3 Cara Memeriksa Tipe Data Kolom di PostgreSQL

Berikut adalah tiga cara untuk mendapatkan tipe data kolom tertentu di MariaDB.

\d Perintah

Dalam psql, \d perintah menunjukkan informasi tentang tabel, tampilan, tampilan terwujud, indeks, urutan, atau tabel asing.

Kita dapat menggunakan perintah ini untuk memeriksa tipe data kolom dalam tabel yang diberikan:

\d public.actor

Hasil:

                                             Table "public.actor"
+-------------+-----------------------------+-----------+----------+-----------------------------------------+
|   Column    |            Type             | Collation | Nullable |                 Default                 |
+-------------+-----------------------------+-----------+----------+-----------------------------------------+
| actor_id    | integer                     |           | not null | nextval('actor_actor_id_seq'::regclass) |
| first_name  | character varying(45)       |           | not null |                                         |
| last_name   | character varying(45)       |           | not null |                                         |
| last_update | timestamp without time zone |           | not null | now()                                   |
+-------------+-----------------------------+-----------+----------+-----------------------------------------+
Indexes:
    "actor_pkey" PRIMARY KEY, btree (actor_id)
    "idx_actor_last_name" btree (last_name)
Referenced by:
    TABLE "film_actor" CONSTRAINT "film_actor_actor_id_fkey" FOREIGN KEY (actor_id) REFERENCES actor(actor_id) ON UPDATE CASCADE ON DELETE RESTRICT
Triggers:
    last_updated BEFORE UPDATE ON actor FOR EACH ROW EXECUTE FUNCTION last_updated()

Kita dapat menambahkan tanda plus (+ ) untuk mengungkapkan informasi tambahan:

\d+ public.actor

Hasil:

                                                                 Table "public.actor"
+-------------+-----------------------------+-----------+----------+-----------------------------------------+----------+--------------+-------------+
|   Column    |            Type             | Collation | Nullable |                 Default                 | Storage  | Stats target | Description |
+-------------+-----------------------------+-----------+----------+-----------------------------------------+----------+--------------+-------------+
| actor_id    | integer                     |           | not null | nextval('actor_actor_id_seq'::regclass) | plain    |              |             |
| first_name  | character varying(45)       |           | not null |                                         | extended |              |             |
| last_name   | character varying(45)       |           | not null |                                         | extended |              |             |
| last_update | timestamp without time zone |           | not null | now()                                   | plain    |              |             |
+-------------+-----------------------------+-----------+----------+-----------------------------------------+----------+--------------+-------------+
Indexes:
    "actor_pkey" PRIMARY KEY, btree (actor_id)
    "idx_actor_last_name" btree (last_name)
Referenced by:
    TABLE "film_actor" CONSTRAINT "film_actor_actor_id_fkey" FOREIGN KEY (actor_id) REFERENCES actor(actor_id) ON UPDATE CASCADE ON DELETE RESTRICT
Triggers:
    last_updated BEFORE UPDATE ON actor FOR EACH ROW EXECUTE FUNCTION last_updated()
Access method: heap

information_schema.columns Lihat

information_schema.columns tampilan berisi informasi tentang kolom:

SELECT
    column_name,
    data_type,
    character_maximum_length AS max_length,
    character_octet_length AS octet_length
FROM
    information_schema.columns
WHERE
    table_schema = 'public' AND 
    table_name = 'actor' AND
    column_name = 'first_name';

Hasil:

+-------------+-------------------+------------+--------------+
| column_name |     data_type     | max_length | octet_length |
+-------------+-------------------+------------+--------------+
| first_name  | character varying |         45 |          180 |
+-------------+-------------------+------------+--------------+

pg_typeof() Fungsi

pg_typeof() fungsi mengembalikan OID dari tipe data nilai yang diteruskan ke sana.

Oleh karena itu kita dapat menggunakannya untuk mendapatkan tipe data kolom dengan meneruskan kolom ke pg_typeof() fungsi saat menanyakan tabel:

SELECT pg_typeof(first_name)
FROM public.actor
LIMIT 1;

Hasil:

+-------------------+
|     pg_typeof     |
+-------------------+
| character varying |
+-------------------+

Di PostgreSQL, character varying adalah nama untuk varchar (sebenarnya, varchar adalah alias untuk character varying ).