sql - 在 varchar 列中进行数字比较

Question

我需要在 PostgreSQL 数据库上编写 HQL 查询(如果可能的话不是原生 SQL)，选择 attr 值大于 39 的行。问题是 attr column 是一个 varchar 列，不仅包含数字。我只需要数字并且只需要大于 39。适合我的 native 查询如下:

SELECT * FROM my_table WHERE attr ~ '^[0-9\.]+$' AND CAST(attr AS BIGINT) > 39;

我尝试了以下 HQL 等效项(均无效):

1. SELECT myTable FROM MyTable myTable WHERE attr ~ '^[0-9\.]+$' AND CAST(attr AS long) > 39; //~ cannot be used in HQL query
2. SELECT myTable FROM MyTable myTable WHERE ISNUMERIC(attr) = 1 AND CAST(attr AS long) > 39; //cannot extract result set
3. SELECT myTable FROM MyTable myTable WHERE attr LIKE '^[0-9\.]+$' AND CAST(attr AS long) > 39; //cannot extract result set
4. SELECT myTable FROM MyTable myTable WHERE CAST(attr AS long) > 39; //cannot extract result set
5. SELECT myTable FROM MyTable myTable WHERE attr > '39'; //wrong data types - rows with 4 in the attr column are found

Answer 1

尝试创建一个像这样的 PostgreSQL 函数:

CREATE FUNCTION parse_attr_to_boolean(attr character varying) RETURNS BOOLEAN AS $$
        BEGIN
                RETURN attr ~ '^[0-9\.]+$' AND CAST(attr AS BIGINT) > 39;
        END;
$$ LANGUAGE plpgsql;

现在，您只需在 HQL 查询中调用函数即可:

SELECT t 
FROM MyTable t 
WHERE parse_attr_to_boolean(t.attr)

只需要注册SQL函数，如parse_attr_to_boolean , 如果在 SELECT 子句中使用该函数。但是，由于您在 WHERE 子句中使用它，因此它可以按原样传递给 SQL 查询。