SQL
Updates
You can update existing rows using the `UPDATE` command. Suppose you discover the temperature readings are all off by 2 degrees after November 28. You can correct the data as follows:  
```sql
UPDATE weather
SET temp_hi = temp_hi - 2,  temp_lo = temp_lo - 2
WHERE date > '1994-11-28';
```  
Look at the new state of the data:  
```sql
SELECT *
FROM weather;
```  
|     city      | temp_lo | temp_hi | prcp |    date    |
|---------------|--------:|--------:|-----:|------------|
| San Francisco | 46      | 50      | 0.25 | 1994-11-27 |
| San Francisco | 41      | 55      | 0.0  | 1994-11-29 |
| Hayward       | 35      | 52      | NULL | 1994-11-29 |