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What is the string concatenation operator in Oracle?
...' = 'x' makes sense. But if you think of null as "undefined" or "unknown" then 'x' || null could be any string beginning with 'x' and so is itself "unknown"!
– Tony Andrews
Nov 10 '08 at 16:02
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SQL join: selecting the last records in a one-to-many relationship
... date (or in the case of ties, a later id). When we find that to be true, then p1 is the most recent purchase for that customer.
Regarding indexes, I'd create a compound index in purchase over the columns (customer_id, date, id). That may allow the outer join to be done using a covering index. B...
Precise Financial Calculation in JavaScript. What Are the Gotchas?
... been tested in production at scale.. Just pointing that out so anyone can then consider if that's appropriate for their use case
– Nobita
Oct 17 '19 at 7:59
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How to detect duplicate values in PHP array?
...al array in PHP. I would like to detect the presence of duplicate values, then count the number of duplicate values and out put the results. For example, given the following array:
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How to round up to the nearest 10 (or 100 or X)?
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If you just want to round up to the nearest power of 10, then just define:
roundUp <- function(x) 10^ceiling(log10(x))
This actually also works when x is a vector:
> roundUp(c(0.0023, 3.99, 10, 1003))
[1] 1e-02 1e+01 1e+01 1e+04
..but if you want to round to a "nice" nu...
Copying PostgreSQL database to another server
... drop database y, use the "or" part of Ferran's solution which restores x, then rename the database to y.
– Darin Peterson
Mar 4 '14 at 16:28
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What's the difference between @JoinColumn and mappedBy when using a JPA @OneToMany association
...hich references Company, but the underlying table has a column which does, then you can use @JoinTable to map it. This is an unusual situation, because you would normally map the column in the object which corresponds to its table, but it can happen, and it is perfectly legitimate.
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How can you debug a CORS request with cURL?
...m/ with URL you want to test.
If response includes Access-Control-Allow-* then your resource supports CORS.
Rationale for alternative answer
I google this question every now and then and the accepted answer is never what I need. First it prints response body which is a lot of text. Adding --hea...
Remove rows with duplicate indices (Pandas DataFrame and TimeSeries)
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This adds the index as a dataframe column, drops duplicates on that, then removes the new column:
df = df.reset_index().drop_duplicates(subset='index', keep='last').set_index('index').sort_index()
Note that the use of .sort_index() above at the end is as needed and is optional.
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REST API Token-based Authentication
I'm developing a REST API that requires authentication. Because the authentication itself occurs via an external webservice over HTTP, I reasoned that we would dispense tokens to avoid repeatedly calling the authentication service. Which brings me neatly to my first question:
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