memset(&sSrc, 0, sizeof(sSrc));
    sSrc.nSrc = 1;
    sSrc.a[0].zName = p->zName;
    sSrc.a[0].pTab = p;
    sSrc.a[0].iCursor = -1;
    sNC.pParse = pParse;
    sNC.pSrcList = &sSrc;
    sNC.isCheck = 1;
    pList = p->pCheck;
    for(i=0; i<pList->nExpr; i++){
      if( sqlite3ResolveExprNames(&sNC, pList->a[i].pExpr) ){
        return;
      }
    }
  }

    memset(&sSrc, 0, sizeof(sSrc));
    sSrc.nSrc = 1;
    sSrc.a[0].zName = p->zName;
    sSrc.a[0].pTab = p;
    sSrc.a[0].iCursor = -1;
    sNC.pParse = pParse;
    sNC.pSrcList = &sSrc;
    sNC.ncFlags = NC_IsCheck;
    pList = p->pCheck;
    for(i=0; i<pList->nExpr; i++){
      if( sqlite3ResolveExprNames(&sNC, pList->a[i].pExpr) ){
        return;
      }
    }
  }

        char *zAs = pEList->a[j].zName;
        if( zAs!=0 && sqlite3StrICmp(zAs, zCol)==0 ){
          Expr *pOrig;
          assert( pExpr->pLeft==0 && pExpr->pRight==0 );
          assert( pExpr->x.pList==0 );
          assert( pExpr->x.pSelect==0 );
          pOrig = pEList->a[j].pExpr;
          if( !pNC->allowAgg && ExprHasProperty(pOrig, EP_Agg) ){
            sqlite3ErrorMsg(pParse, "misuse of aliased aggregate %s", zAs);
            return WRC_Abort;
          }
          resolveAlias(pParse, pEList, j, pExpr, "");
          cnt = 1;
          pMatch = 0;
          assert( zTab==0 && zDb==0 );
................................................................................
            pNC->nErr++;
          }
          pExpr->op = TK_NULL;
          return WRC_Prune;
        }
      }
#endif
      if( is_agg && !pNC->allowAgg ){
        sqlite3ErrorMsg(pParse, "misuse of aggregate function %.*s()", nId,zId);
        pNC->nErr++;
        is_agg = 0;
      }else if( no_such_func ){
        sqlite3ErrorMsg(pParse, "no such function: %.*s", nId, zId);
        pNC->nErr++;
      }else if( wrong_num_args ){
        sqlite3ErrorMsg(pParse,"wrong number of arguments to function %.*s()",
             nId, zId);
        pNC->nErr++;
      }
      if( is_agg ){
        pExpr->op = TK_AGG_FUNCTION;
        pNC->hasAgg = 1;
      }
      if( is_agg ) pNC->allowAgg = 0;
      sqlite3WalkExprList(pWalker, pList);
      if( is_agg ) pNC->allowAgg = 1;
      /* FIX ME:  Compute pExpr->affinity based on the expected return
      ** type of the function 
      */
      return WRC_Prune;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_SELECT:
................................................................................
    case TK_EXISTS:  testcase( pExpr->op==TK_EXISTS );
#endif
    case TK_IN: {
      testcase( pExpr->op==TK_IN );
      if( ExprHasProperty(pExpr, EP_xIsSelect) ){
        int nRef = pNC->nRef;
#ifndef SQLITE_OMIT_CHECK
        if( pNC->isCheck ){
          sqlite3ErrorMsg(pParse,"subqueries prohibited in CHECK constraints");
        }
#endif
        sqlite3WalkSelect(pWalker, pExpr->x.pSelect);
        assert( pNC->nRef>=nRef );
        if( nRef!=pNC->nRef ){
          ExprSetProperty(pExpr, EP_VarSelect);
        }
      }
      break;
    }
#ifndef SQLITE_OMIT_CHECK
    case TK_VARIABLE: {
      if( pNC->isCheck ){
        sqlite3ErrorMsg(pParse,"parameters prohibited in CHECK constraints");
      }
      break;
    }
#endif
  }
  return (pParse->nErr || pParse->db->mallocFailed) ? WRC_Abort : WRC_Continue;
................................................................................

