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How to check if a variable is set in Bash?
... This answer is very confusing. Any practical examples on how to use this table?
– Ben Davis
Sep 27 '14 at 17:16
13
...
Rails 3 migrations: Adding reference column?
...class AddUserToTester < ActiveRecord::Migration
def change
change_table :testers do |t|
t.references :user, index: true
end
end
def down
change_table :testers do |t|
t.remove :user_id
end
end
end
c.f.: http://apidock.com/rails/ActiveRecord/ConnectionAdapters...
Java: parse int value from a char
...ou take '2' - '0' you really just get 50 - 48 = 2. Have a look at an ASCII table in order to understand this principle better. Also, 'x' means get the ascii value of the character in Java.
– Kevin Van Ryckegem
May 13 '17 at 13:16
...
Versioning SQL Server database
...N to N+1. (These go in your version control system.) A _version_history_ table, something like
create table VersionHistory (
Version int primary key,
UpgradeStart datetime not null,
UpgradeEnd datetime
);
gets a new entry every time an upgrade script runs which corresponds to th...
How can I read and parse CSV files in C++?
...::istream &in) {
std::vector<std::vector<std::string>> table;
std::string row;
while (!in.eof()) {
std::getline(in, row);
if (in.bad() || in.fail()) {
break;
}
auto fields = readCSVRow(row);
table.push_back(fields);
...
ActiveRecord: size vs count
...e way to go if you are using the data.
Example: Summary of a fully loaded table, titles of displayed data, etc.
size
It checks if the data was loaded (i.e. already in rails) if so, then just count it, otherwise it calls count. (plus the pitfalls, already mentioned in other entries).
def size
l...
How to return an empty ActiveRecord relation?
...
A more portable solution that doesn't require an "id" column and doesn't assume there won't be a row with an id of 0:
scope :none, where("1 = 0")
I'm still looking for a more "correct" way.
...
Create new user in MySQL and give it full access to one database
... - This is the command used to create users and grant rights to databases, tables, etc.
ALL PRIVILEGES - This tells it the user will have all standard privileges. This does not include the privilege to use the GRANT command however.
dbtest.* - This instructions MySQL to apply these rights for use ...
What is the best way to solve an Objective-C namespace collision?
...not changing the address of the original symbol. Objective-C uses a lookup table to map class names to addresses, and it's a 1-1 mapping, so you can't have two classes with the same name. Thus, to load both classes, one of them must have their name changed. However, when other classes need to access...
LEFT OUTER joins in Rails 3
... the :include option, which will perform an
INNER JOIN on the associated table(s), or an array containing a
mixture of both strings and named associations.
If the value is a
string, then the records will be returned read-only since they will
have attributes that do not correspond to th...