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Pandas groupby: How to get a union of strings
I have a dataframe like this:
8 Answers
8
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Difference between 'struct' and 'typedef struct' in C++?
...different categories of identifiers, including tag identifiers (for struct/union/enum) and ordinary identifiers (for typedef and other identifiers).
If you just said:
struct Foo { ... };
Foo x;
you would get a compiler error, because Foo is only defined in the tag namespace.
You'd have to dec...
How to get HttpClient to pass credentials along with the request?
I have a web application (hosted in IIS) that talks to a Windows service. The Windows service is using the ASP.Net MVC Web API (self-hosted), and so can be communicated with over http using JSON. The web application is configured to do impersonation, the idea being that the user who makes the reques...
Can you create nested WITH clauses for Common Table Expressions?
...:
WITH y
AS
(
SELECT x, y, z
FROM MyTable
WHERE [base_condition]
UNION ALL
SELECT x, y, z
FROM MyTable M
INNER JOIN y ON M.[some_other_condition] = y.[some_other_condition]
)
SELECT *
FROM y
You may not need this functionality. I've done the following just to organize my queries ...
MySQL SELECT only not null values
...g it though...
SELECT val1 AS val
FROM your_table
WHERE val1 IS NOT NULL
UNION ALL
SELECT val2
FROM your_table
WHERE val2 IS NOT NULL
/*And so on for all your columns*/
The disadvantage of the above is that it scans the table multiple times once for each column. That may possibly be avoided by...
Keeping it simple and how to do multiple CTE in a query
...cte2 AS
(
SELECT 2 AS id
)
SELECT *
FROM cte1
UNION ALL
SELECT *
FROM cte2
UNION ALL
SELECT *
FROM cte1
Note, however, that SQL Server may reevaluate the CTE each time it is accessed, so if you are using values like RAND(), NEWID() etc., they may change between...
Oracle nvarchar和varchar相互转换、联合查询 - 数据库(内核) - 清泛网 - ...
...racle nvarchar和varchar相互转换、联合查询场景：联合查询（union all）Oracle两张表，同一组字段的数据类型不一致，分别是nvarchar和varchar。这时联合查询报错如下：ora12704：字...场景：联合查询（union all）Oracle两张表，同一组字段的...
ASP.NET 4.5 has not been registered on the Web server
...IS-ASPNET45" in "Turn Windows Features On/Off" under "Internet Information Services-> World Wide Web Services -> Application Development Features -> ASP.NET 4.5".
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T-SQL: Deleting all duplicate rows but keeping one [duplicate]
...g. the following is valid select min(id) from ( select newid() as id union select newid() as id ) as a
– iCodeSometime
Nov 15 '18 at 22:41
...
What is the difference between “INNER JOIN” and “OUTER JOIN”?
...Venn diagram intersection.
An outer join of A and B gives the results of A union B, i.e. the outer parts of a Venn diagram union.
Examples
Suppose you have two tables, with a single column each, and data as follows:
A B
- -
1 3
2 4
3 5
4 6
Note that (1,2) are unique to A, (3,...