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Is a Python dictionary an example of a hash table?
...looking up "values" of any type. Is this implemented internally as a hash table? If not, what is it?
4 Answers
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Adding multiple columns AFTER a specific column in MySQL
I need to add multiple columns to a table but position the columns after a column called lastname .
10 Answers
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Meaning of Open hashing and Closed hashing
... us the index (aka. address) at which an object will be stored in the hash table is not completely determined by its hash code. Instead, the index may vary depending on what's already in the hash table.
The "closed" in "closed hashing" refers to the fact that we never leave the hash table; every...
Querying DynamoDB by date
...ndary indexes can either be global, meaning that the index spans the whole table across hash keys, or local meaning that the index would exist within each hash key partition, thus requiring the hash key to also be specified when making the query.
For the use case in this question, you would want to...
Difference between EXISTS and IN in SQL?
... as a way to avoid counting:
--this statement needs to check the entire table
select count(*) from [table] where ...
--this statement is true as soon as one match is found
exists ( select * from [table] where ... )
This is most useful where you have if conditional statements, as exists can be ...
What is the error “Every derived table must have its own alias” in MySQL?
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Every derived table (AKA sub-query) must indeed have an alias. I.e. each query in brackets must be given an alias (AS whatever), which can the be used to refer to it in the rest of the outer query.
SELECT ID FROM (
SELECT ID, msisdn F...
MySQL Update Inner Join tables query
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Update:
Since you said the query yielded a syntax error, I created some tables that I could test it against and confirmed that there is no syntax error in my query:
mysql> create table business (business_id int unsigned primary key auto_increment, mapx varchar(255), mapy varchar(255)) engine=...
How do I update a Linq to SQL dbml file?
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There are three ways to keep the model in sync.
Delete the modified tables from the designer, and drag them back onto the designer surface from the Database Explorer. I have found that, for this to work reliably, you have to:
a. Refresh the database schema in the Database Explorer (right-c...
PostgreSQL: Can you create an index in the CREATE TABLE definition?
I want to add indexes to some of the columns in a table on creation. Is there are way to add them to the CREATE TABLE definition or do I have to add them afterward with another query?
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How to get multiple counts with one SQL query?
...(case when level = 'personal' then 1 else 0 end) AS PersonalCount
FROM yourtable
GROUP BY distributor_id
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