SQLite

  /* Delete the Table structure itself.
  */
  sqlite3DeleteColumnNames(db, pTable);
  sqlite3DbFree(db, pTable->zName);
  sqlite3DbFree(db, pTable->zColAff);
  sqlite3SelectDelete(db, pTable->pSelect);

  sqlite3ExprListDelete(db, pTable->pCheck);

#ifndef SQLITE_OMIT_VIRTUALTABLE
  sqlite3VtabClear(db, pTable);
#endif
  sqlite3DbFree(db, pTable);

  /* Verify that no lookaside memory was used by schema tables */
  assert( nLookaside==0 || nLookaside==db->lookaside.nOut );

  DbFixer sFix;        /* For assigning database names to pTable */
  int sortOrderMask;   /* 1 to honor DESC in index.  0 to ignore. */
  sqlite3 *db = pParse->db;
  Db *pDb;             /* The specific table containing the indexed database */
  int iDb;             /* Index of the database that is being written */
  Token *pName = 0;    /* Unqualified name of the index to create */
  struct ExprList_item *pListItem; /* For looping over pList */

  int nExtra = 0;                  /* Space allocated for zExtra[] */
  int nExtraCol;                   /* Number of extra columns needed */
  char *zExtra = 0;                /* Extra space after the Index object */
  Index *pPk = 0;      /* PRIMARY KEY index for WITHOUT ROWID tables */

  if( db->mallocFailed || IN_DECLARE_VTAB || pParse->nErr>0 ){
    goto exit_create_index;

  ** TODO:  Add a test to make sure that the same column is not named
  ** more than once within the same index.  Only the first instance of
  ** the column will ever be used by the optimizer.  Note that using the
  ** same column more than once cannot be an error because that would 
  ** break backwards compatibility - it needs to be a warning.
  */
  for(i=0, pListItem=pList->a; i<pList->nExpr; i++, pListItem++){

    Expr *pCExpr;
    int requestedSortOrder;
    char *zColl;                   /* Collation sequence name */

    sqlite3ResolveSelfReference(pParse, pTab, NC_IdxExpr, pListItem->pExpr, 0);
    if( pParse->nErr ) goto exit_create_index;
    pCExpr = sqlite3ExprSkipCollate(pListItem->pExpr);
    if( pCExpr->op!=TK_COLUMN ){
      sqlite3ErrorMsg(pParse, "indexes on expressions not yet supported");
      continue;
    }
    j = pCExpr->iColumn;









    assert( j<=0x7fff );
    if( j<0 ) j = pTab->iPKey;
    pIndex->aiColumn[i] = (i16)j;
    zColl = 0;
    if( pListItem->pExpr->op==TK_COLLATE ){
      int nColl;
      zColl = pListItem->pExpr->u.zToken;
      nColl = sqlite3Strlen30(zColl) + 1;
      assert( nExtra>=nColl );
      memcpy(zExtra, zColl, nColl);
      zColl = zExtra;
      zExtra += nColl;
      nExtra -= nColl;
    }else if( j>=0 ){
      zColl = pTab->aCol[j].zColl;

    }
    if( !zColl ) zColl = "BINARY";
    if( !db->init.busy && !sqlite3LocateCollSeq(pParse, zColl) ){
      goto exit_create_index;
    }
    pIndex->azColl[i] = zColl;
    requestedSortOrder = pListItem->sortOrder & sortOrderMask;
    pIndex->aSortOrder[i] = (u8)requestedSortOrder;
    if( pTab->aCol[j].notNull==0 ) pIndex->uniqNotNull = 0;

    }
    ExprSetProperty(p, EP_Resolved);
  }
  return p;
}

/*
** Report an error that an expression is not valid for some set of
** pNC->ncFlags values determined by validMask.  If 
*/
static void notValid(
  Parse *pParse,       /* Leave error message here */
  NameContext *pNC,    /* The name context */
  const char *zMsg,    /* Type of error */
  int validMask,       /* Set of contexts for which prohibited */
  int okForInit        /* No error if pParse->db->init.busy is true */
){
  assert( (validMask&~(NC_IsCheck|NC_PartIdx|NC_IdxExpr))==0 );
  if( (pNC->ncFlags & validMask)!=0 
   && (pParse->db->init.busy==0 || !okForInit)
  ){
    const char *zIn = "partial index WHERE clauses";



    if( pNC->ncFlags & NC_IdxExpr )      zIn = "index expressions";
#ifndef SQLITE_OMIT_CHECK








    else if( pNC->ncFlags & NC_IsCheck ) zIn = "CHECK constraints";
#endif
    sqlite3ErrorMsg(pParse, "%s prohibited in %s", zMsg, zIn);
  }
}




