Spark SQL 的 WHERE 子句

更新时间：2021-06-29 22:54:50 标签：sql spark where

提示

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Spark SQL 的 WHERE 子句用于根据指定的条件限制查询或子查询的 FROM 子句的结果。

语法

Spark SQL 的 WHERE 子句结构为：

WHERE boolean_expression

boolean_expression 是指定计算结果类型为布尔值的任何表达式。可以使用逻辑运算符（AND、OR）将两个或多个表达式组合在一起。

示例

以下是一些示例讲解：

-- 创建数据
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);

-- “WHERE” 子句中的比较运算符
SELECT * FROM person WHERE id > 200 ORDER BY id;
+---+----+---+
| id|name|age|
+---+----+---+
|300|Mike| 80|
|400| Dan| 50|
+---+----+---+

-- WHERE 子句中的比较运算符和逻辑运算符
SELECT * FROM person WHERE id = 200 OR id = 300 ORDER BY id;
+---+----+----+
| id|name| age|
+---+----+----+
|200|Mary|null|
|300|Mike|  80|
+---+----+----+

-- IS NULL 表达式：为空判断
SELECT * FROM person WHERE id > 300 OR age IS NULL ORDER BY id;
+---+----+----+
| id|name| age|
+---+----+----+
|200|Mary|null|
|400| Dan|  50|
+---+----+----+

-- 函数表达式
SELECT * FROM person WHERE length(name) > 3 ORDER BY id;
+---+----+----+
| id|name| age|
+---+----+----+
|100|John|  30|
|200|Mary|null|
|300|Mike|  80|
+---+----+----+

-- `BETWEEN` 表达式：在一个区间
SELECT * FROM person
WHERE id BETWEEN 200 AND 300
ORDER BY id;
+---+----+----+
| id|name| age|
+---+----+----+
|200|Mary|null|
|300|Mike|  80|
+---+----+----+

-- “WHERE”子句中的标量子查询
SELECT * FROM person
WHERE age > (SELECT avg(age) FROM person);
+---+----+---+
| id|name|age|
+---+----+---+
|300|Mike| 80|
+---+----+---+

-- “WHERE”子句中的相关子查询
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|
+---+----+----+

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