大约有 40,000 项符合查询结果（耗时：0.0394秒） [XML]
How do I find a “gap” in running counter with SQL?
... FROM mytable mi
WHERE mi.id = mo.id + 1
)
ORDER BY
id
LIMIT 1
In SQL Server:
SELECT TOP 1
id + 1
FROM mytable mo
WHERE NOT EXISTS
(
SELECT NULL
FROM mytable mi
WHERE mi.id = mo.id + 1
)
ORDER BY
...
SQL join: selecting the last records in a one-to-many relationship
... MAX(date) MaxDate
FROM purchase
GROUP BY customer_id
) MaxDates ON c.id = MaxDates.customer_id INNER JOIN
purchase p ON MaxDates.customer_id = p.customer_id
AND MaxDates.MaxDate = p.date
The select should join on all custom...
How to reset postgres' primary key sequence when it falls out of sync?
...LESCE((SELECT MAX(id)+1 FROM your_table), 1), false);
COMMIT;
Source - Ruby Forum
share
|
improve this answer
|
follow
|
...
How to select where ID in Array Rails ActiveRecord without exception
...
If it is just avoiding the exception you are worried about, the "find_all_by.." family of functions works without throwing exceptions.
Comment.find_all_by_id([2, 3, 5])
will work even if some of the ids don't exist. This works in the
user.comments.find_all_by_id(potentially_nonexistent_ids)
...
Finding duplicate values in a SQL table
...
SELECT
name, email, COUNT(*)
FROM
users
GROUP BY
name, email
HAVING
COUNT(*) > 1
Simply group on both of the columns.
Note: the older ANSI standard is to have all non-aggregated columns in the GROUP BY but this has changed with the idea of "functional depe...
How to create a MySQL hierarchical recursive query
... name,
parent_id
from (select * from products
order by parent_id, id) products_sorted,
(select @pv := '19') initialisation
where find_in_set(parent_id, @pv)
and length(@pv := concat(@pv, ',', id))
Here is a fiddle.
Here, the value specified in @pv := '19' shou...
ActiveRecord.find(array_of_ids), preserving order
...suggested something like this:
index = Something.find(array_of_ids).group_by(&:id)
array_of_ids.map { |i| index[i].first }
As efficient as it gets besides letting SQL backend do it.
Edit: To improve on my own answer, you can also do it like this:
Something.find(array_of_ids).index_by(&:...
Why does MYSQL higher LIMIT offset slow the query down?
...MIT offset with SELECT, the slower the query becomes, when using ORDER BY *primary_key*
6 Answers
...
Delete duplicate records in SQL Server?
...
You can do this with window functions. It will order the dupes by empId, and delete all but the first one.
delete x from (
select *, rn=row_number() over (partition by EmployeeName order by empId)
from Employee
) x
where rn > 1;
Run it as a select to see what would be deleted:...
How to find out client ID of component for ajax update/render? Cannot find component with expression
... always give them a fixed ID
If a component which you'd like to reference by ajax process/execute/update/render is inside the same NamingContainer parent, then just reference its own ID.
<h:form id="form">
<p:commandLink update="result"> <!-- OK! -->
<h:panelGroup id="...