从select语句的另一列向mysql中添加新列

Question

I have a datetime() column date_time in my database.

I need to convert this to date() and create a new temporary column date_field till the session ends.

I've tried this:

$query1 = SELECT date_time, date(date_time) as date_field FROM table_name....

This works and creates a temp column date_field with all the date values for the date_time field

Problem : This only works for this query. I also have another query which searches for date_time field and thus results into a DB error Unknown field 'date_field'.

$query2 = SELECT date_field FROM table_name
                                    | This table doesn't have date_field as a column

Can this field be created so that I can use this for a time till the session ends ? as we do for temporary tables ?

Note: I can't use ALTER to add new column here due to code limitations.

Any ideas ?

Thanks!

Answer 1

In the first query, you dont really create any column, you just return a a column (date_time), run some function on it (date()) and give it an alias name (date_field). This happens only in the result set, and abvioysly cant be used outside of this query.

What you need to do is simply use the same in the second query: instead of select date field you need select date(date_time) as date_field