  /* Resolve all names in the ORDER BY term expression
  */
  memset(&nc, 0, sizeof(nc));
  nc.pParse = pParse;
  nc.pSrcList = pSelect->pSrc;
  nc.pEList = pEList;
  nc.allowAgg = 1;
  nc.nErr = 0;
  db = pParse->db;
  savedSuppErr = db->suppressErr;
  db->suppressErr = 1;
  rc = sqlite3ResolveExprNames(&nc, pE);
  db->suppressErr = savedSuppErr;
  if( rc ) return 0;
................................................................................
        sqlite3ResolveExprNames(&sNC, p->pOffset) ){
      return WRC_Abort;
    }
  
    /* Set up the local name-context to pass to sqlite3ResolveExprNames() to
    ** resolve the result-set expression list.
    */
    sNC.allowAgg = 1;
    sNC.pSrcList = p->pSrc;
    sNC.pNext = pOuterNC;
  
    /* Resolve names in the result set. */
    pEList = p->pEList;
    assert( pEList!=0 );
    for(i=0; i<pEList->nExpr; i++){
................................................................................
    }
  
    /* If there are no aggregate functions in the result-set, and no GROUP BY 
    ** expression, do not allow aggregates in any of the other expressions.
    */
    assert( (p->selFlags & SF_Aggregate)==0 );
    pGroupBy = p->pGroupBy;
    if( pGroupBy || sNC.hasAgg ){
      p->selFlags |= SF_Aggregate;
    }else{
      sNC.allowAgg = 0;
    }
  
    /* If a HAVING clause is present, then there must be a GROUP BY clause.
    */
    if( p->pHaving && !pGroupBy ){
      sqlite3ErrorMsg(pParse, "a GROUP BY clause is required before HAVING");
      return WRC_Abort;
................................................................................
      return WRC_Abort;
    }

    /* The ORDER BY and GROUP BY clauses may not refer to terms in
    ** outer queries 
    */
    sNC.pNext = 0;
    sNC.allowAgg = 1;

    /* Process the ORDER BY clause for singleton SELECT statements.
    ** The ORDER BY clause for compounds SELECT statements is handled
    ** below, after all of the result-sets for all of the elements of
    ** the compound have been resolved.
    */
    if( !isCompound && resolveOrderGroupBy(&sNC, p, p->pOrderBy, "ORDER") ){
................................................................................
**
** The "x" term of the order by is replaced by "a+b" to render:
**
**      SELECT a+b AS x, c+d AS y FROM t1 ORDER BY a+b;
**
** Function calls are checked to make sure that the function is 
** defined and that the correct number of arguments are specified.
** If the function is an aggregate function, then the pNC->hasAgg is
** set and the opcode is changed from TK_FUNCTION to TK_AGG_FUNCTION.
** If an expression contains aggregate functions then the EP_Agg
** property on the expression is set.
**
** An error message is left in pParse if anything is amiss.  The number
** if errors is returned.
*/
int sqlite3ResolveExprNames( 
  NameContext *pNC,       /* Namespace to resolve expressions in. */
  Expr *pExpr             /* The expression to be analyzed. */
){
  int savedHasAgg;
  Walker w;

  if( pExpr==0 ) return 0;
#if SQLITE_MAX_EXPR_DEPTH>0
  {
    Parse *pParse = pNC->pParse;
    if( sqlite3ExprCheckHeight(pParse, pExpr->nHeight+pNC->pParse->nHeight) ){
      return 1;
    }
    pParse->nHeight += pExpr->nHeight;
  }
#endif
  savedHasAgg = pNC->hasAgg;
  pNC->hasAgg = 0;
  w.xExprCallback = resolveExprStep;
  w.xSelectCallback = resolveSelectStep;
  w.pParse = pNC->pParse;
  w.u.pNC = pNC;
  sqlite3WalkExpr(&w, pExpr);
#if SQLITE_MAX_EXPR_DEPTH>0
  pNC->pParse->nHeight -= pExpr->nHeight;
#endif
  if( pNC->nErr>0 || w.pParse->nErr>0 ){
    ExprSetProperty(pExpr, EP_Error);
  }
  if( pNC->hasAgg ){
    ExprSetProperty(pExpr, EP_Agg);
  }else if( savedHasAgg ){
    pNC->hasAgg = 1;
  }
  return ExprHasProperty(pExpr, EP_Error);
}


