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add column to mysql table if it does not exist
... MySQL prior to 5.0. Nor are stored procedures supported prior to 5.0, so if you need to support MySQL 4.1, this solution isn't good.
One solution used by frameworks that use database migrations is to record in your database a revision number for the schema. Just a table with a single column and ...
Difference between if () { } and if () : endif;
Are there any differences between...
18 Answers
18
...
Using parameters in batch files at Windows command line
...r tokens that you can use:
%0 is the executable (batch file) name as specified in the command line.
%* is all parameters specified in the command line -- this is very useful if you want to forward the parameters to another program.
There are also lots of important techniques to be aware of in ad...
Does Go have “if x in” construct similar to Python?
Without iterating over the entire array, how can I check if x in array using Go? Does the language have a construct?
7 A...
What is the purpose of “&&” in a shell command?
...wo
the intent is to execute the command that follows the && only if the first command is successful. This is idiomatic of Posix shells, and not only found in Bash.
It intends to prevent the running of the second process if the first fails.
You may notice I've used the word "intent" - tha...
Compare two objects' properties to find differences?
...s tricky.
public bool ReflectiveEquals(object first, object second)
{
if (first == null && second == null)
{
return true;
}
if (first == null || second == null)
{
return false;
}
Type firstType = first.GetType();
if (second.GetType() != firstT...
How can I convert String to Int?
...e to make decisions about the results of the parsing attempt:
int x = 0;
if (Int32.TryParse(TextBoxD1.Text, out x))
{
// you know that the parsing attempt
// was successful
}
If you are curious, the difference between Parse and TryParse is best summed up like this:
The TryParse metho...
Check Whether a User Exists
...n also check user by id command.
id -u name gives you the id of that user.
if the user doesn't exist, you got command return value ($?)1
And as other answers pointed out: if all you want is just to check if the user exists, use if with id directly, as if already checks for the exit code. There's no ...
Check if application is on its first run [duplicate]
...verride
protected void onResume() {
super.onResume();
if (prefs.getBoolean("firstrun", true)) {
// Do first run stuff here then set 'firstrun' as false
// using the following line to edit/commit prefs
prefs.edit().putBoolean("firstrun", false)...
Get the first item from an iterable that matches a condition
...
In Python 2.6 or newer:
If you want StopIteration to be raised if no matching element is found:
next(x for x in the_iterable if x > 3)
If you want default_value (e.g. None) to be returned instead:
next((x for x in the_iterable if x > 3), d...