大约有 13,000 项符合查询结果（耗时：0.0372秒） [XML]
Selecting only numeric columns from a data frame
...traightforward, and robust to use on database-back-ended tibbles:
dplyr::select_if(x, is.numeric)
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Check if value exists in Postgres array
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Simpler with the ANY construct:
SELECT value_variable = ANY ('{1,2,3}'::int[])
The right operand of ANY (between parentheses) can either be a set (result of a subquery, for instance) or an array. There are several ways to use it:
SQLAlchemy: how to filt...
java.sql.SQLException: Incorrect string value: '\xF0\x9F\x91\xBD\xF0\x9F…'
...e basic multilingual plane. They cannot be even represented in java as one char, "????????".length() == 4. They are definitely not null characters and one will see squares if you are not using fonts that support them.
MySQL's utf8 only supports basic multilingual plane, and you need to use utf8mb4 ...
Insert the carriage return character in vim
...tored a file in Unix ( \n newlines). I need to insert the carriage return character ( U+000D aka \r ). When I try to paste it from the clipboard ( "+p ) or type it using Ctrl + Shift + u - 000d , the linefeed is inserted ( U+000A ).
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How to retrieve the current value of an oracle sequence without increment it?
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SELECT last_number
FROM all_sequences
WHERE sequence_owner = '<sequence owner>'
AND sequence_name = '<sequence_name>';
You can get a variety of sequence metadata from user_sequences, all_sequences and dba_...
how do I query sql for a latest record date for each user
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select t.username, t.date, t.value
from MyTable t
inner join (
select username, max(date) as MaxDate
from MyTable
group by username
) tm on t.username = tm.username and t.date = tm.MaxDate
...
How can I convert tabs to spaces in every file of a directory?
...s on each line;
-t 4 means that each tab will be converted to 4 whitespace chars (8 by default).
sponge is from the moreutils package, and avoids clearing the input file.
Finally, you can use gexpand on OSX, after installing coreutils with Homebrew (brew install coreutils).
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How to randomly select an item from a list?
...ults, but depending on the start seed, it's not guaranteed. If you want to select n distinct random elements from a list lst, use random.sample(lst, n)
– Graham
Dec 23 '18 at 17:02
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How to initialize a struct in accordance with C programming language standards
...lize a struct this way:
typedef struct Item {
int a;
float b;
char* name;
} Item;
int main(void) {
Item item = { 5, 2.2, "George" };
return 0;
}
An important thing to remember, at the moment you initialize even one object/ variable in the struct, all of its other variables wi...
How to best display in Terminal a MySQL SELECT returning too many fields?
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Terminate the query with \G in place of ;. For example:
SELECT * FROM sometable\G
This query displays the rows vertically, like this:
*************************** 1. row ***************************
Host: localhost
Db: mydatabase1
...