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Select Pandas rows based on list index
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For large datasets, it is memory efficient to read only selected rows via the skiprows parameter.
Example
pred = lambda x: x not in [1, 3]
pd.read_csv("data.csv", skiprows=pred, index_col=0, names=...)
This will now return a DataFrame from a file that skips all rows except 1 and ...
Linq to Entities join vs groupjoin
...Join syntax would be
from p in Parent
join c in Child on p.Id equals c.Id
select new { p.Value, c.ChildValue }
returning an IEnumerable<X> where X is an anonymous type with two properties, Value and ChildValue. This query syntax uses the Join method under the hood.
GroupJoin syntax would be
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How to get last N records with activerecord?
...e-wise - at least not up to Rails 3.1. SomeModel.last(5) will execute the select statement without a limit, returning all records of SomeModel to Ruby as an array, after which Ruby will pick out the last (5) elements. Efficiency-wise, currently, you want to use limit - particularly if you have pote...
how can I Update top 100 records in sql server
...derived table to define the desired sort order as below.
;WITH CTE AS
(
SELECT TOP 100 *
FROM T1
ORDER BY F2
)
UPDATE CTE SET F1='foo'
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What columns generally make good indexes?
...earching the results speedily from tables. So it is most important step to select which columns to be indexed. There are two major places where we can consider indexing: columns referenced in the WHERE clause and columns used in JOIN clauses. In short, such columns should be indexed against which yo...
Mysql: Select rows from a table that are not in another
How to select all rows in one table that do not appear on another?
8 Answers
8
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How to get Last record from Sqlite?
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Try this:
SELECT *
FROM TABLE
WHERE ID = (SELECT MAX(ID) FROM TABLE);
OR
you can also used following solution:
SELECT * FROM tablename ORDER BY column DESC LIMIT 1;
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How to select html nodes by ID with jquery when the id contains a dot?
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@Tomalak in comments:
since ID selectors must be preceded by a hash #, there should be no ambiguity here
“#id.class” is a valid selector that requires both an id and a separate class to match; it's valid and not always totally redundant.
The correct...
JUnit 4 Test Suites
...lipse:
In the 'Package Explorer' view of the eclipse 'Java' perspective,
select your unit test(s) in their package, inside the eclipse java
project.
Right-click on any one of the selected tests.
In the pop-up menu, select New, Other…
Open the ‘Java’ folder, then open the ‘JUnit’ folder...
Copying data from one SQLite database to another
...rt Into commands for the tables you want to transfer.
INSERT INTO X.TABLE SELECT * FROM Y.TABLE;
Or, if the columns are not matched up in order:
INSERT INTO X.TABLE(fieldname1, fieldname2) SELECT fieldname1, fieldname2 FROM Y.TABLE;
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