WHERE-Klausel
Gilt für: Databricks SQL Databricks Runtime
Schränkt die Ergebnisse der FROM
-Klausel einer Abfrage oder einer Unterabfrage abhängig von der angegebenen Bedingung ein.
Syntax
WHERE boolean_expression
Parameter
-
Beliebiger Ausdruck, dessen Auswertung den Ergebnistyp
BOOLEAN
ergibt. Sie können zwei oder mehr Ausdrücke mithilfe von logischen Operatoren (z. B.AND
oderOR
) kombinieren.
Beispiele
> CREATE TABLE person (id INT, name STRING, age INT);
> INSERT INTO person VALUES
(100, 'John', 30),
(200, 'Mary', NULL),
(300, 'Mike', 80),
(400, 'Dan' , 50);
-- Comparison operator in `WHERE` clause.
> SELECT * FROM person WHERE id > 200 ORDER BY id;
300 Mike 80
400 Dan 50
-- Comparison and logical operators in `WHERE` clause.
> SELECT * FROM person WHERE id = 200 OR id = 300 ORDER BY id;
200 Mary NULL
300 Mike 80
-- IS NULL expression in `WHERE` clause.
> SELECT * FROM person WHERE id > 300 OR age IS NULL ORDER BY id;
200 Mary null
400 Dan 50
-- Function expression in `WHERE` clause.
> SELECT * FROM person WHERE length(name) > 3 ORDER BY id;
100 John 30
200 Mary NULL
300 Mike 80
-- `BETWEEN` expression in `WHERE` clause.
SELECT * FROM person WHERE id BETWEEN 200 AND 300 ORDER BY id;
200 Mary NULL
300 Mike 80
-- Scalar Subquery in `WHERE` clause.
> SELECT * FROM person WHERE age > (SELECT avg(age) FROM person);
300 Mike 80
-- Correlated Subquery in `WHERE` clause.
> SELECT * FROM person AS parent
WHERE EXISTS (SELECT 1 FROM person AS child
WHERE parent.id = child.id
AND child.age IS NULL);
200 Mary NULL