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SQL “select where not in subquery” returns no results
...L:
SELECT *
FROM common
LEFT JOIN
table1 t1
ON t1.common_id = common.common_id
WHERE t1.common_id IS NULL
NOT EXISTS:
SELECT *
FROM common
WHERE NOT EXISTS
(
SELECT NULL
FROM table1 t1
WHERE t1.common_id = common.common_id
)
...
Distributed sequence number generation?
...ing now.
You'll need to differentiate between sequence numbers and unique IDs that are (optionally) loosely sortable by a specific criteria (typically generation time). True sequence numbers imply knowledge of what all other workers have done, and as such require shared state. There is no easy way ...
How to select a single field for all documents in a MongoDB collection?
...ery. In the result set, only the item and qty fields and, by default, the _id field return in the matching documents.
db.inventory.find( { type: 'food' }, { item: 1, qty: 1 } )
In this example from the folks at Mongo, the returned documents will contain only the fields of item, qty, and _id.
Thus,...
SQL JOIN and different types of JOINs
... @KNU The w3fools should give credit from where they have taken the idea for the pictures. See A visualization of SQL joins by Jeff Atwood (yes, the one who co-authored SO) and the linked article by Ligaya Turmelle where Jeff got the idea and explanded it.
– ypercubeᵀ...
Passing an array to a query using a WHERE clause
Given an array of ids $galleries = array(1,2,5) I want to have a SQL query that uses the values of the array in its WHERE clause like:
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Mysql error 1452 - Cannot add or update a child row: a foreign key constraint fails
...
Quite likely your sourcecodes_tags table contains sourcecode_id values that no longer exists in your sourcecodes table. You have to get rid of those first.
Here's a query that can find those IDs:
SELECT DISTINCT sourcecode_id FROM
sourcecodes_tags tags LEFT JOIN sourcecodes sc ON...
Python - List of unique dictionaries
...
So make a temporary dict with the key being the id. This filters out the duplicates.
The values() of the dict will be the list
In Python2.7
>>> L=[
... {'id':1,'name':'john', 'age':34},
... {'id':1,'name':'john', 'age':34},
... {'id':2,'name':'hanna', 'age':30},...
Would it be beneficial to begin using instancetype instead of id?
Clang adds a keyword instancetype that, as far as I can see, replaces id as a return type in -alloc and init .
4 An...
How do I add a Fragment to an Activity with a programmatically created content view
...han one problem with that code. A fragment cannot be declared that way, inside the same java file as the activity but not as a public inner class. The framework expects the fragment's constructor (with no parameters) to be public and visible. Moving the fragment into the Activity as an inner class, ...
Check if a key exists inside a json object
...bove is the JSON object I'm dealing with. I want to check if the 'merchant_id' key exists. I tried the below code, but it's not working. Any way to achieve it?
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