if you are looking for all referers - try  

    SELECT date, h.referer
    FROM `refresh.ga_sessions_xxxxxx*`, UNNEST(hits) as h

How to navigate relative from `/questions/123/step1` to `/questions/123/step2` within a component using `Router` without string concatenation and specifying `/questions/123/`?

I&#39;ve added an own answer below. Please feel free to suggest a better answer. ;-) I guess there are better approaches.

Navigate relative with Angular 2 Router (Version 3)

I&#39;ve updated my code to Xcode 8.0 beta 6 but I got stuck with what seems to be about the new non escaping closure default. In the following code Xcode suggests to add `@escaping` in front of `completion:` in the first line of the below code, but that still won&#39;t compile and goes in circles. *


(**EDIT**: In fact, @escaping should be added in **after** `completion:`, as Xcode suggests. The alert may still show but cleaning and compiling will remove it.)* How should this code be re-written / fixed to work in the updated Swift 3?
I&#39;ve had a look in the new manual but I couldn&#39;t find proper code samples.

    func doSomething(withParameter parameter: Int, completion: () -&gt; ()) {
        // Does something
        
        callSomeOtherFunc(withCompletion: completion)
      }
    
    // Calling the method and execute closure 
    doSomething(withParameter: 2) {
      // do things in closure
    }

Any help much appreciated!

Updating closures to Swift 3 - @escaping

I&#39;m trying to run a query using Standard SQL Dialect (ie not Legacy SQL) on BigQuery. My query is:

    SELECT
    date, hits.referer
    FROM `refresh.ga_sessions_xxxxxx*`
    LIMIT 1000

But keep getting the error 

    Error: Cannot access field referer on a value with type 
    ARRAY&lt;STRUCT&lt;hitNumber INT64, time INT64, hour INT64, ...&gt;&gt; at [2:12]

Anyone know the proper syntax? 

Cannot access field in Big Query with type ARRAY&lt;STRUCT&lt;hitNumber INT64, time INT64, hour INT64, ...&gt;&gt;

I'm trying to run a query using Standard SQL Dialect (ie not Legacy SQL) on BigQuery. My query is:
<pre><code class="hljs language-sql">SELECT
date, hits.referer
FROM `refresh.ga_sessions_xxxxxx*`
LIMIT 1000
</code></pre>
But keep getting the error
<pre><code class="hljs language-sql">Error: Cannot access field referer on a value with type 
ARRAY&#x3C;STRUCT&#x3C;hitNumber INT64, time INT64, hour INT64, ...>> at [2:12]
</code></pre>
Anyone know the proper syntax?

For example I have a file `customers.json` which is an array of objects (strictly formed) and it&#39;s pretty plain (without nested objects) like this (what is important: it&#39;s already include ids):

    [
      {
        &quot;id&quot;: 23635,
        &quot;name&quot;: &quot;Jerry Green&quot;,
        &quot;comment&quot;: &quot;Imported from facebook.&quot;
      },
      {
        &quot;id&quot;: 23636,
        &quot;name&quot;: &quot;John Wayne&quot;,
        &quot;comment&quot;: &quot;Imported from facebook.&quot;
      }
    ]

And I want to import them all into my postgres db into a table `customers`.

I found some pretty difficult ways when I should import it as json-typed column to a table like `imported_json` and column named `data` with objects listed there, then to use sql to get these values and insert it into a real table.

But is there a simple way of importing json to postgres with no touching of sql?

How can I import a JSON file into PostgreSQL?

I have a SQL query which perfroms a series of left joins on a few tables:

    SELECT
    &lt;some attributes&gt;
    FROM table1 t1
    INNER JOIN table2 t2
          ON attr = 1 AND attr2 = 1
	LEFT JOIN table3 t3
        ON t1.Code = t2.Code AND t3.Date_ = t1.Date_
	LEFT JOIN tabl4 t4
	    ON t4.Code = t1.code AND t4.Date_ = t1.Date_

So far, I have:

    (sa.select([idc.c.Code])
                .select_from(
                    t1.join(t2, and_(t1.c.attr == 1, t2.c.attr2 = 1))
                    .join(t3, t3.c.Code == t1.c.Code)))

but I can&#39;t figure out how to make the join a `LEFT JOIN`.

