Sottoquery in WHERE e SELECT
Unire i dati in SQL
Maham Faisal Khan
Senior Content Developer, DataCamp
Sintassi delle sottoquery in WHERE
- Tutti i semi join e anti join visti includevano una sottoquery in
WHERE WHEREè il posto più comune per le sottoquery
Sintassi per query con WHERE IN
SELECT *
FROM some_table
WHERE some_numeric_field IN (4, 8, 12);
Sintassi delle sottoquery in WHERE
SELECT *
FROM some_table
WHERE some_field IN
(inserisci qui la sottoquery);
Sintassi delle sottoquery in WHERE
SELECT *
FROM some_table
WHERE some_field IN
(SELECT some_numeric_field
FROM another_table
WHERE field2 = some_condition);
Sottoquery in SELECT
SELECT DISTINCT continent
FROM states;
|---------------|
| continent |
|---------------|
| Africa |
| Asia |
| Europe |
| North America |
| Oceania |
|---------------|
Sottoquery in SELECT
SELECT DISTINCT continent,(SELECT COUNT(*) FROM monarchsWHERE states.continent = monarch.continent) AS monarch_count FROM states;
| continent | monarch_count |
|---------------|-----------------|
| Africa | 0 |
| Asia | 2 |
| Europe | 2 |
| North America | 0 |
| Oceania | 0 |
Passiamo alla pratica !
Unire i dati in SQL
