大约有 37,000 项符合查询结果（耗时：0.0293秒） [XML]
What is a NullReferenceException, and how do I fix it?
...that C# has the concept of nullable datatypes for variables (like database tables can have nullable fields) - you can assign null to them to indicate there is no value stored in it, for example int? a = null; where the question mark indicates it is allowed to store null in variable a. You can check ...
Why is SSE scalar sqrt(x) slower than rsqrt(x) * x?
... there are some info, especially about rsqrt (cpu is using internal lookup table with huge approximation, which makes it much simpler to get the result). It may seem, that rsqrt is so much faster than sqrt, that 1 additional mul operation (which isn't to costly) might not change the situation here. ...
Doctrine2: Best way to handle many-to-many with extra columns in reference table
...port AppBundle yml still generate manyToMany relation for the original two tables and simply ignore the third table instead of concidering it as an entity :/
– Stphane
Mar 18 '15 at 23:24
...
How to remove not null constraint in sql server using query
...
ALTER TABLE YourTable ALTER COLUMN YourColumn columnType NULL
share
|
improve this answer
|
follow
...
How to add not null constraint to existing column in MySQL
I have table name called "Person" with following column names
2 Answers
2
...
记一次数据库表自增长（Auto Increment）故障 - 数据库(内核) - 清泛网 - ...
...主键值。
我们不妨创建一个测试表说明问题：
CREATE TABLE IF NOT EXISTS `test` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(100) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB;
然后插入一行问题数据：
INSERT INTO test (id, name) VALUES (2147483647...
Hibernate throws org.hibernate.AnnotationException: No identifier specified for entity: com..domain.
...he database.
If you don't want your entity to be persisted in a separate table, but rather be a part of other entities, you can use @Embeddable instead of @Entity.
If you want simply a data transfer object to hold some data from the hibernate entity, use no annotations on it whatsoever - leave it...
How do I bottom-align grid elements in bootstrap fluid layout
...
This is the only acceptable answer! @Lukas's will ignore widths on columns that don't fill a row. And DOM manipulation for styling... SMH.
– Archonic
May 30 '15 at 3:59
...
Is there a version control system for database structure changes?
...the version (such as removing a column). Each migration is numbered, and a table keeps track of your current db version.
To migrate up, you run a command called "db:migrate" which looks at your version and applies the needed scripts. You can migrate down in a similar way.
The migration scripts the...
How to select multiple rows filled with constants?
Selecting constants without referring to a table is perfectly legal in an SQL statement:
15 Answers
...