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Does MySQL index foreign key columns automatically?
Does MySQL index foreign key columns automatically?
9 Answers
9
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How to round up to the nearest 10 (or 100 or X)?
...en just define:
roundUp <- function(x) 10^ceiling(log10(x))
This actually also works when x is a vector:
> roundUp(c(0.0023, 3.99, 10, 1003))
[1] 1e-02 1e+01 1e+01 1e+04
..but if you want to round to a "nice" number, you first need to define what a "nice" number is. The following lets us...
How expensive is the lock statement?
I've been experimenting with multi threading and parallel processing and I needed a counter to do some basic counting and statistic analysis of the speed of the processing. To avoid problems with concurrent use of my class I've used a lock statement on a private variable in my class:
...
How to print HTML content on click of a button, but not the page? [duplicate]
...intDiv('printableArea')" value="print a div!" />
Now let's create a really simple javascript:
function printDiv(divName) {
var printContents = document.getElementById(divName).innerHTML;
var originalContents = document.body.innerHTML;
document.body.innerHTML = printContents;
...
Parsing CSV files in C#, with header
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Let a library handle all the nitty-gritty details for you! :-)
Check out FileHelpers and stay DRY - Don't Repeat Yourself - no need to re-invent the wheel a gazillionth time....
You basically just need to define that shape of your data - the fi...
jQuery templating engines [closed]
...sRepeater and jQuery Templates. While they seem to work OK in FireFox they all seem to break down in IE7 when it comes down to rendering HTML tables.
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Can we have functions inside functions in C++?
...rm of a lambda:
int main() {
// This declares a lambda, which can be called just like a function
auto print_message = [](std::string message)
{
std::cout << message << "\n";
};
// Prints "Hello!" 10 times
for(int i = 0; i < 10; i++) {
print...
What is the difference among col-lg-*, col-md-* and col-sm-* in Bootstrap?
...a new -xl- size, see this demo. Also the -xs- infix has been removed, so smallest columns are simply col-1, col-2.. col-12, etc..
col-* - 0 (xs)
col-sm-* - 576px
col-md-* - 768px
col-lg-* - 992px
col-xl-* - 1200px
Bootstrap 4 Grid Demo
Additionally, Bootstrap 4 includes new auto-layout columns. Thes...
Can a foreign key be NULL and/or duplicate?
...at field must exist first in a different table (the parent table). That is all an FK is by definition. Null by definition is not a value. Null means that we do not yet know what the value is.
Let me give you a real life example. Suppose you have a database that stores sales proposals. Suppose furth...
DISTINCT for only one column
... needs a WHERE condition. I'm thinking the row numbers will be assigned to all rows in the table. This syntax is just a little beyond me. Any chance of an update that would guarantee one row with a particular email that meets the WHERE condition?
– Jonathan Wood
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