Get unique values from a list in python - Stack Overflow
2012年10月15日 · def getUnique(self): notunique = self.readLines() unique = [] for line in notunique: # Loop over content append = True # Will be set to false if line matches existing line for existing in unique: if line == existing: # Line exists ? do not append and go to the next line append = False break # Already know file is unique, break loop if append ...
database - How to select unique records by SQL - Stack Overflow
Option 4: Common Table Expression with ROW_NUMBER () In the Common Table Expression (CTE), select the ROW_NUMBER (), partitioned by the group column and ordered in the desired order. Then SELECT only the records that have ROW_NUMBER() = 1: WITH CTE AS (. SELECT *. ,row_number() OVER(PARTITION BY word, num ORDER BY id) AS row_num. FROM dupes.
List unique values in a Pandas dataframe - Stack Overflow
2017年12月22日 · You can get the unique values in the whole df with this one-liner: pd.Series(df.values.flatten()).unique() You basically transform your df to a numpy array, flatten and come back to a pandas Series, so you can use unique(). However, types might be transformed along the way if you have multiple types in your original df, so be careful.
python - pandas unique values multiple columns - Stack Overflow
297. pd.unique returns the unique values from an input array, or DataFrame column or index. The input to this function needs to be one-dimensional, so multiple columns will need to be combined. The simplest way is to select the columns you want and then view the values in a flattened NumPy array. The whole operation looks like this:
sql - Allow null in unique column - Stack Overflow
create unique index on MMCompany((email is null)) where (email is null); Another approach is to define a constraint trigger. Something like: create function email_chk() returns trigger as $$. begin. if exists (. select 1 from mmcompany where email is null and companyuniqueid <> new.id. ) then. raise 'dup null found';
retrieve unique hotel id for users for booking system
It would drive me nuts to have to move rooms every day! However, that aside, another way to conceptualize your problem is to look for and then exclude any hotels that have less than the required number of rooms between those dates. A calendar table, holding all relevant dates, may be useful for this. –
Entity Framework Core add unique constraint code-first
Since Entity Framework Core (EF Core) 5.0 we can configure Unique Indexes via Data Annotations. It is little different to e.g. EF6, because we cannot set it on the property itself but instead on the class. [Index(nameof(EmailAddress), IsUnique = true)] public class User. [Key] public Guid Id { get; set; }
Difference between primary key and unique key - Stack Overflow
2022年11月24日 · 1. Behavior: Primary Key is used to identify a row (record) in a table, whereas Unique-key is to prevent duplicate values in a column (with the exception of a null entry). 2. Indexing: By default SQL-engine creates Clustered Index on primary-key if not exists and Non-Clustered Index on Unique-key. 3.
How do I pass a unique_ptr argument to a constructor or a function?
2011年11月14日 · The proper way to do this is with the std::move standard library function. If you take a unique_ptr by value, you can move from it freely. But movement doesn't actually happen because of std::move. Take the following statement: std::unique_ptr<Base> newPtr(std::move(oldPtr)); This is really two statements:
Does unique_ptr::release () call the destructor? - Stack Overflow
2017年7月26日 · It is not, and will leak. release() just lets go of the memory ownership that this unique_ptr held until it was called, and returns a pointer that the caller now is responsible for, including having to manually delete it. If you don't assign the pointer returned by release(), you'll just have a leak.