sqlite3 gem的#execute和#query方法的返回值 [英] Return Values of #execute and #query methods of sqlite3 gem

问题描述

我正在sqlite3 gem的帮助下在ruby中使用sqlite3数据库(我试图在不使用ActiveRecords的情况下更好地了解使用sqlite3 gem).我在下面有一个SQL查询:

I am working with sqlite3 database in ruby with the help of sqlite3 gem (I'm trying to gain a better understanding of using sqlite3 gem without the use of ActiveRecords). I have an sql query below:

SELECT id FROM contacts WHERE first_name = 'Charles'

我希望它从中返回值'5'

From which I'm expecting it to return the value '5'

$db.execute('SELECT id FROM contacts WHERE first_name = ?', 'Charles') do |result|
  puts result
end

以上将打印"5"，但将返回一个sqlite3对象.我似乎无法获得execute方法来返回值"5".

Above will print '5', but will return an sqlite3 object. I couldn't seem to get the execute method to return the value '5'.

$db.query('SELECT id FROM contacts WHERE first_name = ?', 'Charles') do |result|
  result.first.first
end

我能得到的最接近的方法是使用query方法返回值"5"(见上)，但这需要.first.first似乎很复杂.

The closest I could get is to use the query method to return the value '5' (above), but this requires .first.first which seems convoluted.

我是否有更好的方法来获得所需的价值?即可能通过访问sqlite3对象?

Is there a better way for me to get the value I needed? i.e. perhaps through accessing the sqlite3 object?

推荐答案

尝试这个

$db.results_as_hash = true
$db.execute('SELECT id FROM contacts WHERE first_name = ?', 'Charles') do |row|
  puts row['id']
end

您需要一种方法.做类似的东西

You want a method. Make something like

def find_id_by_first_name(first_name)
  $db.results_as_hash = true
  $db.execute('SELECT id FROM contacts WHERE first_name = ?', first_name) do |row|
    return row['id']
  end
end

但是无论如何，您的查询可能有问题.如果first_name没有唯一索引，则此查询可能返回多个行.因此，这种方法没有太大意义.这只会返回第一个匹配结果.

But anyway, you could have a problem with your query. If first_name has not a unique index, this query could return more than one row. So this method doesn't make so much sense. This just returns the first matching result.

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