                    

How to perform a left join in SQLALchemy?

I&#39;m on presto and have a date formatted as varchar that looks like - 

    7/14/2015 8:22:39 AM

I&#39;ve looked the presto docs and tried various things(cast, date_format, using split_part to parse and then cast) and am not getting this to convert to a date format that I can use with functions like date_diff.

I&#39;ve tried:

    cast(fieldname as timestamp)
    date_format(fieldname, &#39;%Y-%m-%d %T)

Both give me an error like this 

    &#39;Value cannot be cast to timestamp: 3/31/2016 6:05:04 PM&#39;

How do I convert this?

Presto SQL - Converting a date string to date format

My requirement is write optional parameters to a function.Parameters are optional sometimes i will add or i will not pass parameters to function.Can anyone help me how to write function.

I am writing like 

    select * 
    from test 
    where field3 in (&#39;value1&#39;,&#39;value2&#39;) 
     and ($1 is null or field1 = $1) 
     and ($2 is null or field2 = $2) 
     and ($3 is null or field3 = $3);

i am passing parameters to Query,But my output is not expected.when i pass all three parameters my output is correct,otherwise it is not expected output.


How to write function for optional parameters in postgresql?

I try to map my other DB to a user by going to &lt;br/&gt;Security &gt; Logins &gt; right click someuser &gt; Properties &gt; User Mapping &gt; Select DB &gt; set as db_owner and then ok, but I keep on getting an error saying 

&gt; User, group, or role &#39;someuser&#39; already exists in the current database. (Microsoft SQL Server, Error: 15023)

What is causing the error, and how do I map that user to the database? 

SQL Server User Mapping Error 15023

I am currently struggling with nesting routes using react router v4.

The closest example was the route config in the 
[React-Router v4 Documentation][1].

I want to split my app in 2 different parts.

A frontend and an admin area.

I was thinking about something like this:

    &lt;Match pattern=&quot;/&quot; component={Frontpage}&gt;
      &lt;Match pattern=&quot;/home&quot; component={HomePage} /&gt;
      &lt;Match pattern=&quot;/about&quot; component={AboutPage} /&gt;
    &lt;/Match&gt;
    &lt;Match pattern=&quot;/admin&quot; component={Backend}&gt;
      &lt;Match pattern=&quot;/home&quot; component={Dashboard} /&gt;
      &lt;Match pattern=&quot;/users&quot; component={UserPage} /&gt;
    &lt;/Match&gt;
    &lt;Miss component={NotFoundPage} /&gt;

The frontend has a different layout and style than the admin area. So within the frontpage the route home, about and so one should be the child routes.

**/home** should be rendered into the Frontpage component and **/admin/home** should be rendered within the Backend component. 

I tried some variations but I always ended in not hitting /home or /admin/home.


**Edit - 19.04.2017**

Because this post has a lot of views right now I updated it with the final solution. I hope it helps someone.

**Edit - 08.05.2017**

Removed old solutions

**Final solution:**

This is the final solution I am using right now. This example also has a global error component like a traditional 404 page.


    import React, { Component } from &#39;react&#39;;
    import { Switch, Route, Redirect, Link } from &#39;react-router-dom&#39;;
    
    const Home = () =&gt; &lt;div&gt;&lt;h1&gt;Home&lt;/h1&gt;&lt;/div&gt;;
    const User = () =&gt; &lt;div&gt;&lt;h1&gt;User&lt;/h1&gt;&lt;/div&gt;;
    const Error = () =&gt; &lt;div&gt;&lt;h1&gt;Error&lt;/h1&gt;&lt;/div&gt;
    
