Vind de juiste tabel

SQL toepassen op problemen uit de praktijk

Dmitriy (Dima) Gorenshteyn

Lead Data Scientist, Memorial Sloan Kettering Cancer Center

Overwhelmed man staring at busy blackboard

Welke tabel gebruik je?

Welke kolommen staan in je tabellen?
Wat staat er in die kolommen?

SELECT * 
FROM payment;

Beperk je resultaten met LIMIT

SELECT * 
FROM payment;

rental_id rental_date       inventory_id customer_id return_date
2         2005-05-24 22:54:33    1525    459         2005-05-28 19:40:33
3         2005-05-24 23:03:39    1711    408         2005-06-01 22:12:39
4         2005-05-24 23:04:41    2452    333         2005-06-03 01:43:41
5         2005-05-24 23:05:21    2079    222         2005-06-02 04:33:21
6         2005-05-24 23:08:07    2792    549         2005-05-27 01:32:07
7         2005-05-24 23:11:53    3995    269         2005-05-29 20:34:53
8         2005-05-24 23:31:46    2346    239         2005-05-27 23:33:46
...................16035 MORE ROWS......................................

Beperk je resultaten met LIMIT

SELECT * 
FROM payment
LIMIT 5;

rental_id rental_date       inventory_id customer_id return_date
2         2005-05-24 22:54:33    1525    459         2005-05-28 19:40:33
3         2005-05-24 23:03:39    1711    408         2005-06-01 22:12:39
4         2005-05-24 23:04:41    2452    333         2005-06-03 01:43:41
5         2005-05-24 23:05:21    2079    222         2005-06-02 04:33:21

Welke tabellen staan in mijn database?

PostgreSQL:

SELECT * 
FROM pg_catalog.pg_tables
;

schemaname     tablename     tableowner 
public         address       postgres
public         actor         postgres
public         film_actor    postgres
public         language      postgres 
...            ...           ...

Welke tabellen staan in mijn database?

PostgreSQL:

SELECT * 
FROM pg_catalog.pg_tables
WHERE schema_name = 'public;

schemaname     tablename     tableowner 
public         address       postgres
public         actor         postgres
public         film_actor    postgres
public         language      postgres
...            ...           ...

Welke tabellen staan in mijn database?

PostgreSQL:

SELECT * FROM pg_catalog.pg_tables;

SQL Server - TSQL:

SELECT * FROM INFORMATION_SCHEMA.TABLES;

MySQL:

SHOW TABLES;

...

Vind de tabellen die je nodig hebt

SQL toepassen op problemen uit de praktijk