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SQL: How to properly check if a record exists
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I would prefer not use Count function at all:
IF [NOT] EXISTS ( SELECT 1 FROM MyTable WHERE ... )
<do smth>
For example if you want to check if user exists before inserting it into the database the query can look like this:
IF NOT EXISTS ( SELECT 1 ...
Extracting specific columns from a data frame
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Using the dplyr package, if your data.frame is called df1:
library(dplyr)
df1 %>%
select(A, B, E)
This can also be written without the %>% pipe as:
select(df1, A, B, E)
share
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When to use transclude 'true' and transclude 'element' in Angular?
...le the content of the element and make it available to the directive. Typically used with ngTransclude. The advantage of transclusion is that the linking function receives a transclusion function which is pre-bound to the correct scope. In a typical setup the widget creates an isolate scope, but the...
Check if list contains element that contains a string and get that element
...plement them), as I'm not familiarized with it. What I would like to, basically, is this:
12 Answers
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How will I know when to create an interface?
...t solves this concrete problem:
you have a, b, c, d of 4 different types. all over your code you have something like:
a.Process();
b.Process();
c.Process();
d.Process();
why not have them implement IProcessable, and then do
List<IProcessable> list;
foreach(IProcessable p in list)
p.P...
Group by in LINQ
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Absolutely - you basically want:
var results = from p in persons
group p.car by p.PersonId into g
select new { PersonId = g.Key, Cars = g.ToList() };
Or as a non-query expression:
var results = persons.GroupBy(
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Favicon dimensions? [duplicate]
...fari, etc.), you need to combine both types of icons.
favicon.ico
Although all desktop browsers can deal with this icon, it is primarily for older version of IE.
The ICO format is different of the PNG format. This point is tricky because some browsers are smart enough to process a PNG picture correc...
'innerText' works in IE, but not in Firefox
...current beta release, and has been in aurora for a while. What this practically means is you can start developing sites using innerText only and expect it to work (with possible quirks) on all current browsers in the near future, and old-IE too.
– Bob
Feb 22 '1...
Why do we need RESTful Web Services?
...ng this low level of coupling is not easy to do. It is critical to follow all of the constraints of REST to succeed. Maintaining a purely stateless connection is difficult. Picking the right media-types and squeezing your data into the formats is tricky. Creating your own media types can be even...
Call by name vs call by value in Scala, clarification needed
As I understand it, in Scala, a function may be called either
16 Answers
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