Can anyone tell me which command is used for concatenate three columns data into one column in PostgreSQL database?
e.g.
If the columns are
begin | Month | Year
12 | 1 | 1988
13 | 3 | 1900
14 | 4 | 2000
15 | 5 | 2012
result like
Begin
12-1-1988
13-3-1900
14-4-2000
15-5-2012
Just use concatenation operator || : http://www.sqlfiddle.com/#!1/d66bb/2
select begin || '-' || month || '-' || year as begin
from t;
Output:
| BEGIN |
-------------
| 12-1-1988 |
| 13-3-1900 |
| 14-4-2000 |
| 15-5-2012 |
If you want to change the begin column itself, begin column must be of string type first, then do this: http://www.sqlfiddle.com/#!1/13210/2
update t set begin = begin || '-' || month || '-' || year ;
Output:
| BEGIN |
-------------
| 12-1-1988 |
| 13-3-1900 |
| 14-4-2000 |
| 15-5-2012 |
UPDATE
About this:
but m not getting null value column date
Use this:
select (begin || '-' || month || '-' || year)::date as begin
from t
Have a look at 9.4. String Functions and Operators
This is an old post, but I just stumbled upon it. Doesn't it make more sense to create a date data type? You can do that using:
select make_date(year, month, begin)
A date seems more useful than a string (and you can even format it however you like using to_char()).
