> ## Documentation Index
> Fetch the complete documentation index at: https://docs.baenninger.me/llms.txt
> Use this file to discover all available pages before exploring further.

# Subqueries

Unterabfragen sind einfach gesagt verschachtelte Queries. Bei Subqueries gibt es keine Syntax, wie beispielsweise bei Joins, aber es gibt gewisse Regeln, welche in den Beispielen visualisiert werden.

## Beispiele

```sql theme={null}
SELECT Name FROM Cities
WHERE Id IN (
    SELECT CityId FROM Customers
    WHERE FirstName LIKE 'F%'
);
```

```sql theme={null}
SELECT AVG(NumOfIngredients) FROM (
    SELECT COUNT(*) AS NumOfIngredients FROM PizzaIngredients
    GROUP BY PizzaId
) T;
```

```sql theme={null}
SELECT Street, City.ZipCode, City.Name FROM Customers
JOIN City ON Customers.CityId = City.Id
WHERE Customers.Id IN (
    SELECT CustomerId FROM Orders
    WHERE Id = 3
);
```

```sql theme={null}
SELECT Name FROM Ingredients
WHERE Id IN (
    SELECT IngredientId FROM PizzaIngredients
    WHERE PizzaId IN (
        SELECT Id FROM Pizzas
        WHERE Price = (
            SELECT MAX(Price) FROM Pizzas
        )
    )
);
```

```sql theme={null}
SELECT Name FROM Ingredients
WHERE Id IN (
    SELECT IngredientId
    FROM (SELECT IngredientId, COUNT(*) as Count
          FROM PizzaIngredients GROUP BY IngredientId) T
    WHERE Count = (
        SELECT MAX(Count)
        FROM (SELECT IngredientId, COUNT(*) as Count
              FROM PizzaIngredients GROUP BY IngredientId) TT
    )
);
```