Mysql 如何在Rails 3+;博士后?
在我的模型中,我进行了以下自定义sql查询:Mysql 如何在Rails 3+;博士后?,mysql,ruby-on-rails-3,postgresql,boolean,coalesce,Mysql,Ruby On Rails 3,Postgresql,Boolean,Coalesce,在我的模型中,我进行了以下自定义sql查询: SELECT training_courses.id, training_courses.training_id, training_courses.course_id, training_courses.is_pre_test, training_courses.order_by, training_course_histories.id AS training_course_history_id,
SELECT
training_courses.id,
training_courses.training_id,
training_courses.course_id,
training_courses.is_pre_test,
training_courses.order_by,
training_course_histories.id AS training_course_history_id,
training_course_histories.finished_at,
training_course_histories.score,
CAST(coalesce(user_training_courses.id, 0) as BOOLEAN) as purchased
FROM
training_courses
LEFT OUTER JOIN training_course_histories
ON training_course_histories.training_course_id = training_courses.id AND training_course_histories.id = (
SELECT th1.id
FROM training_course_histories th1
WHERE th1.training_course_id = training_courses.id
AND th1.finished_at IS NOT NULL
AND th1.user_id = 1
ORDER BY th1.finished_at DESC LIMIT 1
)
LEFT OUTER JOIN user_training_courses
ON user_training_courses.training_course_id = training_courses.id AND user_training_courses.id = (
SELECT th2.id
FROM user_training_courses th2
WHERE th2.training_course_id = training_courses.id
AND th2.user_id = 1
)
WHERE (training_courses.training_id = 1)
GROUP BY
training_courses.id,
training_courses.id,
training_courses.training_id,
training_courses.course_id,
training_courses.is_pre_test,
training_courses.order_by,
training_course_histories.id,
training_course_histories.finished_at,
training_course_histories.score,
user_training_courses.id
ORDER BY
order_by ASC,
id ASC,
training_courses.order_by ASC,
training_courses.id ASC
以前,我使用的是Mysql数据库,所以,一点问题都没有,查询结果是:ISNULL(user\u training\u courses.id)as purchased
但现在,我正在使用Postgres,我必须购买CAST(coalesce(user\u training\u courses.id,0)作为布尔值
问题:对于Rails,purchased='t'或'f'(字符串)
我想要的:购买=真或假(布尔值)
可能吗
Thx.Rails PostgreSQL驱动程序理解PostgreSQL布尔值的形式是't'
和'f'
,并且通常正确地翻译它们。您的演员阵容:
CAST(coalesce(user_training_courses.id, 0) as BOOLEAN)
也可以:
psql=> select cast(11 as boolean), cast(1 as boolean), cast(0 as boolean);
bool | bool | bool
------+------+------
t | t | f
所以我猜Rails根本不知道你的演员阵容的类型。例如:
rails > ActiveRecord::Base.connection.select_rows('select cast(1 as boolean), 11 = 11')
=> [["t", "t"]]
您可以使用ActiveRecord::ConnectionAdapters::Column
中的设置常量将't'
和'f'
转换为布尔值:
TRUE_VALUES = [true, 1, '1', 't', 'T', 'true', 'TRUE'].to_set
FALSE_VALUES = [false, 0, '0', 'f', 'F', 'false', 'FALSE'].to_set
或者您可以使用:
但是,如果要使用低级SQL接口,您仍然需要知道所有列的类型,并手动进行排序。类似的问题也适用于整数、日期和任何其他返回的非字符串类型。最后,我的模型中有一个访问器来处理这种情况
def purchased
![false, 'false', 'f', 'FALSE', 'F', 0, '0'].include?(self[:purchased])
end
强制转换为布尔值根本不起作用…:-(谢谢,这是一个很好的解决方案。我知道其他类型也会有类似的问题…所以我选择了另一种方法将“f”和“t”转换为布尔值。您最好使用ActiveRecord::ConnectionAdapters::Column.value_to_boolean
。
def purchased
![false, 'false', 'f', 'FALSE', 'F', 0, '0'].include?(self[:purchased])
end