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Applying a function to every row of a table using dplyr?
...o create an appropriately vectorised function.
R provide pmax which is suitable here, however it also provides Vectorize as a wrapper for mapply to allow you to create a vectorised arbitrary version of an arbitrary function.
library(dplyr)
# use base R pmax (vectorized in C)
iris %>% mutate(max...
In where shall I use isset() and !empty()
...nd the answer is:
$var = "";
var_dump(isset($var));
The type comparison tables in PHP’s manual is quite handy for such questions.
isset basically checks if a variable has any value other than null since non-existing variables have always the value null. empty is kind of the counter part to iss...
Can I create a One-Time-Use Function in a Script or Stored Procedure?
...s like:
create procedure #mytemp as
begin
select getdate() into #mytemptable;
end
in an SQL script, but not functions. You could have the proc store it's result in a temp table though, then use that information later in the script ..
...
When to use single quotes, double quotes, and backticks in MySQL
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Backticks are to be used for table and column identifiers, but are only necessary when the identifier is a MySQL reserved keyword, or when the identifier contains whitespace characters or characters beyond a limited set (see below) It is often recommende...
How do I get the last inserted ID of a MySQL table in PHP?
I have a table into which new data is frequently inserted. I need to get the very last ID of the table. How can I do this?
...
How do you do a limit query in JPQL or HQL?
...
// SQL: SELECT * FROM table LIMIT start, maxRows;
Query q = session.createQuery("FROM table");
q.setFirstResult(start);
q.setMaxResults(maxRows);
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Finding duplicate values in a SQL table
...till requires all non-aggregated columns in the GROUP BY.
MySQL is unpredictable and you need sql_mode=only_full_group_by:
GROUP BY lname ORDER BY showing wrong results;
Which is the least expensive aggregate function in the absence of ANY() (see comments in accepted answer).
Oracle isn't mainstr...
How to put more than 1000 values into an Oracle IN clause [duplicate]
...
Put the values in a temporary table and then do a select where id in (select id from temptable)
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fol...
Comparing two dataframes and getting the differences
... behaviour for pd.concat(), here's the docs pandas.pydata.org/pandas-docs/stable/merging.html
– Thanos
Apr 17 '16 at 18:35
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How do you query for “is not null” in Mongo?
...ta set like my sample) that rather than using an index, MongoDB will use a table scan, even for a potential covered index query. As it turns out that gives me an easy way to illustrate the difference here:
db.foo.find({}, {_id : 0, imageUrl : 1})
{ "imageUrl" : "http://example.com/foo.jpg" }
{ "im...