SQLite

**    May you share freely, never taking more than you give.
**
*************************************************************************
** This module contains C code that generates VDBE code used to process
** the WHERE clause of SQL statements.  Also found here are subroutines
** to generate VDBE code to evaluate expressions.
**
** $Id: where.c,v 1.65 2002/09/30 12:36:26 drh Exp $
*/
#include "sqliteInt.h"

/*
** The query generator uses an array of instances of this structure to
** help it analyze the subexpressions of the WHERE clause.  Each WHERE
** clause subexpression is separated from the others by an AND operator.

    /* Check to see if there is an expression that uses only the
    ** ROWID field of this table.  For terms of the form ROWID==expr
    ** set iDirectEq[i] to the index of the term.  For terms of the
    ** form ROWID<expr or ROWID<=expr set iDirectLt[i] to the term index.
    ** For terms like ROWID>expr or ROWID>=expr set iDirectGt[i].
    */
    pWInfo->a[i].iCur = -1;
    iDirectEq[i] = -1;
    iDirectLt[i] = -1;
    iDirectGt[i] = -1;
    for(j=0; j<nExpr; j++){
      if( aExpr[j].idxLeft==idx && aExpr[j].p->pLeft->iColumn<0
            && (aExpr[j].prereqRight & loopMask)==aExpr[j].prereqRight ){
        switch( aExpr[j].p->op ){

    }
    pWInfo->a[i].pIdx = pBestIdx;
    pWInfo->a[i].score = bestScore;
    loopMask |= 1<<idx;
    if( pBestIdx ){
      pWInfo->a[i].iCur = pParse->nTab++;
      pWInfo->peakNTab = pParse->nTab;


    }
  }

  /* Check to see if the ORDER BY clause is or can be satisfied by the
  ** use of an index on the first table.
  */
  if( ppOrderBy && *ppOrderBy && pTabList->nSrc>0 ){

#    May you share freely, never taking more than you give.
#
#***********************************************************************
# This file implements regression tests for SQLite library.
#
# This file implements tests for joins, including outer joins.
#
# $Id: join.test,v 1.6 2002/09/30 12:36:26 drh Exp $

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

do_test join-1.1 {
  execsql {
    CREATE TABLE t1(a,b,c);

} {}
do_test join-4.10 {
  execsql {
    SELECT * FROM t6, t5 WHERE t6.a>t5.a;
  }
} {}

do_test join-5.1 {
  execsql {
    BEGIN;
    create table centros (id integer primary key, centro);
    INSERT INTO centros VALUES(1,'xxx');
    create table usuarios (id integer primary key, nombre, apellidos,
    idcentro integer);
    INSERT INTO usuarios VALUES(1,'a','aa',1);
    INSERT INTO usuarios VALUES(2,'b','bb',1);
    INSERT INTO usuarios VALUES(3,'c','cc',NULL);
    create index idcentro on usuarios (idcentro);
    END;
    select usuarios.id, usuarios.nombre, centros.centro from
    usuarios left outer join centros on usuarios.idcentro = centros.id;
  }
} {1 a xxx 2 b xxx 3 c {}}

finish_test