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Remove an entire column from a data.frame in R
... long amount of time and/or fail due to out of memory errors. Package data.table helps address this problem with the := operator:
library(data.table)
> dt <- data.table(a = 1, b = 1, c = 1)
> dt[,a:=NULL]
b c
[1,] 1 1
I should put together a bigger example to show the differences. I...
MySQL Query to select data from last week?
Hi I have a table with a date field and some other information.
I want to select all entries from the past week, (week start from Sunday).
...
Check for column name in a SqlDataReader object
...elp anyone setting their debugger to break on exceptions thrown.
GetSchemaTable() is also another suggestion in many answers. This would not be a preffered way of checking for a field's existance as it is not implemented in all versions (it's abstract and throws NotSupportedException in some versio...
How do I limit the number of rows returned by an Oracle query after ordering?
...).
To answer the original question, here's the query:
SELECT *
FROM sometable
ORDER BY name
OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY;
(For earlier Oracle versions, please refer to other answers in this question)
Examples:
Following examples were quoted from linked page, in the hope of preventing ...
How do you use script variables in psql?
...nd can then be substituted, for example, as ...
SELECT * FROM :myvariable.table1;
... or ...
SELECT * FROM table1 WHERE :myvariable IS NULL;
edit: As of psql 9.1, variables can be expanded in quotes as in:
\set myvariable value
SELECT * FROM table1 WHERE column1 = :'myvariable';
In olde...
When and why will a compiler initialise memory to 0xCD, 0xDD, etc. on malloc/free/new/delete?
... Or that memory just has been freed by HeapFree().
Disclaimer: the table is from some notes I have lying around - they may not be 100% correct (or coherent).
Many of these values are defined in vc/crt/src/dbgheap.c:
/*
* The following values are non-zero, constant, odd, large, and atypica...
Custom Adapter for List View
...the row of the ListView.
<?xml version="1.0" encoding="utf-8"?>
<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="wrap_content" android:orientation="vertical"
android:layout_width="fill_parent">
<TableRow android:layout_width=...
How to make an inline-block element fill the remainder of the line?
...e using CSS and two inline-block (or whatever) DIV tags instead of using a table?
7 Answers
...
What is a columnar database?
...are build upon traditional, row-oriented, DBMS, simply storing the info in tables with one (or rather often two) columns (and adding the necessary layer to access the columnar data in an easy fashion).
How do they differ from relational databases?
They generally differ from traditional (row-oriente...
How do I obtain a Query Execution Plan in SQL Server?
...mat.
Notes:
Because there are so many factors involved (ranging from the table and index schema down to the data stored and the table statistics) you should always try to obtain an execution plan from the database you are interested in (normally the one that is experiencing a performance problem)....