大约有 43,000 项符合查询结果（耗时：0.0482秒） [XML]
Postgres: Distinct but only for one column
...h names (having more than 1 mio. rows), but I have also many duplicates. I select 3 fields: id , name , metadata .
3 Ans...
Random row selection in Pandas dataframe
Is there a way to select random rows from a DataFrame in Pandas.
6 Answers
6
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How can I check if a View exists in a Database?
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FOR SQL SERVER
IF EXISTS(select * FROM sys.views where name = '')
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MySQL dump by query
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not mysqldump, but mysql cli...
mysql -e "select * from myTable" -u myuser -pxxxxxxxxx mydatabase
you can redirect it out to a file if you want :
mysql -e "select * from myTable" -u myuser -pxxxxxxxx mydatabase > mydumpfile.txt
Update:
Original post asked if...
General guidelines to avoid memory leaks in C++ [closed]
...tion will have a buffer "on the stack of the class" for small strings (~15 chars), and will use a pointer to a memory in the heap for larger strings... But from the outside, std::string is still a value type that you declare (usually) on the stack and you use as you would use an integer (as opposed ...
java.lang.ClassNotFoundException: org.springframework.web.context.ContextLoaderListener
...rties (e.g., right-click on the project's name in the project explorer and select "Properties").
Select "Deployment Assembly".
Click the "Add..." button on the right margin.
Select "Java Build Path Entries" from the menu of Directive Type and click "Next".
Select "Maven Dependencies" from the Java B...
Strange SQLAlchemy error message: TypeError: 'dict' object does not support indexing
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This should be the selected answer. It solved the issue in my case.
– Gani Simsek
Feb 20 '17 at 13:11
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When to use Vanilla JavaScript vs. jQuery?
...now)
this.value (on most input types. only issues I know are IE when a <select> doesn't have value properties set on its <option> elements, or radio inputs in Safari.)
this.className to get or set an entire "class" property
this.selectedIndex against a <select> to get the selected ...
Throwing the fattest people off of an overloaded airplane.
...uch better. I use something quite like this for a recommendation engine (I select the top 200 items from a list of several million). I typically end up with only 50,000 or 70,000 items actually added to the heap.
I suspect that you'll see something quite similar: the majority of your candidates wil...
Regular expression to match DNS hostname or IP Address?
...check separately that the total length of the hostname must not exceed 255 characters. For more information, please consult RFC-952 and RFC-1123.
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