大约有 40,000 项符合查询结果（耗时：0.0285秒） [XML]
MySQL - why not index every field?
...k about index updates were one update trigger all indexes update this is a select all unordered equivalent in time
from this I conclude that you have in this scenario that if you will loose this time is preferable to lose it in a select nor an update because if you will select a field that is not i...
LINQ to SQL: Multiple joins ON multiple Columns. Is this possible?
... from child in context.Childs
where child.Parent.col2 == 4
select new
{
childCol1 = child.col1,
parentCol1 = child.Parent.col1,
};
will generate the query
SELECT [t0].[col1] AS [childCol1], [t1].[col1] AS [parentCol1]
FROM [dbo].[Child] AS [...
What's the difference between TRUNCATE and DELETE in SQL
...tranTest | DELETE FROM tranTest |
| SELECT * FROM tranTest | SELECT * FROM tranTest |
| ROLLBACK | ROLLBACK |
| SELECT * FROM tranTest | SELE...
Using TortoiseSVN via the command line
...ssociated with it. But on the installer (of version 1.7 and later) you can select the "command line client tools" option so you can call svn commands (like svn commit and svn update) from the command line.
Here's a screenshot of the "command line client tools" option in the installer, you need to m...
How to round an average to 2 decimal places in PostgreSQL?
... round that takes a precision is only available for numeric.
regress=> SELECT round( float8 '3.1415927', 2 );
ERROR: function round(double precision, integer) does not exist
regress=> \df *round*
List of functions
Schema | Name | Result data type | Argument...
Disable XML validation in Eclipse
...ngs (disable the validation for this project): Right-click on the project, select Properties > Validation and uncheck the manual and build for: XML Schema Validator, XML Validator
Right-click on the project and select Validate to make the errors disappear.
...
Check if value is in select list with JQuery
...
Use the Attribute Equals Selector
var thevalue = 'foo';
var exists = 0 != $('#select-box option[value='+thevalue+']').length;
If the option's value was set via Javascript, that will not work. In this case we can do the following:
var exists = fal...
Does order of where clauses matter in SQL?
...rstName) (or both)
On the other hand - again for SQL Server - if you use SELECT * to grab all columns from a table, and the table is rather small, then there's a good chance the query optimizer will just do a table (or clustered index) scan instead of using an index (because the lookup into the fu...
What is SQL injection? [duplicate]
...ue for any language), which might be used to handle a user login.
$sql = "SELECT FROM users WHERE username='".$_GET['username']."' AND password='".$_GET['password']."'";
The harm is done when the user enters something like
administrator'; --
... for the username. Without proper encoding the...
Renew Provisioning Profile
...gn).
I discovered that if I change something on the screen (in my case, I selected a previously
unused device), "Submit" darkens (becomes available).
Click on "Submit".
You're quietly (another UI problem :) taken back to the prior page, and the
"Download" and "Edit" buttons are gone, and the status...