SQLite

  }
  if( op==TK_SELECT_COLUMN ){
    assert( pExpr->pLeft->flags&EP_xIsSelect );
    return sqlite3ExprAffinity(
        pExpr->pLeft->x.pSelect->pEList->a[pExpr->iColumn].pExpr
    );
  }
  return pExpr->affExpr;
}

/*
** Set the collating sequence for expression pExpr to be the collating
** sequence named by pToken.   Return a pointer to a new Expr node that
** implements the COLLATE operator.
**

      }
      sqlite3ExprDelete(db, pDel);
      sqlite3VdbeResolveLabel(v, endLabel);
      break;
    }
#ifndef SQLITE_OMIT_TRIGGER
    case TK_RAISE: {
      assert( pExpr->affExpr==OE_Rollback 
           || pExpr->affExpr==OE_Abort
           || pExpr->affExpr==OE_Fail
           || pExpr->affExpr==OE_Ignore
      );
      if( !pParse->pTriggerTab ){
        sqlite3ErrorMsg(pParse,
                       "RAISE() may only be used within a trigger-program");
        return 0;
      }
      if( pExpr->affExpr==OE_Abort ){
        sqlite3MayAbort(pParse);
      }
      assert( !ExprHasProperty(pExpr, EP_IntValue) );
      if( pExpr->affExpr==OE_Ignore ){
        sqlite3VdbeAddOp4(
            v, OP_Halt, SQLITE_OK, OE_Ignore, 0, pExpr->u.zToken,0);
        VdbeCoverage(v);
      }else{
        sqlite3HaltConstraint(pParse, SQLITE_CONSTRAINT_TRIGGER,
                              pExpr->affExpr, pExpr->u.zToken, 0, 0);
      }

      break;
    }
#endif
  }
  sqlite3ReleaseTempReg(pParse, regFree1);

  sqlite3 *db = pParse->db;

  pExpr = sqlite3Expr(db, TK_REGISTER, 0);
  if( pExpr ){
    if( iCol>=0 && iCol!=pTab->iPKey ){
      pCol = &pTab->aCol[iCol];
      pExpr->iTable = regBase + iCol + 1;
      pExpr->affExpr = pCol->affinity;
      zColl = pCol->zColl;
      if( zColl==0 ) zColl = db->pDfltColl->zName;
      pExpr = sqlite3ExprAddCollateString(pParse, pExpr, zColl);
    }else{
      pExpr->iTable = regBase;
      pExpr->affExpr = SQLITE_AFF_INTEGER;
    }
  }
  return pExpr;
}

/*
** Return an Expr object that refers to column iCol of table pTab which

      Token tFrom;
      Expr *pRaise; 

      tFrom.z = zFrom;
      tFrom.n = nFrom;
      pRaise = sqlite3Expr(db, TK_RAISE, "FOREIGN KEY constraint failed");
      if( pRaise ){
        pRaise->affExpr = OE_Abort;
      }
      pSelect = sqlite3SelectNew(pParse, 
          sqlite3ExprListAppend(pParse, 0, pRaise),
          sqlite3SrcListAppend(pParse, 0, &tFrom, 0),
          pWhere,
          0, 0, 0, 0, 0
      );

  ** that created the expression.
  */
  static Expr *tokenExpr(Parse *pParse, int op, Token t){
    Expr *p = sqlite3DbMallocRawNN(pParse->db, sizeof(Expr)+t.n+1);
    if( p ){
      /* memset(p, 0, sizeof(Expr)); */
      p->op = (u8)op;
      p->affExpr = 0;
      p->flags = EP_Leaf;
      p->iAgg = -1;
      p->pLeft = p->pRight = 0;
      p->x.pList = 0;
      p->pAggInfo = 0;
      p->y.pTab = 0;
      p->op2 = 0;

trigger_cmd(A) ::= scanpt(B) select(X) scanpt(E).
   {A = sqlite3TriggerSelectStep(pParse->db, X, B, E); /*A-overwrites-X*/}

// The special RAISE expression that may occur in trigger programs
expr(A) ::= RAISE LP IGNORE RP.  {
  A = sqlite3PExpr(pParse, TK_RAISE, 0, 0); 
  if( A ){
    A->affExpr = OE_Ignore;
  }
}
expr(A) ::= RAISE LP raisetype(T) COMMA nm(Z) RP.  {
  A = sqlite3ExprAlloc(pParse->db, TK_RAISE, &Z, 1); 
  if( A ) {
    A->affExpr = (char)T;
  }
}
%endif  !SQLITE_OMIT_TRIGGER