/*
** Resolve all names in all expressions of a SELECT and in all

        char *zAs = pEList->a[j].zName;
        if( zAs!=0 && sqlite3StrICmp(zAs, zCol)==0 ){
          Expr *pOrig;
          assert( pExpr->pLeft==0 && pExpr->pRight==0 );
          assert( pExpr->x.pList==0 );
          assert( pExpr->x.pSelect==0 );
          pOrig = pEList->a[j].pExpr;
          if( (pNC->ncFlags&NC_AllowAgg)==0 && ExprHasProperty(pOrig, EP_Agg) ){
            sqlite3ErrorMsg(pParse, "misuse of aliased aggregate %s", zAs);
            return WRC_Abort;
          }
          resolveAlias(pParse, pEList, j, pExpr, "");
          cnt = 1;
          pMatch = 0;
          assert( zTab==0 && zDb==0 );
................................................................................
            pNC->nErr++;
          }
          pExpr->op = TK_NULL;
          return WRC_Prune;
        }
      }
#endif
      if( is_agg && (pNC->ncFlags & NC_AllowAgg)==0 ){
        sqlite3ErrorMsg(pParse, "misuse of aggregate function %.*s()", nId,zId);
        pNC->nErr++;
        is_agg = 0;
      }else if( no_such_func ){
        sqlite3ErrorMsg(pParse, "no such function: %.*s", nId, zId);
        pNC->nErr++;
      }else if( wrong_num_args ){
        sqlite3ErrorMsg(pParse,"wrong number of arguments to function %.*s()",
             nId, zId);
        pNC->nErr++;
      }
      if( is_agg ){
        pExpr->op = TK_AGG_FUNCTION;
        pNC->ncFlags |= NC_HasAgg;
      }
      if( is_agg ) pNC->ncFlags &= ~NC_AllowAgg;
      sqlite3WalkExprList(pWalker, pList);
      if( is_agg ) pNC->ncFlags |= NC_AllowAgg;
      /* FIX ME:  Compute pExpr->affinity based on the expected return
      ** type of the function 
      */
      return WRC_Prune;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_SELECT:
................................................................................
    case TK_EXISTS:  testcase( pExpr->op==TK_EXISTS );
#endif
    case TK_IN: {
      testcase( pExpr->op==TK_IN );
      if( ExprHasProperty(pExpr, EP_xIsSelect) ){
        int nRef = pNC->nRef;
#ifndef SQLITE_OMIT_CHECK
        if( (pNC->ncFlags & NC_IsCheck)!=0 ){
          sqlite3ErrorMsg(pParse,"subqueries prohibited in CHECK constraints");
        }
#endif
        sqlite3WalkSelect(pWalker, pExpr->x.pSelect);
        assert( pNC->nRef>=nRef );
        if( nRef!=pNC->nRef ){
          ExprSetProperty(pExpr, EP_VarSelect);
        }
      }
      break;
    }
#ifndef SQLITE_OMIT_CHECK
    case TK_VARIABLE: {
      if( (pNC->ncFlags & NC_IsCheck)!=0 ){
        sqlite3ErrorMsg(pParse,"parameters prohibited in CHECK constraints");
      }
      break;
    }
#endif
  }
  return (pParse->nErr || pParse->db->mallocFailed) ? WRC_Abort : WRC_Continue;
................................................................................

