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MongoDB relationships: embed or reference?
...y you much) there is no immediate need to normalize data like you would in SQL. In particular any data that is not useful apart from its parent document should be part of the same document.
Separate data that can be referred to from multiple places into its own collection.
This is not so much a "s...
How to find the size of an array in postgresql
...w that the array is 1-dimensional (which is likely) and are running PostgreSQL 9.4 or higher, you can use cardinality:
SELECT cardinality(id) FROM example;
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How to test Spring Data repositories?
...serting object instances through the EntityManager or repo, or via a plain SQL file) and then execute the query methods to verify the outcome of them.
Testing custom implementations
Custom implementation parts of the repository are written in a way that they don't have to know about Spring Data JP...
How to select bottom most rows?
...ere n is the count; x <= n
E.g. Select Bottom 1000 from Employee:
In T-SQL,
DECLARE
@bottom int,
@count int
SET @bottom = 1000
SET @count = (select COUNT(*) from Employee)
select * from Employee emp where emp.EmployeeID not in
(
SELECT TOP (@count-@bottom) Employee.EmployeeID FROM Employee
...
How does Amazon RDS backup/snapshot actually work?
...
We also run several RDS instances, in addition to MySQL on some machines that we manage ourselves. I can't comment specifically, as I'm not an Amazon engineer, but several things I've learned that might explain what you're seeing:
Although Amazon does not share the backend d...
Can someone explain mappedBy in JPA and Hibernate?
...not something you usually want to do and can cause problems with the order SQL statements are executed.
– Affe
Feb 2 '12 at 7:51
...
What is copy-on-write?
...used in maintenance of instant snapshot on database servers like Microsoft SQL Server 2005. Instant snapshots preserve a static view of a database by storing a pre-modification copy of data when underlaying data are updated. Instant snapshots are used for testing uses or moment-dependent reports and...
Rails 3 datatypes?
...these types to the database types, too:
For, example, note that in MS SQL Server we are using:
the old "datetime" instead "datetime2"
decimal with its default precision
text and varchar instead nvarchar
int (not possible to use tiny int/small int/big int)
image instead BLOB
...
Creating a DateTime in a specific Time Zone in c#
...
I don't know of any equivalent SQL Server construct, I'm afraid. I would suggest having the time zone name as one column, and the UTC value in another column. Fetch them separately and then you can create instances fairly easily.
– Jo...
Is there a “null coalescing” operator in JavaScript?
...ed, xyz.val, 5);
// xyz.val now contains 5
this solution works like the SQL coalesce function, it accepts any number of arguments, and returns null if none of them have a value. It behaves like the C# ?? operator in the sense that "", false, and 0 are considered NOT NULL and therefore count as a...