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Does MySQL ignore null values on unique constraints?
...ws multiple NULLs in a column with a unique constraint.
CREATE TABLE table1 (x INT NULL UNIQUE);
INSERT table1 VALUES (1);
INSERT table1 VALUES (1); -- Duplicate entry '1' for key 'x'
INSERT table1 VALUES (NULL);
INSERT table1 VALUES (NULL);
SELECT * FROM table1;
Result:
x
NULL
NULL
1
This i...
Check if my app has a new version on AppStore
...
91
Here is a simple code snippet that lets you know if the current version is different
-(BOOL) ne...
select and update database record with a single queryset
...et object update method:
MyModel.objects.filter(pk=some_value).update(field1='some value')
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How do I return multiple values from a function? [closed]
...
14 Answers
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Avoid duplicates in INSERT INTO SELECT query in SQL Server
...
Using NOT EXISTS:
INSERT INTO TABLE_2
(id, name)
SELECT t1.id,
t1.name
FROM TABLE_1 t1
WHERE NOT EXISTS(SELECT id
FROM TABLE_2 t2
WHERE t2.id = t1.id)
Using NOT IN:
INSERT INTO TABLE_2
(id, name)
SELECT t1.id,
t1.name
F...
Why is i++ not atomic?
...
125
i++ is probably not atomic in Java because atomicity is a special requirement which is not pre...
How to get the last date of a particular month with JodaTime?
... |
edited Jun 20 at 9:12
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answered Mar 14 '12 at 22:47
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Cluster analysis in R: determine the optimal number of clusters
...
1024
If your question is how can I determine how many clusters are appropriate for a kmeans analys...
Measure execution time for a Java method [duplicate]
...em.out.println(stopTime - startTime);
In Java 8 (output format is ISO-8601):
Instant start = Instant.now();
Thread.sleep(63553);
Instant end = Instant.now();
System.out.println(Duration.between(start, end)); // prints PT1M3.553S
Guava Stopwatch:
Stopwatch stopwatch = Stopwatch.createStarted()...