/*
** Expression p should encode a floating point value between 1.0 and 0.0.
** Return 1024 times this value.  Or return -1 if p is not a floating point
** value between 1.0 and 0.0.
*/
static int exprProbability(Expr *p){

    case TK_DOT: {
      const char *zColumn;
      const char *zTable;
      const char *zDb;
      Expr *pRight;

      /* if( pSrcList==0 ) break; */
      notValid(pParse, pNC, "the \".\" operator", NC_IdxExpr, 0);
      notValid(pParse, pNC, "the \".\" operator", NC_PartIdx|NC_IsCheck, 1);
      pRight = pExpr->pRight;
      if( pRight->op==TK_ID ){
        zDb = 0;
        zTable = pExpr->pLeft->u.zToken;
        zColumn = pRight->u.zToken;
      }else{
        assert( pRight->op==TK_DOT );

      int auth;                   /* Authorization to use the function */
      int nId;                    /* Number of characters in function name */
      const char *zId;            /* The function name. */
      FuncDef *pDef;              /* Information about the function */
      u8 enc = ENC(pParse->db);   /* The database encoding */

      assert( !ExprHasProperty(pExpr, EP_xIsSelect) );
      notValid(pParse, pNC, "functions", NC_PartIdx, 0);
      zId = pExpr->u.zToken;
      nId = sqlite3Strlen30(zId);
      pDef = sqlite3FindFunction(pParse->db, zId, nId, n, enc, 0);
      if( pDef==0 ){
        pDef = sqlite3FindFunction(pParse->db, zId, nId, -2, enc, 0);
        if( pDef==0 ){
          no_such_func = 1;

          }
          pExpr->op = TK_NULL;
          return WRC_Prune;
        }
#endif
        if( pDef->funcFlags & SQLITE_FUNC_CONSTANT ){
          ExprSetProperty(pExpr,EP_ConstFunc);
        }else{
          notValid(pParse, pNC, "non-deterministic functions", NC_IdxExpr, 0);
        }
      }
      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 && pParse->db->init.busy==0 ){

    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;

        notValid(pParse, pNC, "subqueries", NC_IsCheck|NC_PartIdx|NC_IdxExpr,0);
        sqlite3WalkSelect(pWalker, pExpr->x.pSelect);
        assert( pNC->nRef>=nRef );
        if( nRef!=pNC->nRef ){
          ExprSetProperty(pExpr, EP_VarSelect);
        }
      }
      break;
    }
    case TK_VARIABLE: {

      notValid(pParse, pNC, "parameters", NC_IsCheck|NC_PartIdx|NC_IdxExpr, 0);
      break;
    }
  }
  return (pParse->nErr || pParse->db->mallocFailed) ? WRC_Abort : WRC_Continue;
}

/*

** is set to -1 and the Expr.iColumn value is set to the column number.
**
** Any errors cause an error message to be set in pParse.
*/
void sqlite3ResolveSelfReference(
  Parse *pParse,      /* Parsing context */
  Table *pTab,        /* The table being referenced */
  int type,           /* NC_IsCheck or NC_PartIdx or NC_IdxExpr */
  Expr *pExpr,        /* Expression to resolve.  May be NULL. */
  ExprList *pList     /* Expression list to resolve.  May be NUL. */
){
  SrcList sSrc;                   /* Fake SrcList for pParse->pNewTable */
  NameContext sNC;                /* Name context for pParse->pNewTable */

  assert( type==NC_IsCheck || type==NC_PartIdx || type==NC_IdxExpr );
  memset(&sNC, 0, sizeof(sNC));
  memset(&sSrc, 0, sizeof(sSrc));
  sSrc.nSrc = 1;
  sSrc.a[0].zName = pTab->zName;
  sSrc.a[0].pTab = pTab;
  sSrc.a[0].iCursor = -1;
  sNC.pParse = pParse;
  sNC.pSrcList = &sSrc;
  sNC.ncFlags = type;
  if( sqlite3ResolveExprNames(&sNC, pExpr) ) return;
  if( pList ) sqlite3ResolveExprListNames(&sNC, pList);
}

** 
*/
#define NC_AllowAgg  0x0001  /* Aggregate functions are allowed here */
#define NC_HasAgg    0x0002  /* One or more aggregate functions seen */
#define NC_IsCheck   0x0004  /* True if resolving names in a CHECK constraint */
#define NC_InAggFunc 0x0008  /* True if analyzing arguments to an agg func */
#define NC_PartIdx   0x0010  /* True if resolving a partial index WHERE */
#define NC_IdxExpr   0x0020  /* True if resolving columns of CREATE INDEX */
#define NC_MinMaxAgg 0x1000  /* min/max aggregates seen.  See note above */

/*
** 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.