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Web API 最佳入门指南 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...他同类型框架的对比，最后通过一些相对复杂的实例展示如何通过WebAPI构建http服务，同时也展示了VisualStudio构建.net项目的各种强大。Web API是一个比较宽泛的概念。这里我们提到Web API特指ASP.NET Web API。
这篇文章中我们主要介绍...
How to get the number of days of difference between two dates on mysql?
...lues are
used in the calculation
In your case, you'd use :
mysql> select datediff('2010-04-15', '2010-04-12');
+--------------------------------------+
| datediff('2010-04-15', '2010-04-12') |
+--------------------------------------+
| 3 |
+--------------...
Order a MySQL table by two columns
...h query not working in my case.. Tn this case, I dont get sorting for City select distinct City, Country from customers order by Country desc, City desc;
– Pra_A
Sep 15 '16 at 6:55
...
A better similarity ranking algorithm for variable length strings
...tr2.length-2).collect {|i| str2[i,2]}.reject {
|pair| pair.include? " "}
union = pairs1.size + pairs2.size
intersection = 0
pairs1.each do |p1|
0.upto(pairs2.size-1) do |i|
if p1 == pairs2[i]
intersection += 1
pairs2.slice!(i)
break
end
end
end
(2.0 * inter...
How to run SQL script in MySQL?
... If the purpose of writing to file is taking data dump, I guess SELECT ... INTO OUTFILE /path/to/file.csv is more efficient way. See options and syntax here - dev.mysql.com/doc/refman/5.7/en/select-into.html
– Anis
Feb 21 '18 at 6:43
...
MySql: Tinyint (2) vs tinyint(1) - what is the difference?
...rows affected (0.02 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> SELECT * FROM tin3;
+----+------------+
| id | val |
+----+------------+
| 1 | 0000000012 |
| 2 | 0000000007 |
| 4 | 0000000101 |
+----+------------+
3 rows in set (0.00 sec)
mysql>
mysql> SELECT LENGTH(val)...
When and why are database joins expensive?
...s back to mitigating the size of the working set. Joins involving properly selected keys with correctly set up indexes are cheap, not expensive, because they allow significant pruning of the result before the rows are materialised.
Materialising the result involves bulk disk reads which are the mo...
How to use GROUP BY to concatenate strings in MySQL?
...
SELECT id, GROUP_CONCAT(name SEPARATOR ' ') FROM table GROUP BY id;
http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat
From the link above, GROUP_CONCAT: This function returns a string res...
You can't specify target table for update in FROM clause
...llow you to write queries like this:
UPDATE myTable
SET myTable.A =
(
SELECT B
FROM myTable
INNER JOIN ...
)
That is, if you're doing an UPDATE/INSERT/DELETE on a table, you can't reference that table in an inner query (you can however reference a field from that outer table...)
Th...
SET NAMES utf8 in MySQL?
... client, thus is also needed when receiving this data, using for example a SELECT statement.
– Leopoldo Sanczyk
Nov 20 '15 at 20:54
...