续集宝石增量 [英] Sequel gem increment
问题描述
我正在尝试使用Ruby Sequel gem进行数据库操作.
I am trying to use the Ruby Sequel gem for DB operations.
我对增加和减少值感到困惑.
I am stuck for incrementing and decrementing values.
医生说这应该可行,尽管对我来说能够加一个数字和一个符号似乎很奇怪.
The doc says that this should work, even though it seems very strange for me to be able to add a number and a symbol.
2.0.0-p247 :019 > require 'sequel'
=> true
2.0.0-p247 :020 > s = Sequel.connect('sqlite://db.sqlite')
=> #<Sequel::SQLite::Database: "sqlite://db.sqlite">
2.0.0-p247 :021 > s[:query_volume].update_sql(:queries => 3)
=> "UPDATE `query_volume` SET `queries` = 3"
2.0.0-p247 :022 > s[:query_volume].update_sql(:queries => :queries + 3)
NoMethodError: undefined method `+' for :queries:Symbol
from (irb):21
from /Users/avandra/.rvm/rubies/ruby-2.0.0-p247/bin/irb:16:in `<main>'
但是如您所见,它在查询符号上提供了未定义的方法.有点同意为什么对我来说很奇怪.
But as you can see it gives undefined method on the queries symbol. Which is kindof concurs with why it was strange for me.
我尝试使用花括号,但这又产生了另一个错误:
I tried using curly braces, but that gives another error:
2.0.0-p247 :023 > s[:query_volume].update_sql{:queries => :queries + 3}
SyntaxError: (irb):23: syntax error, unexpected =>, expecting '}'
s[:query_volume].update_sql{:queries => :queries + 3}
^
from /Users/avandra/.rvm/rubies/ruby-2.0.0-p247/bin/irb:16:in `<main>'
并使用
2.0.0-p247 :033 > s[:query_volume].update_sql{queries = queries + 3}
=> "UPDATE `query_volume` SET "
只是给出了格式错误的SQL ...
just gives a badly formatted SQL...
有人可以阐明如何做到这一点吗?
Could anyone shed some light on how this can be done?
推荐答案
You should use Sequel.expr
for that:
s[:query_volume].update_sql(:queries => Sequel.expr(3) + :queries)
这篇关于续集宝石增量的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!