大约有 6,100 项符合查询结果（耗时：0.0298秒） [XML]
When/Why to use Cascading in SQL Server?
...eal key rather than a surrogate key (identity/autoincrement column) across tables.
The canonical example for Cascade Update is when you have a mutable foreign key, like a username that can be changed.
You should not use Cascade Update with keys that are Identity/autoincrement columns.
Cascade Updat...
How do I horizontally center a span element inside a div
...
another option would be to give the span display:table; and center it via margin:0 auto;
span {
display:table;
margin:0 auto;
}
share
|
improve this answer
|
...
What does the “@” symbol do in Powershell?
...l V2, @ is also the Splat operator.
PS> # First use it to create a hashtable of parameters:
PS> $params = @{path = "c:\temp"; Recurse= $true}
PS> # Then use it to SPLAT the parameters - which is to say to expand a hash table
PS> # into a set of command line parameters.
PS> dir @para...
How to check if a database exists in SQL Server?
...ing the INFORMATION_SCHEMA views rather than directly accessing the system tables.
– mwigdahl
Mar 24 '09 at 20:09
4
...
How to define a custom ORDER BY order in mySQL
...age,'ENU','JPN','DAN'), ID
Note however, that
It makes your SQL less portable, as other DBMSs might not have such function
When your list of languages (or other values to sort by) gets much longer, it's better to have a separate table with sortorder column for them, and join it to your queries fo...
SQL select only rows with max value on a column [duplicate]
I have this table for documents (simplified version here):
27 Answers
27
...
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...
How to test an SQL Update statement before running it?
...man/5.0/en/commit.html
For example:
START TRANSACTION;
SELECT * FROM nicetable WHERE somthing=1;
UPDATE nicetable SET nicefield='VALUE' WHERE somthing=1;
SELECT * FROM nicetable WHERE somthing=1; #check
COMMIT;
# or if you want to reset changes
ROLLBACK;
SELECT * FROM nicetable WHERE somthing=1...
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...
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.
...