SQLiteDatabase.update 失败结果返回什么？

SQLiteDatabase 的插入、删除、更新、查找等默认返回值是什么啊？

比如下面的更新操作，失败的时候应该返回什么值？

/**
     * Convenience method for updating rows in the database.
     *
     * @param table the table to update in
     * @param values a map from column names to new column values. null is a
     *            valid value that will be translated to NULL.
     * @param whereClause the optional WHERE clause to apply when updating.
     *            Passing null will update all rows.
     * @param whereArgs You may include ?s in the where clause, which
     *            will be replaced by the values from whereArgs. The values
     *            will be bound as Strings.
     * @return the number of rows affected
     */
    public int update(String table, ContentValues values, String whereClause, String[] whereArgs) {
        return updateWithOnConflict(table, values, whereClause, whereArgs, CONFLICT_NONE);
    }

    /**
     * Convenience method for updating rows in the database.
     *
     * @param table the table to update in
     * @param values a map from column names to new column values. null is a
     *            valid value that will be translated to NULL.
     * @param whereClause the optional WHERE clause to apply when updating.
     *            Passing null will update all rows.
     * @param whereArgs You may include ?s in the where clause, which
     *            will be replaced by the values from whereArgs. The values
     *            will be bound as Strings.
     * @param conflictAlgorithm for update conflict resolver
     * @return the number of rows affected
     */
    public int updateWithOnConflict(String table, ContentValues values,
            String whereClause, String[] whereArgs, int conflictAlgorithm) {
        if (values == null || values.size() == 0) {
            throw new IllegalArgumentException("Empty values");
        }

        acquireReference();
        try {
            StringBuilder sql = new StringBuilder(120);
            sql.append("UPDATE ");
            sql.append(CONFLICT_VALUES[conflictAlgorithm]);
            sql.append(table);
            sql.append(" SET ");

            // move all bind args to one array
            int setValuesSize = values.size();
            int bindArgsSize = (whereArgs == null) ? setValuesSize : (setValuesSize + whereArgs.length);
            Object[] bindArgs = new Object[bindArgsSize];
            int i = 0;
            for (String colName : values.keySet()) {
                sql.append((i > 0) ? "," : "");
                sql.append(colName);
                bindArgs[i++] = values.get(colName);
                sql.append("=?");
            }
            if (whereArgs != null) {
                for (i = setValuesSize; i < bindArgsSize; i++) {
                    bindArgs[i] = whereArgs[i - setValuesSize];
                }
            }
            if (!TextUtils.isEmpty(whereClause)) {
                sql.append(" WHERE ");
                sql.append(whereClause);
            }

            SQLiteStatement statement = new SQLiteStatement(this, sql.toString(), bindArgs);
            try {
                return statement.executeUpdateDelete();
            } finally {
                statement.close();
            }
        } finally {
            releaseReference();
        }
    }

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失败的话，得看你什么何种原因吧，如果是sql写错了就直接抛出异常了。如果要更新的数据不存在肯定是返回0了啊，