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mysql> UPDATE stockData SET symbol = 'AAPL' WHERE symbol IS NULL;
Query OK, 5933 rows affected (0.21 sec)
Rows matched: 5933  Changed: 5933  Warnings: 0

mysql> SELECT * FROM stockData LIMIT 10;+------------+--------+--------+--------+--------+--------+----------+----------+
| date       | symbol | open   | high   | low    | close  | volume   | adjClose |
+------------+--------+--------+--------+--------+--------+----------+----------+
| 2008-03-14 | AAPL   | 129.88 |  130.3 |  124.2 | 126.61 | 41308600 |   126.61 | 
| 2008-03-13 | AAPL   |  124.1 |  129.5 |    123 | 127.94 | 45075100 |   127.94 | 
| 2008-03-12 | AAPL   | 127.04 | 128.68 | 125.17 | 126.03 | 37825200 |   126.03 | 
| 2008-03-11 | AAPL   |  124.1 | 127.48 |    122 | 127.35 | 41569400 |   127.35 | 
| 2008-03-10 | AAPL   | 121.98 | 123.46 | 119.37 | 119.69 | 35699600 |   119.69 | 
| 2008-03-07 | AAPL   | 120.41 | 122.98 | 119.05 | 122.25 | 43945100 |   122.25 | 
| 2008-03-06 | AAPL   | 124.61 |  127.5 | 120.81 | 120.93 | 52603500 |   120.93 | 
| 2008-03-05 | AAPL   | 123.58 | 125.14 | 122.25 | 124.49 | 43510300 |   124.49 | 
| 2008-03-04 | AAPL   | 121.99 | 124.88 |  120.4 | 124.62 | 63747100 |   124.62 | 
| 2008-03-03 | AAPL   | 124.44 | 125.98 |    118 | 121.73 | 56894400 |   121.73 | 
+------------+--------+--------+--------+--------+--------+----------+----------+
10 rows in set (0.00 sec)

mysql> quit