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What's the fastest way to do a bulk insert into Postgres?
...e as CSV formatted mapping in PG query statement's. You can try for Big Table?
– Elyor
Sep 9 '14 at 2:03
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Data structure: insert, remove, contains, get random element, all at O(1)
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Consider a data structure composed of a hashtable H and an array A. The hashtable keys are the elements in the data structure, and the values are their positions in the array.
insert(value): append the value to array and let i be its index in A. Set H[value]=i.
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Sorting arrays in NumPy by column
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You can sort on multiple columns as per Steve Tjoa's method by using a stable sort like mergesort and sorting the indices from the least significant to the most significant columns:
a = a[a[:,2].argsort()] # First sort doesn't need to be stable.
a = a[a[:,1].argsort(kind='mergesort')]
a = a[a[:,...
SQL to find the number of distinct values in a column
...aggregate function:
SELECT COUNT(DISTINCT column_name) AS some_alias FROM table_name
This will count only the distinct values for that column.
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How do I drop a foreign key in SQL Server?
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Try
alter table company drop constraint Company_CountryID_FK
alter table company drop column CountryID
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How to select records from last 24 hours using SQL?
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SELECT *
FROM table_name
WHERE table_name.the_date > DATE_SUB(CURDATE(), INTERVAL 1 DAY)
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When should I use a composite index?
For example, I have a homes table:
9 Answers
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How can I remove specific rules from iptables?
...l HTTP and HTTPS services on the ports 8006 and 8007 respectively. I use iptables to "activate" the server; i.e. to route the incoming HTTP and HTTPS ports:
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Select last row in MySQL
How can I SELECT the last row in a MySQL table?
10 Answers
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How to map a composite key with JPA and Hibernate?
...// getters, setters
}
The IdClass annotation maps multiple fields to the table PK.
With EmbeddedId
The class for the composite primary key could look like (could be a static inner class):
@Embeddable
public class TimePK implements Serializable {
protected Integer levelStation;
protecte...