    const Frontend = props =&gt; {
      console.log(&#39;Frontend&#39;);
      return (
        &lt;div&gt;
          &lt;h2&gt;Frontend&lt;/h2&gt;
          &lt;p&gt;&lt;Link to=&quot;/&quot;&gt;Root&lt;/Link&gt;&lt;/p&gt;
          &lt;p&gt;&lt;Link to=&quot;/user&quot;&gt;User&lt;/Link&gt;&lt;/p&gt;
          &lt;p&gt;&lt;Link to=&quot;/admin&quot;&gt;Backend&lt;/Link&gt;&lt;/p&gt;
          &lt;p&gt;&lt;Link to=&quot;/the-route-is-swiggity-swoute&quot;&gt;Swiggity swooty&lt;/Link&gt;&lt;/p&gt;
          &lt;Switch&gt;
            &lt;Route exact path=&#39;/&#39; component={Home}/&gt;
            &lt;Route path=&#39;/user&#39; component={User}/&gt;
            &lt;Redirect to={{
              state: { error: true }
            }} /&gt;
          &lt;/Switch&gt;
          &lt;footer&gt;Bottom&lt;/footer&gt;
        &lt;/div&gt;
      );
    }
    
    const Backend = props =&gt; {
      console.log(&#39;Backend&#39;);
      return (
        &lt;div&gt;
          &lt;h2&gt;Backend&lt;/h2&gt;
          &lt;p&gt;&lt;Link to=&quot;/admin&quot;&gt;Root&lt;/Link&gt;&lt;/p&gt;
          &lt;p&gt;&lt;Link to=&quot;/admin/user&quot;&gt;User&lt;/Link&gt;&lt;/p&gt;
          &lt;p&gt;&lt;Link to=&quot;/&quot;&gt;Frontend&lt;/Link&gt;&lt;/p&gt;
          &lt;p&gt;&lt;Link to=&quot;/admin/the-route-is-swiggity-swoute&quot;&gt;Swiggity swooty&lt;/Link&gt;&lt;/p&gt;
          &lt;Switch&gt;
            &lt;Route exact path=&#39;/admin&#39; component={Home}/&gt;
            &lt;Route path=&#39;/admin/user&#39; component={User}/&gt;
            &lt;Redirect to={{
              state: { error: true }
            }} /&gt;
          &lt;/Switch&gt;
          &lt;footer&gt;Bottom&lt;/footer&gt;
        &lt;/div&gt;
      );
    }
    
    class GlobalErrorSwitch extends Component {
      previousLocation = this.props.location
    
      componentWillUpdate(nextProps) {
        const { location } = this.props;
    
        if (nextProps.history.action !== &#39;POP&#39;
          &amp;&amp; (!location.state || !location.state.error)) {
            this.previousLocation = this.props.location
        };
      }
    
      render() {
        const { location } = this.props;
        const isError = !!(
          location.state &amp;&amp;
          location.state.error &amp;&amp;
          this.previousLocation !== location // not initial render
        )
    
        return (
          &lt;div&gt;
            {          
              isError
              ? &lt;Route component={Error} /&gt;
              : &lt;Switch location={isError ? this.previousLocation : location}&gt;
                  &lt;Route path=&quot;/admin&quot; component={Backend} /&gt;
                  &lt;Route path=&quot;/&quot; component={Frontend} /&gt;
                &lt;/Switch&gt;}
          &lt;/div&gt;
        )
      }
    }
    
    class App extends Component {
      render() {
        return &lt;Route component={GlobalErrorSwitch} /&gt;
      }
    }
    
    export default App;


  [1]: https://react-router.now.sh/



Nested routes with react router v4 / v5

I have a flattened dictionary which I want to make into a nested one, of the form

    flat = {&#39;X_a_one&#39;: 10,
            &#39;X_a_two&#39;: 20, 
            &#39;X_b_one&#39;: 10,
            &#39;X_b_two&#39;: 20, 
            &#39;Y_a_one&#39;: 10,
            &#39;Y_a_two&#39;: 20,
            &#39;Y_b_one&#39;: 10,
            &#39;Y_b_two&#39;: 20}

