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Concatenate multiple result rows of one column into one, group by another column [duplicate]
...Simpler with the aggregate function string_agg() (Postgres 9.0 or later):
SELECT movie, string_agg(actor, ', ') AS actor_list
FROM tbl
GROUP BY 1;
The 1 in GROUP BY 1 is a positional reference and a shortcut for GROUP BY movie in this case.
string_agg() expects data type text as input. Other ...
How do I set a variable to the output of a command in Bash?
...-expanded before being passed to the echo command.
– Charles Duffy
Apr 21 '15 at 15:37
4
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Program only crashes as release build — how to debug?
...sh do an Attach To Process (Tools menu on Visual Studio).
After the crash, select the option to launch debugger.
When asked to point to PDB files, browse to find them. If the PDB's were put in the same output folder as your E
How can I indent multiple lines in Xcode?
When I select multiple lines of code and want to indent them as usual with TAB key, it just deletes them all. I come from Eclipse where I always did it that way. How's that done in Xcode? I hope not line by line ;)
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Apache2: 'AH01630: client denied by server configuration'
...activity)
In activity monitor search for httpd which is the Apache service
Select the one that belongs to root and click X on the top left to close it.
At that point I immediately stopped getting 403 errors and everything started working as expected. Weird thing is i didn't even have to restart ap...
Can you run GUI applications in a Docker container?
... How would I use a VNC client to view this remotely? Typing in the IP + port doesn't seem to be working.
– user94154
Jul 30 '13 at 0:42
17
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MySQL Conditional Insert
...
If your DBMS does not impose limitations on which table you select from when you execute an insert, try:
INSERT INTO x_table(instance, user, item)
SELECT 919191, 123, 456
FROM dual
WHERE NOT EXISTS (SELECT * FROM x_table
WHERE user = ...
string.IsNullOrEmpty(string) vs. string.IsNullOrWhiteSpace(string)
...
The best practice is selecting the most appropriate one.
.Net Framework 4.0 Beta 2 has a new IsNullOrWhiteSpace() method for
strings which generalizes the IsNullOrEmpty() method to also include other white
space besides empty string.
...
Best practices for SQL varchar column length [closed]
...hen you need to worry about it and make them smaller. But if you only ever select 1 row from that table, then you can just make them all 255 and it won't matter.
See: What are the optimum varchar sizes for MySQL?
share
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What is the copy-and-swap idiom?
...y that, but unqualified calls to swap will use our custom swap operator, skipping over the unnecessary construction and destruction of our class that std::swap would entail.)
An in-depth explanation
The goal
Let's consider a concrete case. We want to manage, in an otherwise useless class, a dyn...