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使用 C++ 处理 JSON 数据交换格式 - C/C++ - 清泛网 - 专注C/C++及内核技术
...输格式。
本文并不详细介绍 JSON 本身的细节，旨在讨论如何使用 C++ 语言来处理 JSON。关于 JSON 更具体的信息，可参见 JSON 官网：http://www.json.org。
二、本文选择处理 JSON的 C++ 库
本文选择一个第三方库 jsoncpp 来解析 JSON。...
MySQL selecting yesterday's date
...get yesterday's date is:
subdate(current_date, 1)
Your query would be:
SELECT
url as LINK,
count(*) as timesExisted,
sum(DateVisited between UNIX_TIMESTAMP(subdate(current_date, 1)) and
UNIX_TIMESTAMP(current_date)) as timesVisitedYesterday
FROM mytable
GROUP BY 1
For the ...
“INSERT IGNORE” vs “INSERT … ON DUPLICATE KEY UPDATE”
...int, unique key (u));
mysql> insert into foo (u) values (10);
mysql> select * from foo;
+----+------+
| id | u |
+----+------+
| 1 | 10 |
+----+------+
mysql> show create table foo\G
CREATE TABLE `foo` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`u` int(11) DEFAULT NULL,
...
How to declare a variable in MySQL?
...at has not been
initialized, it has a value of NULL and a type of string.
SELECT @var_any_var_name
You can initialize a variable using SET or SELECT statement:
SET @start = 1, @finish = 10;
or
SELECT @start := 1, @finish := 10;
SELECT * FROM places WHERE place BETWEEN @start AND @finish...
你真的了解熊市有多么可怕吗？ - 创意 - 清泛网 - 专注C/C++及内核技术
...情，因为天天都是跌。
每天出现的股评高手，说的都是如何杀跌换股，短线操作而不是持有。
每隔几周，都会出现新底，而且每次有人叫着抄底，接下来就继续地下跌，跌到最后没人说抄底为止。国家出台超过3个以上的利好...
如何选择机器学习算法 - 大数据 & AI - 清泛网移动版 - 专注C/C++及内核技术
如何选择机器学习算法Choosing-a-Machine-Learning-Classifier如何针对某个分类问题决定使用何种机器学习算法？ 当然，如果你真心在乎准确率，最好的途径就是测试一大堆各式各样的算法（同时确保在每个算法上也测试不同的参数），...
MySQL get row position in ORDER BY
...
Use this:
SELECT x.id,
x.position,
x.name
FROM (SELECT t.id,
t.name,
@rownum := @rownum + 1 AS position
FROM TABLE t
JOIN (SELECT @rownum := 0) r
ORDER BY t.name)...
MySQL - Get row number on select
Can I run a select statement and get the row number if the items are sorted?
5 Answers
...
Can I store images in MySQL [duplicate]
...t to save the thumbs (since they are very small) in the database and I use MySQL. (I don't want to save the thumbs as physical files on the drive.)
Does MySQL allow saving and retrieving image data and how do I go about it? If it doesn't support image data, is there any free database that does? I ...
MySQL SELECT WHERE datetime matches day (and not necessarily time)
...
NEVER EVER use a selector like DATE(datecolumns) = '2012-12-24' - it is a performance killer:
it will calculate DATE() for all rows, including those, that don't match
it will make it impossible to use an index for the query
It is much fas...