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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,...
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...
周鸿祎创业以来的“六大战役” 酷派会是最后一战 - 资讯 - 清泛网 - 专注C/...
...软件动摇了杀毒行业盈利根本，得罪了不少同行，其中还包括雷军和马化腾。
第三战：养虎为患傅盛出走
说到傅盛，不得不提他与周鸿祎的那段师徒史，傅盛的成功多少是周鸿祎给的，傅盛的年少自大，导致了最终一拍两散...
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...