大约有 47,000 项符合查询结果（耗时：0.0516秒） [XML]
MySQL: Transactions vs Locking Tables
...ransactions vs locking tables to ensure database integrity and make sure a SELECT and UPDATE remain in sync and no other connection interferes with it. I need to:
...
What is the difference between Non-Repeatable Read and Phantom Read?
...e query have the same value before and after, but different rows are being selected (because B has deleted or inserted some). Example: select sum(x) from table; will return a different result even if none of the affected rows themselves have been updated, if rows have been added or deleted.
In ...
What is a good reason to use SQL views?
...one extra column active.
If your system(s) have gazillion queries that do SELECT whatever FROM T_OLD WHERE whatever, you have two choices for the roll-out:
1) Cold Turkey - Change the DB, and at the same time, change, test and release numerous pieces of code which contained said query. VERY hard t...
Android Studio: Add jar as library?
.... Click the + sign above the panel second from the left -> Java
4.4. Select your local jar and add it to the project.
You may need to run the above ./gradlew command one more time
share
|
imp...
MySQL/SQL: Group by date only on a Datetime column
...
Cast the datetime to a date, then GROUP BY using this syntax:
SELECT SUM(foo), DATE(mydate) FROM a_table GROUP BY DATE(a_table.mydate);
Or you can GROUP BY the alias as @orlandu63 suggested:
SELECT SUM(foo), DATE(mydate) DateOnly FROM a_table GROUP BY DateOnly;
Though I don't think...
COUNT DISTINCT with CONDITIONS
...
You can try this:
select
count(distinct tag) as tag_count,
count(distinct (case when entryId > 0 then tag end)) as positive_tag_count
from
your_table_name;
The first count(distinct...) is easy.
The second one, looks somewhat complex...
Sqlite: CURRENT_TIMESTAMP is in GMT, not the timezone of the machine
...a unix
timestamp 1092941466, and compensate
for your local timezone.
SELECT datetime(1092941466, 'unixepoch', 'localtime');
That didn't look like it fit my needs, so I tried changing the "datetime" function around a bit, and wound up with this:
select datetime(timestamp, 'localtime')
That...
PowerShell script to return versions of .NET Framework on a machine?
...ame Version,Release -EA 0 |
Where { $_.PSChildName -match '^(?!S)\p{L}'} |
Select PSChildName, Version, Release
Based on the MSDN article, you could build a lookup table and return the marketing product version number for releases after 4.5:
$Lookup = @{
378389 = [version]'4.5'
378675 = [...
How to change the Eclipse default workspace?
...down>Workspaces.
There you can set a flag to make Eclipse prompt you to select a workspace at startup by checking the "Prompt for workspace at startup" checkbox.
You can set the number of previous workspaces to remember also. Finally there is a list of recent workspaces. If you just remove all b...
ReactJS Two components communicating
...te is also increasing in complexity, as we need to
manage active routes, selected tabs, spinners, pagination controls,
and so on.
Managing this ever-changing state is hard. If a model can update
another model, then a view can update a model, which updates another
model, and this, in tur...