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MySQL Multiple Joins in one query?
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I shared my experience of using two LEFT JOINS in a single SQL query.
I have 3 tables:
Table 1) Patient consists columns PatientID, PatientName
Table 2) Appointment consists columns AppointmentID, AppointmentDateTime, PatientID, DoctorID
Table 3) Doctor consists columns DoctorID,...
MediaNotification 媒体通知扩展：管理媒体播放器通知，支持播放控制 · Ap...
...,艺术家,专辑图像,持续时间)
设置扩展的媒体元数据，包括持续时间（用于进度条）。
从MediaHelper设置元数据 SetMetaDataFromMH(媒体助手组件)
从UrsMediaHelper组件获取并设置元数据。
设置暂停状态 SetStatePaused()
设置播放器状...
ALTER TABLE without locking the table?
When doing an ALTER TABLE statement in MySQL, the whole table is read-locked (allowing concurrent reads, but prohibiting concurrent writes) for the duration of the statement. If it's a big table, INSERT or UPDATE statements could be blocked for a looooong time. Is there a way to do a "hot alter", li...
SQLite - How do you join tables from different databases?
I have an application that uses a SQLite database and everything works the way it should. I'm now in the process of adding new functionalities that require a second SQLite database, but I'm having a hard time figuring out how to join tables from the different databases.
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Django in / not in query
...ite to exact. Author.objects.filter(name__ne='Jack') will translate to the SQL: "author"."name" <> 'Jack'"
from django.db.models import Lookup
class NotEqual(Lookup):
lookup_name = 'ne'
def as_sql(self, compiler, connection):
lhs, lhs_params = self.process_lhs(compiler, conn...
How to find gaps in sequential numbering in mysql?
...ve, syntax can be generated for other programming languages. Or maybe even SQL.
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string.ToLower() and string.ToLowerInvariant()
... in Turkey.
=Using ToLower incorrectly=
Now pretend you are writing an SQL parser. Somewhere you will have code that looks like:
if(operator.ToLower() == "like")
{
// Handle an SQL LIKE operator
}
The SQL grammar does not change when you change cultures. A Frenchman does not write SÉLECT...
Compare two data.frames to find the rows in data.frame 1 that are not present in data.frame 2
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SQLDF provides a nice solution
a1 <- data.frame(a = 1:5, b=letters[1:5])
a2 <- data.frame(a = 1:3, b=letters[1:3])
require(sqldf)
a1NotIna2 <- sqldf('SELECT * FROM a1 EXCEPT SELECT * FROM a2')
And the rows which...
PHP - Modify current object in foreach loop
...logic.
For retrieving objects by ID / PK, depending upon if you are using SQL or not (it seems suggested), I'd use a filter to ensure I get an array of valid PK's, then implode with comma and place into an SQL IN() clause to return the result-set. It makes one call instead of several via SQL, optim...
Are GUID collisions possible?
I'm working on a database in SQL Server 2000 that uses a GUID for each user that uses the app it's tied to. Somehow, two users ended up with the same GUID. I know that microsoft uses an algorithm to generate a random GUID that has an extremely low chance of causing collisons, but is a collision stil...