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The type 'string' must be a non-nullable type in order to use it as parameter T in the generic type
Why do I get Error "The type 'string' must be a non-nullable value type in order to use it as parameter 'T' in the generic type or method 'System.Nullable'"?
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select * vs select column
...as to what you want, it will first need to check the table's definition in order to determine the columns on that table. That lookup will cost some time - not much in a single query - but it adds up over time
if you need only 2/3 of the columns, you're selecting 1/3 too much data which needs to be r...
Why JSF calls getters multiple times
...public Boolean getGmapsAutoComplete() {
switch (page) {
case "/orders/pf_Add.xhtml":
case "/orders/pf_Edit.xhtml":
case "/orders/pf_EditDriverVehicles.xhtml":
gmapsAutoComplete = true;
break;
default:
gmapsAutoComplete = false;
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When and why are database joins expensive?
... bulk disk reads which are the most expensive aspect of the exercise by an order of magnitude. Performing a join, by contrast, logically requires retrieval of only the keys. In practice, not even the key values are fetched: the key hash values are used for join comparisons, mitigating the cost of mu...
View's SELECT contains a subquery in the FROM clause
...y client_id
create view view_credit_status as
select
credit_orders.client_id,
sum(credit_orders.number_of_credits) as purchased,
ifnull(t1.credits_used,0) as used
from credit_orders
left outer join view_clients_credit_usage as t1 on t1.client_id = credit_ord...
How to get all possible combinations of a list’s elements?
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the input iterable.
Combinations are emitted in lexicographic sort order. So, if the
input iterable is sorted, the
combination tuples will be produced in
sorted order.
Since 2.6, batteries are included!
share...
Is recursion ever faster than looping?
...the best alternative is neither recursion nor iteration but instead higher order functions. These include "map", "filter", and "reduce" (which is also called "fold"). Not only are these the preferred style, not only are they often cleaner, but in some environments these functions are the first (or...
Best way to work with dates in Android SQLite [closed]
...x));
}
can be used like this:
entity.setDate(loadDate(cursor, INDEX));
Ordering by date is simple SQL ORDER clause (because we have a numeric column). The following will order descending (that is newest date goes first):
public static final String QUERY = "SELECT table._id, table.dateCol FROM t...
Unioning two tables with different number of columns
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I came here and followed above answer. But mismatch in the Order of data type caused an error. The below description from another answer will come handy.
Are the results above the same as the sequence of columns in your table? because oracle is strict in column orders. this example ...
Get the latest record from mongodb collection
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So, what's the difference with this order : db.collection.find().sort({$natural:-1}).limit(1).pretty()
– Leo
Nov 2 '16 at 2:32
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