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SQL set values of one column equal to values of another column in the same table
I have a table with two DATETIME columns.
5 Answers
5
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MySQL - SELECT WHERE field IN (subquery) - Extremely slow why?
...
Rewrite the query into this
SELECT st1.*, st2.relevant_field FROM sometable st1
INNER JOIN sometable st2 ON (st1.relevant_field = st2.relevant_field)
GROUP BY st1.id /* list a unique sometable field here*/
HAVING COUNT(*) > 1
I think st2.relevant_field must be in the select, because other...
What is the best way to use a HashMap in C++?
...rdered map insert and access is in O(1). It is just another name for a hashtable.
An example with (ordered) std::map:
#include <map>
#include <iostream>
#include <cassert>
int main(int argc, char **argv)
{
std::map<std::string, int> m;
m["hello"] = 23;
// check if ke...
How to check if a stored procedure exists before creating it
...ything after AS:
BEGIN
DECLARE @myvar INT
SELECT *
FROM mytable
WHERE @myvar ...
END
This code does exactly same things a stored proc would do, but is not stored on the database side.
That's much like what is called anonymous procedure in PL/SQL.
Update:
Your question tit...
UIRefreshControl - beginRefreshing not working when UITableViewController is inside UINavigationCont
I've setup a UIRefreshControl in my UITableViewController (which is inside a UINavigationController) and it works as expected (i.e. pull down fires the correct event). However, if I programmatically invoke the beginRefreshing instance method on the refresh control like:
...
Getting LaTeX into R Plots
... in the following R code: "$z\\frac{a}{b}$" -> "$\z\frac{a}{b}$\"
Also xtable exports tables to latex code
The code:
library(reshape2)
library(plyr)
library(ggplot2)
library(systemfit)
library(xtable)
require(graphics)
require(tikzDevice)
setwd("~/DataFolder/")
Lab5p9 <- read.csv (file="~/...
Scala: What is a TypeTag and how do I use it?
...flect.ClassTag[List[Int]] =↩
ClassTag[class scala.collection.immutable.List]
As one can see above, they don't care about type erasure, therefore if one wants "full" types TypeTag should be used:
scala> typeTag[List[Int]]
res105: reflect.runtime.universe.TypeTag[List[Int]] = TypeTag[s...
Add a reference column migration in Rails 4
A user has many uploads. I want to add a column to the uploads table that references the user . What should the migration look like?
...
What, exactly, is needed for “margin: 0 auto;” to work?
...y head:
The element must be block-level, e.g. display: block or display: table
The element must not float
The element must not have a fixed or absolute position1
Off the top of other people's heads:
The element must have a width that is not auto2
Note that all of these conditions must be tru...
Practical uses of different data structures [closed]
...ound the list in a similar question, previously on StackOverflow:
Hash Table - used for fast data lookup - symbol table for compilers,
database indexing, caches,Unique data representation.
Trie - dictionary, such as one found on a mobile telephone for
autocompletion and spell-checking.
...