I want to convert it to the form

    nested = {&#39;X&#39;: {&#39;a&#39;: {&#39;one&#39;: 10,
                          &#39;two&#39;: 20}, 
                    &#39;b&#39;: {&#39;one&#39;: 10,
                          &#39;two&#39;: 20}}, 
              &#39;Y&#39;: {&#39;a&#39;: {&#39;one&#39;: 10,
                          &#39;two&#39;: 20},
                    &#39;b&#39;: {&#39;one&#39;: 10,
                          &#39;two&#39;: 20}}}

The structure of the flat dictionary is such that there should not be any problems with ambiguities. I want it to work for dictionaries of arbitrary depth, but performance is not really an issue. I&#39;ve seen lots of methods for flattening a nested dictionary, but basically none for nesting a flattened dictionary. The values stored in the dictionary are either scalars or strings, never iterables.

So far I have got something which can take the input 

    test_dict = {&#39;X_a_one&#39;: &#39;10&#39;,
                 &#39;X_b_one&#39;: &#39;10&#39;,
                 &#39;X_c_one&#39;: &#39;10&#39;}


to the output

    test_out = {&#39;X&#39;: {&#39;a_one&#39;: &#39;10&#39;, 
                      &#39;b_one&#39;: &#39;10&#39;, 
                      &#39;c_one&#39;: &#39;10&#39;}}

using the code

    def nest_once(inp_dict):
        out = {}
        if isinstance(inp_dict, dict):
            for key, val in inp_dict.items():
                if &#39;_&#39; in key:
                    head, tail = key.split(&#39;_&#39;, 1)

                    if head not in out.keys():
                        out[head] = {tail: val}
                    else:
                        out[head].update({tail: val})
                else:
                    out[key] = val
        return out
 
    test_out = nest_once(test_dict)

But I&#39;m having trouble working out how to make this into something which recursively creates all levels of the dictionary.

Any help would be appreciated!

(As for why I want to do this: I have a file whose structure is equivalent to a nested dict, and I want to store this file&#39;s contents in the attributes dictionary of a NetCDF file and retrieve it later. However NetCDF only allows you to put flat dictionaries as the attributes, so I want to unflatten the dictionary I previously stored in the NetCDF file.)

Creating a nested dictionary from a flattened dictionary

Can I use the same counter variable for a `for` loop inside of a `for` loop?

Or will the variables affect each other? Should the following code use a different variable for the second loop, such as `j`, or is `i` fine?

    for(int i = 0; i &lt; 10; i++)
    {
      for(int i = 0; i &lt; 10; i++)
      {
      }
    }


Can a &#39;for&#39; loop inside of a &#39;for&#39; loop use the same counter variable name?

 Is there any reason why someone would use Bigtable instead of BigQuery? Both seem to support Read and Write operations with the latter offering also advanced &#39;Query&#39; operations.

I need to develop an affiliate network (thus I need to track clicks and &#39;sales&#39;) so I&#39;m quite confused by the difference because BigQuery seems to be just Bigtable with a better API.

What&#39;s the difference between BigQuery and Bigtable?

A BigQuery [table][1] has schema which can be viewed in the web UI, [updated][2], or used to [load data][3] with the `bq` tool as a JSON file. However, I can&#39;t find a way to dump this schema from an existing table to a JSON file (preferably from the command-line). Is that possible?


  [1]: https://cloud.google.com/bigquery/docs/tables
  [2]: https://cloud.google.com/bigquery/docs/tables#updateschema
  [3]: https://cloud.google.com/bigquery/loading-data

Content Type	Original Author	Original Content on Stackoverflow
Question	Feynman27	View Question on Stackoverflow
Solution 1 - Sql	Mikhail Berlyant	View Answer on Stackoverflow

Cannot access field in Big Query with type ARRAY<STRUCT<hitNumber INT64, time INT64, hour INT64, ...>>

Sql Problem Overview

Sql Solutions

Solution 1 - Sql

Updating closures to Swift 3 - @escaping

Navigate relative with Angular 2 Router (Version 3)

Attributions