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 1.228 2005/01/18 17:40:04 drh Exp $
*/
#include "sqliteInt.h"


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

/*
** Add a term to the WHERE expression in *ppExpr that requires the
** zCol column to be equal in the two tables pTab1 and pTab2.
*/
static void addWhereTerm(
  const char *zCol,        /* Name of the column */
  const Table *pTab1,      /* First table */
  const char *zAlias1,     /* Alias for first table.  May be NULL */
  const Table *pTab2,      /* Second table */
  const char *zAlias2,     /* Alias for second table.  May be NULL */
  Expr **ppExpr            /* Add the equality term to this expression */
){
  Token dummy;
  Expr *pE1a, *pE1b, *pE1c;
  Expr *pE2a, *pE2b, *pE2c;
  Expr *pE;

  setToken(&dummy, zCol);
  pE1a = sqlite3Expr(TK_ID, 0, 0, &dummy);
  pE2a = sqlite3Expr(TK_ID, 0, 0, &dummy);
  if( zAlias1==0 ){
    zAlias1 = pTab1->zName;
  }
  setToken(&dummy, zAlias1);
  pE1b = sqlite3Expr(TK_ID, 0, 0, &dummy);
  if( zAlias2==0 ){
    zAlias2 = pTab2->zName;
  }
  setToken(&dummy, zAlias2);
  pE2b = sqlite3Expr(TK_ID, 0, 0, &dummy);
  pE1c = sqlite3Expr(TK_DOT, pE1b, pE1a, 0);
  pE2c = sqlite3Expr(TK_DOT, pE2b, pE2a, 0);
  pE = sqlite3Expr(TK_EQ, pE1c, pE2c, 0);
  ExprSetProperty(pE, EP_FromJoin);
  *ppExpr = sqlite3ExprAnd(*ppExpr, pE);
}

        sqlite3ErrorMsg(pParse, "a NATURAL join may not have "
           "an ON or USING clause", 0);
        return 1;
      }
      for(j=0; j<pLeftTab->nCol; j++){
        char *zName = pLeftTab->aCol[j].zName;
        if( columnIndex(pRightTab, zName)>=0 ){
          addWhereTerm(zName, pLeftTab, pLeft->zAlias, 
                              pRightTab, pRight->zAlias, &p->pWhere);
        }
      }
    }

    /* Disallow both ON and USING clauses in the same join
    */
    if( pLeft->pOn && pLeft->pUsing ){

      for(j=0; j<pList->nId; j++){
        char *zName = pList->a[j].zName;
        if( columnIndex(pLeftTab, zName)<0 || columnIndex(pRightTab, zName)<0 ){
          sqlite3ErrorMsg(pParse, "cannot join using column %s - column "
            "not present in both tables", zName);
          return 1;
        }
        addWhereTerm(zName, pLeftTab, pLeft->zAlias, 
                            pRightTab, pRight->zAlias, &p->pWhere);
      }
    }
  }
  return 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 1.15 2005/01/18 17:40:04 drh Exp $

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

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

  }
} {a 1 b 2 c 3 d 4 a 2 b 3 c 4 d 5}
do_test join-1.3.1 {
  execsql2 {
    SELECT * FROM t2 NATURAL JOIN t1;
  }
} {b 2 c 3 d 4 a 1 b 3 c 4 d 5 a 2}
do_test join-1.3.2 {
  execsql2 {
    SELECT * FROM t2 AS x NATURAL JOIN t1;
  }
} {b 2 c 3 d 4 a 1 b 3 c 4 d 5 a 2}
do_test join-1.3.3 {
  execsql2 {
    SELECT * FROM t2 NATURAL JOIN t1 AS y;
  }
} {b 2 c 3 d 4 a 1 b 3 c 4 d 5 a 2}
do_test join-1.4.1 {
  execsql2 {
    SELECT * FROM t1 INNER JOIN t2 USING(b,c);
  }
} {a 1 b 2 c 3 d 4 a 2 b 3 c 4 d 5}
do_test join-1.4.2 {
  execsql2 {
    SELECT * FROM t1 AS x INNER JOIN t2 USING(b,c);
  }
} {a 1 b 2 c 3 d 4 a 2 b 3 c 4 d 5}
do_test join-1.4.3 {
  execsql2 {
    SELECT * FROM t1 INNER JOIN t2 AS y USING(b,c);
  }
} {a 1 b 2 c 3 d 4 a 2 b 3 c 4 d 5}
do_test join-1.4.4 {
  execsql2 {
    SELECT * FROM t1 AS x INNER JOIN t2 AS y USING(b,c);
  }
} {a 1 b 2 c 3 d 4 a 2 b 3 c 4 d 5}
do_test join-1.5 {
  execsql2 {
    SELECT * FROM t1 INNER JOIN t2 USING(b);
  }
} {a 1 b 2 c 3 c 3 d 4 a 2 b 3 c 4 c 4 d 5}
do_test join-1.6 {