Question

有H2表：

CREATE TABLE IF NOT EXISTS sometable (ondate DATE NOT NULL);

使用数据

INSERT INTO sometable VALUES ('2015-07-07');
INSERT INTO sometable VALUES ('2014-07-07');
INSERT INTO sometable VALUES ('2013-07-07');

我想限制所选的数据量，但以下选择不起作用。为什么呢？

SELECT YEAR(CONVERT(ondate, TIMESTAMP)) AS yr FROM sometable WHERE yr = 2015

错误消息是SELECT YEAR（CONVERT（ondate，TIMESTAMP））AS yr FROM sometable WHERE yr = 2015;专栏＆＃34; YR＆＃34;未找到; SQL语句：SELECT YEAR（CONVERT（ondate，TIMESTAMP））AS yr FROM sometable WHERE yr = 2015 [42122-176] 42S22 / 42122

Answer 1

这不是特定于H2的，这将在许多RDBMS上发生。 yr列实际上不是SELECT子句的一部分，它是CONVERT语句。如果要这样做，请将整个语句包装在派生表中并查询，或者使用与WHERE中的SELECT相同的子句。

例如;

SELECT * FROM (SELECT YEAR(CONVERT(ondate, TIMESTAMP)) AS yr 
FROM sometable) a WHERE a.yr = 2015

OR

SELECT YEAR(CONVERT(ondate, TIMESTAMP)) AS yr FROM sometable 
WHERE YEAR(CONVERT(ondate, TIMESTAMP)) = 2015

Answer 2

您不能在where子句中引用列别名。

SELECT
YEAR(CONVERT(ondate, TIMESTAMP)) AS yr
FROM sometable
WHERE YEAR(CONVERT(ondate, TIMESTAMP)) = 2015

Answer 3

错误表明未找到列yr，因为yr不是您的列名，它只是一个别名。 SQL不能将别名视为可以这样写的列名

SELECT 
    YEAR(CONVERT(ondate, TIMESTAMP)) AS yr 
FROM sometable WHERE 
    YEAR(CONVERT(ondate, TIMESTAMP)) = 2015

H2选择表达式列别名

3 个答案: