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SQL: How to properly check if a record exists
...E unique_key = value;
The first alternative should give you no result or one result, the second count should be zero or one.
How old is the documentation you're using? Although you've read good advice, most query optimizers in recent RDBMS's optimize SELECT COUNT(*) anyway, so while there is a di...
Are duplicate keys allowed in the definition of binary search trees?
...airly trivial to implement duplicates (either as a list at the node, or in one particular direction.)
Most (that I've seen) specify left children as <= and right children as >. Practically speaking, a BST which allows either of the right or left children to be equal to the root node, will re...
One-liner to take some properties from object in ES 6
How one can write a function, which takes only few attributes in most-compact way in ES6?
11 Answers
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How can I rename a database column in a Ruby on Rails migration?
...a column, Rails 4 generates a change method instead of up and down as mentioned in the above section. The generated change method is:
$ > rails g migration ChangeColumnName
which will create a migration file similar to:
class ChangeColumnName < ActiveRecord::Migration
def change
ren...
How to pull a random record using Django's ORM?
...ent on my site. On the main webpage I'd like to show some of them: newest, one that was not visited for most time, most popular one and a random one.
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Signed to unsigned conversion in C - is it always safe?
...e type of the operand with signed integer type.
In your case, we have one unsigned int (u) and signed int (i). Referring to (3) above, since both operands have the same rank, your i will need to be converted to an unsigned integer.
6.3.1.3 Signed and unsigned integers
When a value w...
Is it possible to change a UIButtons background color?
This one has me stumped.
16 Answers
16
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T-SQL: Deleting all duplicate rows but keeping one [duplicate]
...lightly different data but I do not care about that. I still need to keep one of these rows however. SELECT DISTINCT won't work because it operates on all columns and I need to suppress duplicates based on the key columns.
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Are GUID collisions possible?
...
Basically, no. I think someone went mucking with your database. Depending on the version GUID you're using the value is either unique (for things like version 1 GUIDs), or both unique and unpredictable (for things like version 4 GUIDs). SQL Server's ...
How to check in Javascript if one element is contained within another
How can I check if one DOM element is a child of another DOM element? Are there any built in methods for this? For example, something like:
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