大约有 37,000 项符合查询结果（耗时：0.0365秒） [XML]
SQL Server 2005 How Create a Unique Constraint?
How do I create a unique constraint on an existing table in SQL Server 2005?
10 Answers
...
Can I create a named default constraint in an add column statement in SQL Server?
In SQL Server, I have a new column on a table:
4 Answers
4
...
How to implement the activity stream in a social network
...rowse far back in time (if you even offer this)
I use a plain old MySQL table for dealing with about 15 million activities.
It looks something like this:
id
user_id (int)
activity_type (tinyint)
source_id (int)
parent_id (int)
parent_type (tinyint)
time (...
What are the disadvantages of using persistent connection in PDO
...tion die when the script terminates abnormally.
If the dead script locked tables, those tables will remain locked until the connection dies or the next script that gets the connection unlocks the tables itself.
If the dead script was in the middle of a transaction, that can block a multitude of ta...
Why do we always prefer using parameters in SQL statements?
...ommands against your database, including deleting it If they wrote 0; Drop Table employee:
SELECT empSalary from employee where salary = 0; Drop Table employee
The table employee would then be deleted.
In your case, it looks like you're using .NET. Using parameters is as easy as:
C#
string s...
What is the optimal length for user password salt? [closed]
...ices for how long the salt should be? I'll be storing the salt in my user table, so I would like the best tradeoff between storage size and security. Is a random 10 character salt enough? Or do I need something longer?
...
How to get cumulative sum
...
@Franklin Only cost efficient for small tables. Cost grows proportional to the square of the number of rows. SQL Server 2012 allows this to be done much more efficiently.
– Martin Smith
May 18 '13 at 19:57
...
MYSQL Dump only certain rows
...t dumps everything. How can I get mysqldump to only dump certain rows of a table?
3 Answers
...
What is the most ridiculous pessimization you've seen? [closed]
...
Databases are pessimization playland.
Favorites include:
Split a table into multiples (by date range, alphabetic range, etc.) because it's "too big".
Create an archive table for retired records, but continue to UNION it with the production table.
Duplicate entire databases by (division/cus...
What are file descriptors, explained in simple terms?
...file in operating system.
If your process opens 10 files then your Process table will have 10 entries for file descriptors.
Similarly when you open a network socket, it is also represented by an integer and it is called Socket Descriptor.
I hope you understand.
...