HAVING-KlauselHAVING clause

Die- HAVING Klausel wird verwendet, um die Ergebnisse zu filtern, die von GROUP BY basierend auf der angegebenen Bedingung erzeugt werden.The HAVING clause is used to filter the results produced by GROUP BY based on the specified condition. Sie wird häufig in Verbindung mit einer Group by -Klausel verwendet.It is often used in conjunction with a GROUP BY clause.

SyntaxSyntax

HAVING boolean_expression

ParameterParameters

  • boolean_expressionboolean_expression

    Gibt jeden Ausdruck an, der zu einem Ergebnistyp ausgewertet wird boolean .Specifies any expression that evaluates to a result type boolean. Zwei oder mehr Ausdrücke können mithilfe der logischen Operatoren ( AND ,) kombiniert werden OR .Two or more expressions may be combined together using the logical operators ( AND, OR ).

    HinweisNote

    Die in der-Klausel angegebenen Ausdrücke HAVING können nur auf Folgendes verweisen:The expressions specified in the HAVING clause can only refer to:

    1. KonstantenConstants
    2. Ausdrücke, die in Group by angezeigt werdenExpressions that appear in GROUP BY
    3. AggregatfunktionenAggregate functions

BeispieleExamples

CREATE TABLE dealer (id INT, city STRING, car_model STRING, quantity INT);
INSERT INTO dealer VALUES
    (100, 'Fremont', 'Honda Civic', 10),
    (100, 'Fremont', 'Honda Accord', 15),
    (100, 'Fremont', 'Honda CRV', 7),
    (200, 'Dublin', 'Honda Civic', 20),
    (200, 'Dublin', 'Honda Accord', 10),
    (200, 'Dublin', 'Honda CRV', 3),
    (300, 'San Jose', 'Honda Civic', 5),
    (300, 'San Jose', 'Honda Accord', 8);

-- `HAVING` clause referring to column in `GROUP BY`.
SELECT city, sum(quantity) AS sum FROM dealer GROUP BY city HAVING city = 'Fremont';
+-------+---+
|   city|sum|
+-------+---+
|Fremont| 32|
+-------+---+

-- `HAVING` clause referring to aggregate function.
SELECT city, sum(quantity) AS sum FROM dealer GROUP BY city HAVING sum(quantity) > 15;
+-------+---+
|   city|sum|
+-------+---+
| Dublin| 33|
|Fremont| 32|
+-------+---+

-- `HAVING` clause referring to aggregate function by its alias.
SELECT city, sum(quantity) AS sum FROM dealer GROUP BY city HAVING sum > 15;
+-------+---+
|   city|sum|
+-------+---+
| Dublin| 33|
|Fremont| 32|
+-------+---+

-- `HAVING` clause referring to a different aggregate function than what is present in
-- `SELECT` list.
SELECT city, sum(quantity) AS sum FROM dealer GROUP BY city HAVING max(quantity) > 15;
+------+---+
|  city|sum|
+------+---+
|Dublin| 33|
+------+---+

-- `HAVING` clause referring to constant expression.
SELECT city, sum(quantity) AS sum FROM dealer GROUP BY city HAVING 1 > 0 ORDER BY city;
+--------+---+
|    city|sum|
+--------+---+
|  Dublin| 33|
| Fremont| 32|
|San Jose| 13|
+--------+---+

-- `HAVING` clause without a `GROUP BY` clause.
SELECT sum(quantity) AS sum FROM dealer HAVING sum(quantity) > 10;
+---+
|sum|
+---+
| 78|
+---+