大约有 30,000 项符合查询结果（耗时：0.0332秒） [XML]
What is the most efficient/elegant way to parse a flat table into a tree?
... syntax.
WITH RECURSIVE MyTree AS (
SELECT * FROM MyTable WHERE ParentId IS NULL
UNION ALL
SELECT m.* FROM MyTABLE AS m JOIN MyTree AS t ON m.ParentId = t.Id
)
SELECT * FROM MyTree;
I tested recursive queries in MySQL 8.0 in my presentation Recursive Query Throwdown in 2017.
Below is...
Parsing a string into a boolean value in PHP
...e {
// "none" gets special treatment to be consistent with ini file behavior.
// see documentation in php.ini for more information, in part it says:
// "An empty string can be denoted by simply not writing anything after
// the equal sign, or by usin...
Find all records which have a count of an association greater than zero
... To remove the duplicates, use
Project.joins(:vacancies).group('projects.id')
UPDATE:
As pointed out by @Tolsee, you can also use distinct.
Project.joins(:vacancies).distinct
As an example
[10] pry(main)> Comment.distinct.pluck :article_id
=> [43, 34, 45, 55, 17, 19, 1, 3, 4, 18, 44, ...
Stateless vs Stateful - I could use some concrete information
...th ASP.NET web apps :) But if you think of a static website with only HTML files and images, you'll know what I mean.
share
|
improve this answer
|
follow
|
...
SQL join: selecting the last records in a one-to-many relationship
...mmend solving it:
SELECT c.*, p1.*
FROM customer c
JOIN purchase p1 ON (c.id = p1.customer_id)
LEFT OUTER JOIN purchase p2 ON (c.id = p2.customer_id AND
(p1.date < p2.date OR (p1.date = p2.date AND p1.id < p2.id)))
WHERE p2.id IS NULL;
Explanation: given a row p1, there should be no ro...
How to reset postgres' primary key sequence when it falls out of sync?
...
-- Login to psql and run the following
-- What is the result?
SELECT MAX(id) FROM your_table;
-- Then run...
-- This should be higher than the last result.
SELECT nextval('your_table_id_seq');
-- If it's not higher... run this set the sequence last to your highest id.
-- (wise to run a quick pg...
javascript find and remove object in array based on key value
...been trying several approaches on how to find an object in an array, where ID = var, and if found, remove the object from the array and return the new array of objects.
...
Bootstrap modal appearing under background
... we changed over to generating our SASS and completely forgot about the js file itself.. This needs to be the top answer.. As our modal is always by default included just before the body close tag...
– Angry 84
Sep 15 '16 at 0:40
...
Looking for a clear definition of what a “tokenizer”, “parser” and...
...izer or vice versa)? I need to create a program will go through c/h source files to extract data declaration and definitions.
...
How can I list all foreign keys referencing a given table in SQL Server?
...s...
select
t.name as TableWithForeignKey,
fk.constraint_column_id as FK_PartNo, c.
name as ForeignKeyColumn
from
sys.foreign_key_columns as fk
inner join
sys.tables as t on fk.parent_object_id = t.object_id
inner join
sys.columns as c on fk.parent_object_id = c.object...