大约有 9,000 项符合查询结果（耗时：0.0377秒） [XML]
Why is there a difference in checking null against a value in VB.NET and C#?
...ditional advantage of mirroring the behaviour of NULL in (most if not all) SQL databases. This is also a more standard (than C#'s) interpretation of three-valued logic, as explained here.
The C# team made different assumptions about what NULL means, resulting in the behaviour difference you show. E...
How do I free my port 80 on localhost Windows?
...t 80 in windows.
IIS
World Wide Web Publishing service
IIS Admin Service
SQL Server Reporting services
Web Deployment Agent Service
Stop above applications if running and check!!!
share
|
impro...
JOIN queries vs multiple queries
...ou are joining 3 or more tables on different keys, often databases (i.e. mysql) can only use one index per table, meaning maybe one of the joins will be fast (and use an index) whereas the others will be extremely slow. For multiple queries, you can optimize the indexes to use for each query.
...
Saving timestamp in mysql table using php
I have a field in a MySQL table which has a timestamp data type. I am saving data into that table. But when I pass the timestamp ( 1299762201428 ) to the record, it automatically saves the value 0000-00-00 00:00:00 into that table.
...
Difference between Destroy and Delete
...sted). Returns the frozen instance.
The row is simply removed with an SQL DELETE statement on the record's primary key, and no callbacks are executed.
To enforce the object's before_destroy and after_destroy callbacks or any :dependent association options, use #destroy.
ActiveRecord::Pers...
Storing DateTime (UTC) vs. storing DateTimeOffset
...
Not the answer you're looking for? Browse other questions tagged sql sql-server tsql sql-server-2008 datetimeoffset or ask your own question.
Convert timestamp to date in MySQL query
I want to convert a timestamp in MySQL to a date.
10 Answers
10
...
Add Foreign Key to existing table
...n "SET FOREIGN_KEY_CHECKS=0;" before running the ADD CONSTRAINT command or SQL would complain "Cannot add or update a child row: a foreign key constraint fails".
– Erin Geyer
Mar 8 '17 at 13:03
...
Modify table: How to change 'Allow Nulls' attribute from not null to allow null
How to change one attribute in a table using T-SQL to allow nulls (not null --> null)? Alter table maybe?
8 Answers
...
NHibernate.MappingException: No persister for: XYZ
...guration..
If you're using app.config...
.
.
<property name="show_sql">true</property>
<property name="query.substitutions">true 1, false 0, yes 'Y', no 'N'</property>
<mapping assembly="Project.DomainModel"/> <!-- Here -->
</session-factory>
...