WHERE

描述

根据指定的条件限制查询或子查询的 FROM 子句的结果。

语法

WHERE boolean_expression

参数

• boolean_expression

  计算得出 BOOLEAN 结果类型的任何表达式。 可以使用逻辑运算符（例如 AND 或 OR）组合两个或更多个表达式。

示例

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;

+---------+-----------+----------+
|       salary|       name|       age|
+---------+-----------+----------+
|      200|       Mary|      NULL|
+---------+-----------+----------+
|      300|       Mike|        80|
+---------+-----------+----------+

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