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Modifying Data: UPDATE
The UPDATE command allows you to update data already in the database:
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UPDATE table SET field1=val1, ..., fieldN=valN WHERE condition
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Tuples in table for which condition is true are updated.
Hence the WHERE clause controls which rows are affected by the UPDATE.
Example:
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> UPDATE weather
SET temp_hi = temp_hi - 2, temp_lo = temp_lo - 2
WHERE date > '1994-11-28';
new state of the data:
> SELECT * FROM weather;
city | temp_lo | temp_hi | prcp | date
---------------+---------+---------+------+------------
San Francisco | 46 | 50 | 0.25 | 1994-11-27
San Francisco | 41 | 55 | 0 | 1994-11-29
Hayward | 35 | 52 | | 1994-11-29
(3 rows)
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