Newbie here. I am trying to store the result of my search onto a variable.
#answer = q.answers.select(:name) which runs
"SELECT name FROM "answers" WHERE "answers"."question_id" = 1;" and returns
"t" for true.
It runs fine on the command line and shows the right result. But I want to compare that result to another variable.
How do i extract that result? #answer[0], or #answer, or answer_var = #answer[0]
i.e.
if #answer == some_other_variable OR
if #answer[0] == some_other_variable OR
if answer_var == some_other_variable
what value do #answer[0] and #answer[0] hold and how can I print the value to the log file? not the web page. I know it must be simple, but I can't get my head around it.
Thanks.
It's not really an answer to your question but...
If you want to follow "the rails way", you should better use Models and not deal with SQL at all.
E.g. :
#answer = q.answers.first # answers is an array, take the first
if #answer.name == ...
For the logging, I suggest you that : http://guides.rubyonrails.org/debugging_rails_applications.html#the-logger
Related
I've not played with Ruby in a while, and was just writing a simple db query tool.
The tool connects fine and returns the correct number of results for the query (56 rows in this case), but the value returned for each element is 'nil'. Executing the query in sqlplus works fine.
I've found similar problems on StackExchange, but most of the solutions don't apply, or require using ODBC directly. Ugh.
I'm including a stripped down version of what I've written. Any ideas what I'm doing wrong?
require 'dbi'
dbh = DBI.connect('DBI:OCI8:foodb', 'user', 'password')
rs = dbh.prepare('select field_name from foo_user.cdr_fields where layout like ?')
rs.execute('phi_outage')
while rsRow = rs.fetch do
p rsRow
end
rs.finish
dbh.disconnect
The fetch method is an iterator so no need for a while loop. Try
rs.fetch do|row|
p row unless p.nil?
end
The API states that the method gets called for all remaining rows and will return nil when done.
I was looking at another question in stackoverflow regarding auto increment fields in orientdb, where one of the answers was to create our own vertex with counter field.
However, when I'm trying to execute the following code (both java api and console script batch), It is not working.
Do note however that the id is returned good (did some debug attempts, returning the id variable only), and the vertex is created.
However, the vertex id is always null (unless I set it explicit, that is).
The script:
script sql
LET id = UPDATE CCounter INCREMENT value=1 RETURN AFTER $current WHERE name='session'
LET csession = CREATE VERTEX CDate SET id=$id.result, meet_date='2015-01-01 15:23:00'
end
I tried playing around with $id and $current , but nothing seems to work.
Currently I am doing it in a 2-transaction mode; one to get the id, and another to create the vertex. I really hope there is a better way though.
P.S.
I am using version 2.0-M2
You should execute
LET csession = CREATE VERTEX CDate SET id=$id.value, meet_date='2015-01-01 15:23:00'
Note the $id.value in place of $id.result.
As stated in a comment to Lvca, the answer was:
(1) Change the field name. Id seems to be reserved (ish). It's probably possible to still bypass it and use a field named 'id', but I didn't want to mess around with it.
(2) From some reason, the result was a collection (shown as '[id]'). It took me some time to figure it out, but I just had to choose the first value from it.
(3) Also, there are 2 'values' here. One of the field ($current.value), and the second one(not sure where it's coming from).
Final solution that works:
script sql
LET id = UPDATE CCounter INCREMENT value = 1 RETURN AFTER $current.value WHERE name='session'
LET csession = CREATE VERTEX CDate SET data_id=$id[0].value, meet_date='2015-01-01 15:23:00'
end
I want to query a table and only need one cell returned. Right now the only way I can think to do it is:
$query = $this->db->query('SELECT id FROM crops WHERE name = "wheat"');
if ($query->num_rows() > 0) {
$row = $query->row();
$crop_id = $row->id;
}
What I want is, since I'm select 'id' anyway, for that to be the result. IE: $query = 'cropId'.
Any ideas? Is this even possible?
Of course it's possible. Just use AND in your query:
$query = $this->db->query('SELECT id FROM crops WHERE name = "wheat" AND id = {$cropId}');
Or you could use the raw power of the provided Active Record class:
$this->db->select('id');
$this->db->from('crops');
$this->db->where('name','wheat');
$this->db->where('id',$cropId);
$query = $this->db->get();
If you just want the cropId from the whole column:
foreach ($query->result()->id as $cropId)
{
echo $cropId;
}
Try this out, I'm not sure if it will work:
$cropId = $query->first_row()->id;
Note that you want to swap your quotes around: use " for your PHP strings, and ' for your SQL strings. First of all, it would not be compatible with PostgreSQL and other database systems that check such things.
