大约有 5,881 项符合查询结果（耗时：0.0208秒） [XML]
How does virtual inheritance solve the “diamond” (multiple inheritance) ambiguity?
... be only 1 instance of the base A class not 2.
Your type D would have 2 vtable pointers (you can see them in the first diagram), one for B and one for C who virtually inherit A. D's object size is increased because it stores 2 pointers now; however there is only one A now.
So B::A and C::A are...
JPA EntityManager: Why use persist() over merge()?
...nate Session (a.k.a Persistence Context) and is not mapped to any database table row is considered to be in the New (Transient) state.
To become persisted we need to either explicitly call the EntityManager#persist method or make use of the transitive persistence mechanism.
Persistent (Managed)
A...
How do I use LINQ Contains(string[]) instead of Contains(string)
...ids = arrayofuids.Select(id => int.Parse(id)).ToList();
var selected = table.Where(t => uids.Contains(t.uid));
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Use a LIKE statement on SQL Server XML Datatype
If you have a varchar field you can easily do SELECT * FROM TABLE WHERE ColumnA LIKE '%Test%' to see if that column contains a certain string.
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What's the difference between VARCHAR and CHAR?
...: when Anon. says "your content is a fixed size" it means the rows of your table must contain all fixed size fields. You get no performance improvement if you use CHAR against VARCHAR in one field, but the table contains other fields that are VARCHAR.
– Marco Demaio
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Swipe to Delete and the “More” button (like in Mail app on iOS 7)
How to create a "more" button when user swipe a cell in table view (like mail app in ios 7)
20 Answers
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Query for array elements inside JSON type
... json type in PostgreSQL 9.3.
I have a json column called data in a table called reports . The JSON looks something like this:
...
What MySQL data type should be used for Latitude/Longitude with 8 decimal places?
...types and Point is a single-value type which can be used. Example:
CREATE TABLE `buildings` (
`coordinate` POINT NOT NULL,
/* Even from v5.7.5 you can define an index for it */
SPATIAL INDEX `SPATIAL` (`coordinate`)
) ENGINE=InnoDB;
/* then for insertion you can */
INSERT INTO `buildings`
(...
Command line CSV viewer? [closed]
...ropriate width of each column, and displays the text as a nicely formatted table.
Note: whenever you have empty fields, you need to put some kind of placeholder in it, otherwise the column gets merged with following columns. The following example demonstrates how to use sed to insert a placeholder:...
Add a custom attribute to a Laravel / Eloquent model on load?
...s any accessors which do not directly relate to a column in the underlying table.
As Taylor Otwell mentioned here, "This is intentional and for performance reasons." However there is an easy way to achieve this:
class EventSession extends Eloquent {
protected $table = 'sessions';
protecte...