc;
  }

  /* Identify column types if we will be using a callback.  This
  ** step is skipped if the output is going to a destination other
  ** than a callback.
  **
  ** We have to do this separately from the creation of column names
  ** above because if the pTabList contains views then they will not
  ** have been resolved and we will not know the column types until
  ** now.
  */
  if( eDest==SRT_Callback ){
    generateColumnTypes(pParse, pTabList, pEList);
  }

  /* If the output is destined for a temporary table, open that table.
  */

#
#***********************************************************************
# This file implements regression tests for SQLite library.  The
# focus of this file is testing SELECT statements that contain
# aggregate min() and max() functions and which are handled as
# as a special case.
#
# $Id: minmax.test,v 1.6 2003/07/19 00:44:15 drh Exp $

set testdir [file dirname $argv0]
source $testdir/tester.tcl

do_test minmax-1.0 {
  execsql {
    BEGIN;

  }
} {999}
do_test minmax-5.5 {
  execsql {
    SELECT coalesce(max(rowid),999) FROM t3 WHERE rowid<25;
  }
} {999}

# Make sure the min(x) and max(x) optimizations work when there
# is a LIMIT clause.  Ticket #396.
#
do_test minmax-6.1 {
  execsql {
    SELECT min(a) FROM t2 LIMIT 1
  }
} {1}
do_test minmax-6.2 {
  execsql {
    SELECT max(a) FROM t2 LIMIT 3
  }
} {22}
do_test minmax-6.3 {
  execsql {
    SELECT min(a) FROM t2 LIMIT 0,100
  }
} {1}
do_test minmax-6.4 {
  execsql {
    SELECT max(a) FROM t2 LIMIT 1,100
  }
} {}
do_test minmax-6.5 {
  execsql {
    SELECT min(x) FROM t3 LIMIT 1
  }
} {{}}
do_test minmax-6.6 {
  execsql {
    SELECT max(x) FROM t3 LIMIT 0
  }
} {}
do_test minmax-6.7 {
  execsql {
    SELECT max(a) FROM t2 LIMIT 0
  }
} {}


finish_test