Otherwise, as Christopher told you, you can test the crop identifier in your query. Only if you define a string between '...' in PHP, the variables are not going to be replaced in the strings. So he showed the wrong PHP code.
"SELECT ... $somevar ..."
will work better.
Yet, there is a security issue in writing such strings: it is very dangerous because $somevar could represent some additional SQL and completely transform your SELECT in something that you do not even want to think about. Therefore, the Active Record as mentioned by Christopher is a lot safer.
How do you work with the old values of a record being updated?
For instance in the following code block how would I run a query using the previous winner_id field after I determine that it has indeed changed?
if self.winner_id_changed?
old_value = self.changed_attributes
User.find(old_value)
#do stuff with the old winner....
end
An example output of self.changed_attributes would be:
{"winner_id"=>6}
Do I really have to convert this to a string and parse out the value in order to perform a query on it? old_value[:winner_id] doesn't seem to do anything.
Use where instead of find, and the following inject method on changes to generate the desired hash:
if self.winner_id_changed?
old_value = self.changes.inject({}) { |h, (k,v)| h[k] = v.first }
old_user = User.where(old_value)
#do stuff with the old user....
end
You can also use ActiveRecord dirty methods such as:
self.winner_id_was
to get specific attribute's old value. Full documentation may be found here.
Setting the DBIC_TRACE environment variable to true:
BEGIN { $ENV{DBIC_TRACE} = 1 }
generates very helpful output, especially showing the SQL query that is being executed, but the SQL query is all on one line.
Is there a way to push it through some kinda "sql tidy" routine to format it better, perhaps breaking it up over multiple lines? Failing that, could anyone give me a nudge into where in the code I'd need to hack to add such a hook? And what the best tool is to accept a badly formatted SQL query and push out a nicely formatted one?
"nice formatting" in this context simply means better than "all on one line". I'm not particularly fussed about specific styles of formatting queries
Thanks!
As of DBIx::Class 0.08124 it's built in.
Just set $ENV{DBIC_TRACE_PROFILE} to console or console_monochrome.
From the documentation of DBIx::Class::Storage
If DBIC_TRACE is set then trace information is produced (as when the
debug method is set). ...
debug Causes trace information to be emitted on the debugobj
object. (or STDERR if debugobj has not specifically been set).
debugobj Sets or retrieves the object used for metric collection.
Defaults to an instance of DBIx::Class::Storage::Statistics that is
compatible with the original method of using a coderef as a callback.
See the aforementioned Statistics class for more information.
In other words, you should set debugobj in that class to an object that subclasses DBIx::Class::Storage::Statistics. In your subclass, you can reformat the query the way you want it to be.
First, thanks for the pointers! Partial answer follows ....
What I've got so far ... first some scaffolding:
# Connect to our db through DBIx::Class
my $schema = My::Schema->connect('dbi:SQLite:/home/me/accounts.db');
# See also BEGIN { $ENV{DBIC_TRACE} = 1 }
$schema->storage->debug(1);
# Create an instance of our subclassed (see below)
# DBIx::Class::Storage::Statistics class
my $stats = My::DBIx::Class::Storage::Statistics->new();
# Set the debugobj object on our schema's storage
$schema->storage->debugobj($stats);
And the definition of My::DBIx::Class::Storage::Statistics being:
package My::DBIx::Class::Storage::Statistics;
use base qw<DBIx::Class::Storage::Statistics>;
use Data::Dumper qw<Dumper>;
use SQL::Statement;
use SQL::Parser;
sub query_start {
my ($self, $sql_query, #params) = #_;
print "The original sql query is\n$sql_query\n\n";
my $parser = SQL::Parser->new();
my $stmt = SQL::Statement->new($sql_query, $parser);
#printf "%s\n", $stmt->command;
print "The parameters for this query are:";
print Dumper \#params;
}
Which solves the problem about how to hook in to get the SQL query for me to "pretty-ify".
Then I run a query:
my $rs = $schema->resultset('SomeTable')->search(
{
'email' => $email,
'others.some_col' => 1,
},
{ join => 'others' }
);
$rs->count;
However SQL::Parser barfs on the SQL generated by DBIx::Class:
The original sql query is
SELECT COUNT( * ) FROM some_table me LEFT JOIN others other_table ON ( others.some_col_id = me.id ) WHERE ( others.some_col_id = ? AND email = ? )
SQL ERROR: Bad table or column name '(others' has chars not alphanumeric or underscore!
SQL ERROR: No equijoin condition in WHERE or ON clause
So ... is there a better parser than SQL::Parser for the job?