Question

UPDATE

+-----+------------------+-------------+
| id  | datenum          | F1_baro_20_ |
+-----+------------------+-------------+
|   1 | 734152.000000000 |     1005.21 |
|   2 | 734152.006944445 |     1005.26 |
+-----+------------------+-------------+

this is my table

And this is my new table

+-----+------------------+-------------+------------+
| id  | datenum          | F1_baro_20_ |new column  |
+-----+------------------+-------------+------------+
|   1 | 734152.000000000 |     1005.21 |            |
|   2 | 734152.006944445 |     1005.26 |            |
+-----+------------------+-------------+------------+

I want to insert data to the ‘new_colum’ where old_datenum=new_datenum but I don’t wan to modify the existing data!

Answer 1

Try this.

Add a new column with the following SQL query:

ALTER TABLE myTable ADD newColumn <datatype>

Where <datatype> can be something like int, text, longtext, varchar(50) – depending on what you need.

Then update only this column with SQL queries like this:

UPDATE TABLE myTable SET newColumn = 'Hello this is my data'

or if you need to update a specific row (chosen where the column id is 2):

UPDATE TABLE myTable SET newColumn = 'Hello this is my data' WHERE id = '2'

---

Here’s the simple SQL query to copy the data from datenum to newColumn:

UPDATE myTable SET newColumn = datenum

Run that code once (but with your table name and column name of course) and you’ll see that the data is copied.

---

Or if you want to do it with, for example, PHP:

$rs = mysql_query('SELECT * FROM myTable ORDER BY id ASC');
while ($row = mysql_fetch_array($rs)) {
  $id = $row['id'];
  $new_datenum = $row['datenum'];
  $q = mysql_query('UPDATE myTable SET newColumn = $new_datenum WHERE id = $id');
}

This will also copy all the data from datenum to newColumn.