大约有 37,000 项符合查询结果（耗时：0.0235秒） [XML]
SQL - HAVING vs. WHERE
... hence HAVING works correctly.
As a rule of thumb, use WHERE before GROUP BY and HAVING after GROUP BY. It is a rather primitive rule, but it is useful in more than 90% of the cases.
While you're at it, you may want to re-write your query using ANSI version of the join:
SELECT L.LectID, Fname, L...
Why should the copy constructor accept its parameter by reference in C++?
Why must a copy constructor's parameter be passed by reference?
8 Answers
8
...
Using LIMIT within GROUP BY to get N results per group?
..._CONCAT aggregated function to get all years into a single column, grouped by id and ordered by rate:
SELECT id, GROUP_CONCAT(year ORDER BY rate DESC) grouped_year
FROM yourtable
GROUP BY id
Result:
-----------------------------------------------------------
| ID | GROUPED_YEAR ...
Pass Variables by Reference in Javascript
How do I pass variables by reference in JavaScript? I have 3 variables that I want to perform several operations to, so I want to put them in a for loop and perform the operations to each one.
...
What is the purpose of Order By 1 in SQL select statement?
...code at work, and have noticed that there are several views with an order by 1 clause. What does this accomplish?
8 Ans...
Select top 10 records for each category
... FROM (
SELECT Field1,Field2, Rank()
over (Partition BY Section
ORDER BY RankCriteria DESC ) AS Rank
FROM table
) rs WHERE Rank <= 10
If your RankCriteria has ties then you may return more than 10 rows and Matt's solution may be better for y...
How do you match only valid roman numerals with a regular expression?
...etween 0 and 4000. It's a relatively simple:
0: <empty> matched by M{0}
1000: M matched by M{1}
2000: MM matched by M{2}
3000: MMM matched by M{3}
4000: MMMM matched by M{4}
You could, of course, use something like M* to allow any number (including zero) of thousan...
Are the days of passing const std::string & as a parameter over?
I heard a recent talk by Herb Sutter who suggested that the reasons to pass std::vector and std::string by const & are largely gone. He suggested that writing a function such as the following is now preferable:
...
Select first row in each GROUP BY group?
...I'd like to select the first row of each set of rows grouped with a GROUP BY .
17 Answers
...
LISTAGG in Oracle to return distinct values
...c and later:
select listagg(distinct the_column, ',') within group (order by the_column)
from the_table
18c and earlier:
select listagg(the_column, ',') within group (order by the_column)
from (
select distinct the_column
from the_table
) t
If you need more columns, something like this ...