大约有 40,000 项符合查询结果（耗时：0.0355秒） [XML]
Rank function in MySQL
...
One option is to use a ranking variable, such as the following:
SELECT first_name,
age,
gender,
@curRank := @curRank + 1 AS rank
FROM person p, (SELECT @curRank := 0) r
ORDER BY age;
The (SELECT @curRank := 0) part allows the variable initializatio...
Joining two lists together
...eserves the order of the lists, but it doesn't remove any duplicates which Union would do.
This does change list a. If you wanted to preserve the original lists then you should use Concat (as pointed out in the other answers):
var newList = a.Concat(b);
This returns an IEnumerable as long as a i...
Union of dict objects in Python [duplicate]
How do you calculate the union of two dict objects in Python, where a (key, value) pair is present in the result iff key is in either dict (unless there are duplicates)?
...
SQL/mysql - Select distinct/UNIQUE but return all columns?
...
You're looking for a group by:
select *
from table
group by field1
Which can occasionally be written with a distinct on statement:
select distinct on field1 *
from table
On most platforms, however, neither of the above will work because the behavior o...
MySQL table is marked as crashed and last (automatic?) repair failed
... This was a quick fix! Had a "bad" options table. Make sure that you select the correct database first !
– jyllstuart
Jan 10 '19 at 15:54
add a comment
...
How do I split a string so I can access item x?
...0,
PATINDEX('%|%', @products))
SELECT @individual
SET @products = SUBSTRING(@products,
LEN(@individual + '|') + 1,
LEN(@products))
END
ELSE
BEGIN
SET @individu...
How can you determine how much disk space a particular MySQL table is taking up?
...
For a table mydb.mytable run this for:
BYTES
SELECT (data_length+index_length) tablesize
FROM information_schema.tables
WHERE table_schema='mydb' and table_name='mytable';
KILOBYTES
SELECT (data_length+index_length)/power(1024,1) tablesize_kb
FROM information_schema....
ROW_NUMBER() in MySQL
...asy, but actually it kind of isn't).
I often plump for a null-self-join:
SELECT t0.col3
FROM table AS t0
LEFT JOIN table AS t1 ON t0.col1=t1.col1 AND t0.col2=t1.col2 AND t1.col3>t0.col3
WHERE t1.col1 IS NULL;
“Get the rows in the table for which no other row with matching col1,col2 has a hi...
设置用户默认权限 Umask命令详解 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...最终的权限变成了755（777 – 022）。
顺便再介绍一下如何方便的修改目录或文件的权限：
shell> find /path -type d -print0 | xargs -0 chmod 755
shell> find /path -type f -print0 | xargs -0 chmod 644
本次补习班下课！
Umask 默认权限
How can I get the intersection, union, and subset of arrays in Ruby?
...et operations on arrays by doing &(intersection), -(difference), and |(union).
Obviously I didn't implement the MultiSet to spec, but this should get you started:
class MultiSet
attr_accessor :set
def initialize(set)
@set = set
end
# intersection
def &(other)
@set & o...