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Scala: What is a TypeTag and how do I use it?
...flect.ClassTag[List[Int]] =↩
ClassTag[class scala.collection.immutable.List]
As one can see above, they don't care about type erasure, therefore if one wants "full" types TypeTag should be used:
scala> typeTag[List[Int]]
res105: reflect.runtime.universe.TypeTag[List[Int]] = TypeTag[s...
SQL ON DELETE CASCADE, Which Way Does the Deletion Occur?
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Cascade will work when you delete something on table Courses. Any record on table BookCourses that has reference to table Courses will be deleted automatically.
But when you try to delete on table BookCourses only the table itself is affected and not on the Courses
foll...
B-Tree vs Hash Table
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You can only access elements by their primary key in a hashtable.
This is faster than with a tree algorithm (O(1) instead of log(n)), but you cannot select ranges (everything in between x and y).
Tree algorithms support this in Log(n) whereas hash indexes can result in a full table s...
C# switch statement limitations - why?
...a CIL switch statement which is indeed a constant time branch using a jump table. However, in sparse cases as pointed out by Ivan Hamilton the compiler may generate something else entirely.
This is actually quite easy to verify by writing various C# switch statements, some sparse, some dense, and ...
PostgreSQL wildcard LIKE for any of a list of words
...t's say that list is ['foo', 'bar', 'baz'] . I want to find any row in my table that has any of those words. This will work, but I'd like something more elegant.
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how can I Update top 100 records in sql server
I want to update the top 100 records in SQL Server. I have a table T1 with fields F1 and F2 . T1 has 200 records. I want to update the F1 field in the top 100 records. How can I update based on TOP 100 in SQL Server?
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select into in mysql
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Use the CREATE TABLE SELECT syntax.
http://dev.mysql.com/doc/refman/5.0/en/create-table-select.html
CREATE TABLE new_tbl SELECT * FROM orig_tbl;
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Count(*) vs Count(1) - SQL Server
...uld be evaluated as per ANSI
b) Otherwise, let TX be the single-column table that is the
result of applying the <value expression> to each row of T
and eliminating null values. If one or more null values are
eliminated, then a completion cond...
Auto Generate Database Diagram MySQL [closed]
... every project. Is there a tool out there that will let me select specific tables and then create a database diagram for me based on a MySQL database? Preferably it would allow me to edit the diagram afterward since none of the foreign keys are set...
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Is having an 'OR' in an INNER JOIN condition a bad idea?
... to improve the speed of an immensely slow query (several minutes on two tables with only ~50,000 rows each, on SQL Server 2008 if it matters), I narrowed down the problem to an OR in my inner join, as in:
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