  /* Resolve all names in the ORDER BY term expression
  */
  memset(&nc, 0, sizeof(nc));
  nc.pParse = pParse;
  nc.pSrcList = pSelect->pSrc;
  nc.pEList = pEList;
  nc.ncFlags = NC_AllowAgg;
  nc.nErr = 0;
  db = pParse->db;
  savedSuppErr = db->suppressErr;
  db->suppressErr = 1;
  rc = sqlite3ResolveExprNames(&nc, pE);
  db->suppressErr = savedSuppErr;
  if( rc ) return 0;
................................................................................
        sqlite3ResolveExprNames(&sNC, p->pOffset) ){
      return WRC_Abort;
    }
  
    /* Set up the local name-context to pass to sqlite3ResolveExprNames() to
    ** resolve the result-set expression list.
    */
    sNC.ncFlags = NC_AllowAgg;
    sNC.pSrcList = p->pSrc;
    sNC.pNext = pOuterNC;
  
    /* Resolve names in the result set. */
    pEList = p->pEList;
    assert( pEList!=0 );
    for(i=0; i<pEList->nExpr; i++){
................................................................................
    }
  
    /* If there are no aggregate functions in the result-set, and no GROUP BY 
    ** expression, do not allow aggregates in any of the other expressions.
    */
    assert( (p->selFlags & SF_Aggregate)==0 );
    pGroupBy = p->pGroupBy;
    if( pGroupBy || (sNC.ncFlags & NC_HasAgg)!=0 ){
      p->selFlags |= SF_Aggregate;
    }else{
      sNC.ncFlags &= ~NC_AllowAgg;
    }
  
    /* If a HAVING clause is present, then there must be a GROUP BY clause.
    */
    if( p->pHaving && !pGroupBy ){
      sqlite3ErrorMsg(pParse, "a GROUP BY clause is required before HAVING");
      return WRC_Abort;
................................................................................
      return WRC_Abort;
    }

    /* The ORDER BY and GROUP BY clauses may not refer to terms in
    ** outer queries 
    */
    sNC.pNext = 0;
    sNC.ncFlags |= NC_AllowAgg;

    /* Process the ORDER BY clause for singleton SELECT statements.
    ** The ORDER BY clause for compounds SELECT statements is handled
    ** below, after all of the result-sets for all of the elements of
    ** the compound have been resolved.
    */
    if( !isCompound && resolveOrderGroupBy(&sNC, p, p->pOrderBy, "ORDER") ){
................................................................................
**
** The "x" term of the order by is replaced by "a+b" to render:
**
**      SELECT a+b AS x, c+d AS y FROM t1 ORDER BY a+b;
**
** Function calls are checked to make sure that the function is 
** defined and that the correct number of arguments are specified.
** If the function is an aggregate function, then the NC_HasAgg flag is
** set and the opcode is changed from TK_FUNCTION to TK_AGG_FUNCTION.
** If an expression contains aggregate functions then the EP_Agg
** property on the expression is set.
**
** An error message is left in pParse if anything is amiss.  The number
** if errors is returned.
*/
int sqlite3ResolveExprNames( 
  NameContext *pNC,       /* Namespace to resolve expressions in. */
  Expr *pExpr             /* The expression to be analyzed. */
){
  u8 savedHasAgg;
  Walker w;

  if( pExpr==0 ) return 0;
#if SQLITE_MAX_EXPR_DEPTH>0
  {
    Parse *pParse = pNC->pParse;
    if( sqlite3ExprCheckHeight(pParse, pExpr->nHeight+pNC->pParse->nHeight) ){
      return 1;
    }
    pParse->nHeight += pExpr->nHeight;
  }
#endif
  savedHasAgg = pNC->ncFlags & NC_HasAgg;
  pNC->ncFlags &= ~NC_HasAgg;
  w.xExprCallback = resolveExprStep;
  w.xSelectCallback = resolveSelectStep;
  w.pParse = pNC->pParse;
  w.u.pNC = pNC;
  sqlite3WalkExpr(&w, pExpr);
#if SQLITE_MAX_EXPR_DEPTH>0
  pNC->pParse->nHeight -= pExpr->nHeight;
#endif
  if( pNC->nErr>0 || w.pParse->nErr>0 ){
    ExprSetProperty(pExpr, EP_Error);
  }
  if( pNC->ncFlags & NC_HasAgg ){
    ExprSetProperty(pExpr, EP_Agg);
  }else if( savedHasAgg ){
    pNC->ncFlags |= NC_HasAgg;
  }
  return ExprHasProperty(pExpr, EP_Error);
}


