postgresql
Postgres Tip and Tricks

Alternativa al DATEADD in Postgres

• SELECT CURRENT_DATE + '1 day'::INTERVAL
• SELECT '1999-12-11'::TIMESTAMP + '19 days'::INTERVAL
• SELECT '1 month'::INTERVAL + '1 month 3 days'::INTERVAL

Valori separati da virgola di una colonna

SELECT 
    string_agg(<TABLE_NAME>.<COLUMN_NAME>, ',') 
FROM 
    <SCHEMA_NAME>.<TABLE_NAME> T

Elimina i record duplicati dalla tabella Postgres

DELETE 
    FROM <SCHEMA_NAME>.<Table_NAME> 
WHERE 
    ctid NOT IN
        (
        SELECT 
            MAX(ctid) 
        FROM 
            <SCHEMA_NAME>.<TABLE_NAME> 
        GROUP BY 
            <SCHEMA_NAME>.<TABLE_NAME>.*
        )
;

Aggiorna query con join tra due tabelle alternative poiché Postresql non supporta join nella query di aggiornamento.

    update <SCHEMA_NAME>.<TABLE_NAME_1> AS A
    SET <COLUMN_1> = True       
    FROM <SCHEMA_NAME>.<TABLE_NAME_2> AS B 
    WHERE 
        A.<COLUMN_2> = B.<COLUMN_2> AND
        A.<COLUMN_3> = B.<COLUMN_3>

Differenza tra due date timestamp mese saggio e anno saggio

Differenza mensile tra due date (timestamp)

select 
    (
        (DATE_PART('year', AgeonDate) - DATE_PART('year', tmpdate)) * 12 
        +
        (DATE_PART('month', AgeonDate) - DATE_PART('month', tmpdate))
    ) 
from dbo."Table1"

Differenza annuale tra due date (timestamp)

select (DATE_PART('year', AgeonDate) - DATE_PART('year', tmpdate)) from dbo."Table1"

Query su Copia / Sposta / Trasferisci i dati della tabella da un database ad un'altra tabella di database con lo stesso schema

Primo Esegui

CREATE EXTENSION DBLINK;

Poi

INSERT INTO 
    <SCHEMA_NAME>.<TABLE_NAME_1> 
SELECT * 
FROM 
    DBLINK(
    'HOST=<IP-ADDRESS> USER=<USERNAME> PASSWORD=<PASSWORD> DBNAME=<DATABASE>',
    'SELECT * FROM <SCHEMA_NAME>.<TABLE_NAME_2>')
    AS <TABLE_NAME>
    (
    <COLUMN_1> <DATATYPE_1>, 
    <COLUMN_1> <DATATYPE_2>, 
    <COLUMN_1> <DATATYPE_3>
    );