Обсуждение: Help On Postgresql

Jaydip wrote:

> Dear Friends
> 
> I am Jaydip Dewanji working as a Sr. Programmer for Ontrack Systems Ltd.
> 
> I have some questions regarding Postgresql which are listed below:
> 
> a) How do I retrieve the Year,Month,Day,Hr,Minute or Second value from a Da=
> te/DateTime variable.
> 
>     For Example : i> In Oracle to_char(dt,'yyyy') - for extracting the year=
>  value from a date variable dt
>                          ii> In SqlServer datepart(hh,dt) - for extracting =
> the Hour value from a date variable dt I don't know what variables you are talking about. Which interface do
yo use ? My client programs recieve plain text from postgres, so there are no
variables. 
> b) Can I create an identity column in Postgresql the value of which column =
> will start from 1 say and keep
>     on incrementing by 1 OR how can I serve my purpose in any other way.
 Use the data type SERIAL. If you say e.g.
 CREATE TABLE mytable ( key SERIAL, .... );
 Then every time you insert a new row key will increment automatically.

Arne.

----- Original Message -----

From: Jaydip

To: pgsql-sql@postgresql.org

Sent: Thursday, August 23, 2001 2:50 AM

Subject: Help On Postgresql

Dear Friends

 

I am Jaydip Dewanji working as a Sr. Programmer for Ontrack Systems Ltd.

 

I have some questions regarding Postgresql which are listed below:

 

a) How do I retrieve the Year,Month,Day,Hr,Minute or Second value from a Date/DateTime variable.

 

    For Example : i> In Oracle to_char(dt,'yyyy') - for extracting the year value from a date variable dt

                         ii> In SqlServer datepart(hh,dt) - for extracting the Hour value from a date variable dt

 

b) Can I create an identity column in Postgresql the value of which column will start from 1 say and keep

    on incrementing by 1 OR how can I serve my purpose in any other way.

 

 

Please do let me know if any one of you have any solution.

 

Regards

 

Jaydip

On Thu, 23 Aug 2001, Jaydip wrote:

> a) How do I retrieve the Year,Month,Day,Hr,Minute or Second value from a Date/DateTime variable.
> 
>     For Example : i> In Oracle to_char(dt,'yyyy') - for extracting the year value from a date variable dt
>                  ii> In SqlServer datepart(hh,dt) - for extracting the Hour value from a date variable dt

I'm not sure what versions all of these came in at, but:There is a to_char which should be somewhat compatible with
oracle's,aswell as a datepart (whose part names are like 'year', 'month', ...)and extract(<part> from dt)
 

> b) Can I create an identity column in Postgresql the value of which column will start from 1 say and keep
>     on incrementing by 1 OR how can I serve my purpose in any other way.

Look at sequences and the serial pseudo-type.

a) Either of these should return the yaer (2001). See section 4.7 of the
user guide
SELECT EXTRACT(YEAR FROM TIMESTAMP '2001-02-16 20:38:40'); 
SELECT date_part('year', TIMESTAMP '2001-02-16 20:38:40');
b) The serial datatype will do this. It is actually just an int4 with a
default value of nextval('<sequence name>').
- Stuart


> -----Original Message-----
> From:    Jaydip [SMTP:jaydip@ontrackindia.com]
> Sent:    Thursday, August 23, 2001 8:51 AM
> To:    pgsql-sql@postgresql.org
> Subject:    Help On Postgresql
> 
> Dear Friends
>  
> I am Jaydip Dewanji working as a Sr. Programmer for Ontrack Systems Ltd.
>  
> I have some questions regarding Postgresql which are listed below:
>  
> a) How do I retrieve the Year,Month,Day,Hr,Minute or Second value from a
> Date/DateTime variable.
>  
>     For Example : i> In Oracle to_char(dt,'yyyy') - for extracting the
> year value from a date variable dt
>                          ii> In SqlServer datepart(hh,dt) - for extracting
> the Hour value from a date variable dt
>  
> b) Can I create an identity column in Postgresql the value of which column
> will start from 1 say and keep
>     on incrementing by 1 OR how can I serve my purpose in any other way.
>  
>  
> Please do let me know if any one of you have any solution.
>  
> Regards
>  
> Jaydip