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Why does PostgreSQL perform sequential scan on indexed column?
Very simple example - one table, one index, one query:
4 Answers
4
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MySQL order by before group by
...hor is to use a subquery to return the max date and then join that to your table on both the post_author and the max date.
The solution should be:
SELECT p1.*
FROM wp_posts p1
INNER JOIN
(
SELECT max(post_date) MaxPostDate, post_author
FROM wp_posts
WHERE post_status='publish'
...
How Do I Get the Query Builder to Output Its Raw SQL Query as a String?
...
Use the toSql() method on a QueryBuilder instance.
DB::table('users')->toSql() would return:
select * from `users`
This is easier than wiring up an event listener, and also lets you check what the query will actually look like at any point while you're building it.
...
What is the difference between user and kernel modes in operating systems?
... the application with a private virtual address space and a private handle table. Because an application's virtual address space is private, one application cannot alter data that belongs to another application. Each application runs in isolation, and if an application crashes, the crash is limited ...
GCC -fPIC option
...DIT: In response to comment.
If your code is compiled with -fPIC, it's suitable for inclusion in a library - the library must be able to be relocated from its preferred location in memory to another address, there could be another already loaded library at the address your library prefers.
...
Which MySQL datatype to use for an IP address? [duplicate]
... INT UNSIGNED
And INET_ATON and INET_NTOA to convert them:
INSERT INTO `table` (`ipv4`) VALUES (INET_ATON("127.0.0.1"));
SELECT INET_NTOA(`ipv4`) FROM `table`;
For IPv6 addresses you could use a BINARY instead:
`ipv6` BINARY(16)
And use PHP’s inet_pton and inet_ntop for conversion:
'INSER...
What is an ORM, how does it work, and how should I use one? [closed]
...(book);
}
With an ORM library, it would look like this:
book_list = BookTable.query(author="Linus");
The mechanical part is taken care of automatically via the ORM library.
Pros and Cons
Using ORM saves a lot of time because:
DRY: You write your data model in only one place, and it's easier...
Correct use of Multimapping in Dapper
...rId.
There is a big caveat here, if the column ordering in the underlying table is flipped for some reason:
ProductID | ProductName | AccountOpened | CustomerName | CustomerId
--------------------------------------- -------------------------
splitOn: CustomerId will result in a null custo...
How do I set the time zone of MySQL?
...ed timezones like 'Europe/Helsinki' means that you have to have a timezone table properly populated.)
Keep in mind that +02:00 is an offset. Europe/Berlin is a timezone (that has two offsets) and CEST is a clock time that corresponds to a specific offset.
@@session.time_zone variable
SELECT @@ses...
How to use NULL or empty string in SQL
...
Select *
From Table
Where (col is null or col = '')
Or
Select *
From Table
Where IsNull(col, '') = ''
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