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When should I use a composite index?
...nefit a query that uses those fields for joining, filtering, and sometimes selecting. It will also benefit queries that use left-most subsets of columns in that composite. So the above index will also satisfy queries that need
index( column_A, column_B, column_C )
index( column_A, column_B )
index(...
C# SQL Server - Passing a list to a stored procedure
...StringList READONLY
AS
BEGIN
-- Just return the items we passed in
SELECT l.Item FROM @list l;
END
Finally here's some sql to use it in c#:
using (var con = new SqlConnection(connstring))
{
con.Open();
using (SqlCommand cmd = new SqlCommand("exec sp_UseStringList @list", con))
...
SQL UPDATE SET one column to be equal to a value in a related table referenced by a different column
...result set to update is before running the update (same query, just with a select):
select *
from QuestionTrackings q
inner join QuestionAnswers a
on q.AnswerID = a.AnswerID
where q.QuestionID is null -- and other conditions you might want
Particularly whether each answer id has definitely only 1...
Drop columns whose name contains a specific string from pandas DataFrame
...
Use the DataFrame.select method:
In [38]: df = DataFrame({'Test1': randn(10), 'Test2': randn(10), 'awesome': randn(10)})
In [39]: df.select(lambda x: not re.search('Test\d+', x), axis=1)
Out[39]:
awesome
0 1.215
1 1.247
2 0.142
3...
How do MySQL indexes work?
...be faster to go through the pages one by one (in a database, this is "poor selectivity").
For a 10-page book, it makes no sense to make an index, as you may end up with a 10-page book prefixed by a 5-page index, which is just silly - just scan the 10 pages and be done with it.
The index also needs t...
How to write a simple Html.DropDownListFor()?
...%= Html.DropDownListFor(n => n.MyColorId,
new SelectList(Colors, "ColorId", "Name")) %>
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How to automatically generate getters and setters in Android Studio
...ar -> Code -> Generate...
and then using shift or control button, select all the variables you need to add getters and setters
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Xcode duplicate line
... command item as the screenshot below (name them what you want):
That's: selectLine:, copy:, moveToEndOfLine:, insertNewline:, paste:, deleteBackward:
Restart Xcode and go to Preferences - Key Bindings, search for your command.
Set a key combination for the command:
Finally unleashed the power of...
Programmatically scroll to a specific position in an Android ListView
...
For a direct scroll:
getListView().setSelection(21);
For a smooth scroll:
getListView().smoothScrollToPosition(21);
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How can I select an element by name with jQuery?
...
You can use the jQuery attribute selector:
$('td[name ="tcol1"]') // matches exactly 'tcol1'
$('td[name^="tcol"]' ) // matches those that begin with 'tcol'
$('td[name$="tcol"]' ) // matches those that end with 'tcol'
$('td[name*="tcol"]' ) // matche...