/*
** Resolve all names in all expressions of a SELECT and in all

  }
  pTab = p->pSrc->a[0].pTab;
  pExpr = p->pEList->a[0].pExpr;
  assert( pTab && !pTab->pSelect && pExpr );

  if( IsVirtual(pTab) ) return 0;
  if( pExpr->op!=TK_AGG_FUNCTION ) return 0;

  if( (pAggInfo->aFunc[0].pFunc->flags&SQLITE_FUNC_COUNT)==0 ) return 0;
  if( pExpr->flags&EP_Distinct ) return 0;

  return pTab;
}

/*

  }
  pTab = p->pSrc->a[0].pTab;
  pExpr = p->pEList->a[0].pExpr;
  assert( pTab && !pTab->pSelect && pExpr );

  if( IsVirtual(pTab) ) return 0;
  if( pExpr->op!=TK_AGG_FUNCTION ) return 0;
  if( pAggInfo->nFunc==0 ) return 0;
  if( (pAggInfo->aFunc[0].pFunc->flags&SQLITE_FUNC_COUNT)==0 ) return 0;
  if( pExpr->flags&EP_Distinct ) return 0;

  return pTab;
}

/*

** NameContext list corresponds to searching through successively outer
** subqueries looking for a match.
*/
struct NameContext {
  Parse *pParse;       /* The parser */
  SrcList *pSrcList;   /* One or more tables used to resolve names */
  ExprList *pEList;    /* Optional list of named expressions */


  int nRef;            /* Number of names resolved by this context */
  int nErr;            /* Number of errors encountered while resolving names */
  u8 allowAgg;         /* Aggregate functions allowed here */
  u8 hasAgg;           /* True if aggregates are seen */
  u8 isCheck;          /* True if resolving names in a CHECK constraint */
  AggInfo *pAggInfo;   /* Information about aggregates at this level */
  NameContext *pNext;  /* Next outer name context.  NULL for outermost */
};








/*
** An instance of the following structure contains all information
** needed to generate code for a single SELECT statement.
**
** nLimit is set to -1 if there is no LIMIT clause.  nOffset is set to 0.
** If there is a LIMIT clause, the parser sets nLimit to the value of the
** limit and nOffset to the value of the offset (or 0 if there is not

** NameContext list corresponds to searching through successively outer
** subqueries looking for a match.
*/
struct NameContext {
  Parse *pParse;       /* The parser */
  SrcList *pSrcList;   /* One or more tables used to resolve names */
  ExprList *pEList;    /* Optional list of named expressions */
  AggInfo *pAggInfo;   /* Information about aggregates at this level */
  NameContext *pNext;  /* Next outer name context.  NULL for outermost */
  int nRef;            /* Number of names resolved by this context */
  int nErr;            /* Number of errors encountered while resolving names */


  u8 ncFlags;          /* Zero or more NC_* flags defined below */


};

/*
** Allowed values for the NameContext, ncFlags field.
*/
#define NC_AllowAgg  0x01    /* Aggregate functions are allowed here */
#define NC_HasAgg    0x02    /* One or more aggregate functions seen */
#define NC_IsCheck   0x04    /* True if resolving names in a CHECK constraint */

/*
** An instance of the following structure contains all information
** needed to generate code for a single SELECT statement.
**
** nLimit is set to -1 if there is no LIMIT clause.  nOffset is set to 0.
** If there is a LIMIT clause, the parser sets nLimit to the value of the
** limit and nOffset to the value of the offset (or 0 if there is not