WHERE 句
説明
WHERE 句は、クエリまたはサブクエリの FROM 句の結果を、指定された条件に基づいて制限するために使用されます。
構文
WHERE boolean_expression
パラメータ
-
boolean_expression
結果の型が
booleanに評価される任意の式を指定します。2つ以上の式は、論理演算子（AND、OR）を使用して組み合わせることができます。
例
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;
+---+----+---+
| id|name|age|
+---+----+---+
|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;
+---+----+----+
| id|name| age|
+---+----+----+
|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;
+---+----+----+
| id|name| age|
+---+----+----+
|200|Mary|null|
|400| Dan| 50|
+---+----+----+
-- Function expression in `WHERE` clause.
SELECT * FROM person WHERE length(name) > 3 ORDER BY id;
+---+----+----+
| id|name| age|
+---+----+----+
|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;
+---+----+----+
| id|name| age|
+---+----+----+
|200|Mary|null|
|300|Mike| 80|
+---+----+----+
-- Scalar Subquery in `WHERE` clause.
SELECT * FROM person WHERE age > (SELECT avg(age) FROM person);
+---+----+---+
| id|name|age|
+---+----+---+
|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
);
+---+----+----+
|id |name|age |
+---+----+----+
|200|Mary|null|
+---+----+----+