+---------------------------+---------+----------------+---------------------+--------------------+----------+----------------------+------------------+--------+
|           Date            | Account |      ISIN      |      Quantity       |       Value        | Currency | Price                | PriceCHF         | FXRate |
+---------------------------+---------+----------------+---------------------+--------------------+----------+----------------------+------------------+--------+
| 2019-02-28 00:00:00       |       1 | CH5055181629   | 0.00000000          | 0.000000           | CHF      | 1124.56              | 1124.56          | 1      |
| 2019-02-28 00:00:00       |       6 | CH5055181629   | 0.37866100          | 425.827014         | CHF      | 1124.56              | 1124.56          | 1      |
| 2019-02-28 00:00:00       |       7 | CH5055181629   | 0.67151800          | 755.162282         | CHF      | 1124.56              | 1124.56          | 1      |
| 2019-02-28 00:00:00       |       8 | CH5055181629   | 0.45240000          | 508.750944         | CHF      | 1124.56              | 749.7067         | 1.5    |
| 2019-02-28 00:00:00       |       9 | CH5055181622   | 0.02204500          | 24.790925          | CHF      | 1124.56              | 749.7067         | 1.5    |
| 2019-02-28 00:00:00       |      10 | CH5055181622   | 0.08353300          | 93.937870          | CHF      | 1124.56              | 749.7067         | 1.5    |
| 2019-02-28 00:00:00       |      11 | CH5055181622   | 0.89667100          | 1008.360340        | CHF      | 1124.56              | 749.7067         | 1.5    |
+---------------------------+---------+----------------+---------------------+--------------------+----------+----------------------+------------------+--------+

SELECT *
INTO   #assets
FROM   (SELECT xxx
        FROM   yyyy) a

DECLARE @cols  AS NVARCHAR(max),
        @query AS NVARCHAR(max);

SET @cols = Stuff((SELECT DISTINCT ',' + Quotename(c.ISIN)
                   FROM   #assets c
                   FOR xml path(''), type).value('.', 'NVARCHAR(MAX)'), 1, 1, ''
            )
SET @query = 'SELECT date, account, ' + @cols
             + ' from #assets x pivot ( max(quantity) for ISIN in (' + @cols
             + ')) p '

EXECUTE(@query)

DROP TABLE #assets

+---------------------------+---------+--------------+----------------+
|           Date            | Account | CH5055181629 | CH5055181622   |
+---------------------------+---------+--------------+----------------+
| 2019-02-28 00:00:00       |       1 | 0.000000     | NULL           |
| 2019-02-28 00:00:00       |       6 | 0.378661     | NULL           |
| 2019-02-28 00:00:00       |       7 | 0.671518     | NULL           |
| 2019-02-28 00:00:00       |       8 | 0.452400     | NULL           |
| 2019-02-28 00:00:00       |       9 | 0.000000     | NULL           |
| 2019-02-28 00:00:00       |      10 | 0.000000     | NULL           |
| 2019-02-28 00:00:00       |      11 | 0.000000     | NULL           |
| 2019-02-28 00:00:00       |       1 | NULL         | 0.000000       |
| 2019-02-28 00:00:00       |       6 | NULL         | 0.000000       |
| 2019-02-28 00:00:00       |       7 | NULL         | 0.000000       |
| 2019-02-28 00:00:00       |       8 | NULL         | 0.000000       |
| 2019-02-28 00:00:00       |       9 | NULL         | 0.022045       |
| 2019-02-28 00:00:00       |      10 | NULL         | 0.083533       |
| 2019-02-28 00:00:00       |      11 | NULL         | 0.896671       |
+---------------------------+---------+--------------+----------------+

+---------------------------+---------+-----------------------+-----------------------+--------------------+--------------------+
|           Date            | Account | CH5055181629_quantity | CH5055181622_quantity | CH5055181629_value | CH5055181622_value |
+---------------------------+---------+-----------------------+-----------------------+--------------------+--------------------+
| 2019-02-28 00:00:00       |       1 | 0.000000              | 0.000000              | 0.000000           | 0.000000           |
| 2019-02-28 00:00:00       |       6 | 0.378661              | 0.000000              | 425.827014         | 0.000000           |
| 2019-02-28 00:00:00       |       7 | 0.671518              | 0.000000              | 755.162282         | 0.000000           |
| 2019-02-28 00:00:00       |       8 | 0.452400              | 0.000000              | 508.750944         | 0.000000           |
| 2019-02-28 00:00:00       |       9 | 0.000000              | 0.022045              | 0.000000           | 24.790925          |
| 2019-02-28 00:00:00       |      10 | 0.000000              | 0.083533              | 0.000000           | 93.937870          |
| 2019-02-28 00:00:00       |      11 | 0.000000              | 0.896671              | 0.000000           | 1'008.360340       |
+---------------------------+---------+-----------------------+-----------------------+--------------------+--------------------+