%type raisetype {int}
raisetype(A) ::= ROLLBACK.  {A = OE_Rollback;}
raisetype(A) ::= ABORT.     {A = OE_Abort;}

              ExprSetProperty(pExpr, EP_Alias);
            }
          }else
#endif /* SQLITE_OMIT_UPSERT */
          {
#ifndef SQLITE_OMIT_TRIGGER
            if( iCol<0 ){
              pExpr->affExpr = SQLITE_AFF_INTEGER;
            }else if( pExpr->iTable==0 ){
              testcase( iCol==31 );
              testcase( iCol==32 );
              pParse->oldmask |= (iCol>=32 ? 0xffffffff : (((u32)1)<<iCol));
            }else{
              testcase( iCol==31 );
              testcase( iCol==32 );

     && pMatch
     && (pNC->ncFlags & NC_IdxExpr)==0
     && sqlite3IsRowid(zCol)
     && VisibleRowid(pMatch->pTab)
    ){
      cnt = 1;
      pExpr->iColumn = -1;
      pExpr->affExpr = SQLITE_AFF_INTEGER;
    }

    /*
    ** If the input is of the form Z (not Y.Z or X.Y.Z) then the name Z
    ** might refer to an result-set alias.  This happens, for example, when
    ** we are resolving names in the WHERE clause of the following command:
    **

** the child Expr objects in the Expr.pLeft and Expr.pRight subtrees
** are contained within the same memory allocation.  Note, however, that
** the subtrees in Expr.x.pList or Expr.x.pSelect are always separately
** allocated, regardless of whether or not EP_Reduced is set.
*/
struct Expr {
  u8 op;                 /* Operation performed by this node */
  char affExpr;          /* affinity, or RAISE type */
  u32 flags;             /* Various flags.  EP_* See below */
  union {
    char *zToken;          /* Token value. Zero terminated and dequoted */
    int iValue;            /* Non-negative integer value if EP_IntValue */
  } u;

  /* If the EP_TokenOnly flag is set in the Expr.flags mask, then no

  char zFlgs[60];
  pView = sqlite3TreeViewPush(pView, moreToFollow);
  if( pExpr==0 ){
    sqlite3TreeViewLine(pView, "nil");
    sqlite3TreeViewPop(pView);
    return;
  }
  if( pExpr->flags || pExpr->affExpr ){
    if( ExprHasProperty(pExpr, EP_FromJoin) ){
      sqlite3_snprintf(sizeof(zFlgs),zFlgs,"  fg.af=%x.%c iRJT=%d",
                       pExpr->flags, pExpr->affExpr ? pExpr->affExpr : 'n',
                       pExpr->iRightJoinTable);
    }else{
      sqlite3_snprintf(sizeof(zFlgs),zFlgs,"  fg.af=%x.%c",
                       pExpr->flags, pExpr->affExpr ? pExpr->affExpr : 'n');
    }
  }else{
    zFlgs[0] = 0;
  }
  switch( pExpr->op ){
    case TK_AGG_COLUMN: {
      sqlite3TreeViewLine(pView, "AGG{%d:%d}%s",

      sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
      sqlite3TreeViewExprList(pView, pExpr->x.pList, 0, 0);
      break;
    }
#ifndef SQLITE_OMIT_TRIGGER
    case TK_RAISE: {
      const char *zType = "unk";
      switch( pExpr->affExpr ){
        case OE_Rollback:   zType = "rollback";  break;
        case OE_Abort:      zType = "abort";     break;
        case OE_Fail:       zType = "fail";      break;
        case OE_Ignore:     zType = "ignore";    break;
      }
      sqlite3TreeViewLine(pView, "RAISE %s(%Q)", zType, pExpr->u.zToken);
      break;

  }
  if( zBinOp ){
    sqlite3TreeViewLine(pView, "%s%s", zBinOp, zFlgs);
    sqlite3TreeViewExpr(pView, pExpr->pLeft, 1);
    sqlite3TreeViewExpr(pView, pExpr->pRight, 0);
  }else if( zUniOp ){
    sqlite3TreeViewLine(pView, "%s%s", zUniOp, zFlgs);
   sqlite3TreeViewExpr(pView, pExpr->pLeft, 0);
  }
  sqlite3TreeViewPop(pView);
}


/*
** Generate a human-readable explanation of an expression list.