大约有 19,000 项符合查询结果（耗时：0.0384秒） [XML]
使用虚拟现实和App Inventor进行实验 · App Inventor 2 中文网
...Google 商店以查找各种 Cardboard 查看器，或在网上搜索有关如何制作自己的 Cardboard 查看器的提示。您还可以使用 Cardboard 以外的查看器。
Expeditions
Expeditions 演示显示沉浸式 360 度全景图。Google 于 2014 年在 Google I/O 2014 的主题演讲...
Are duplicate keys allowed in the definition of binary search trees?
...a BST which allows either of the right or left children to be equal to the root node, will require extra computational steps to finish a search where duplicate nodes are allowed.
It is best to utilize a list at the node to store duplicates, as inserting an '=' value to one side of a node requires r...
SQL Add foreign key to existing column
...
MySQL / SQL Server / Oracle / MS Access:
ALTER TABLE Orders
ADD FOREIGN KEY (P_Id)
REFERENCES Persons(P_Id)
To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN KEY constraint on multiple columns, use th...
Drop all tables whose names begin with a certain string
...
MYSQL: SELECT concat('DROP TABLE ',TABLE_NAME,";") as data FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME LIKE '[prefix]%' --- for those who like me found this thread
– Andre
Nov 6 '12...
MySQL Data - Best way to implement paging?
My iPhone app connects to my PHP web service to retrieve data from a MySQL database. A request can return 500 results.
7 An...
Select last row in MySQL
How can I SELECT the last row in a MySQL table?
10 Answers
10
...
How can I include a YAML file inside another?
...custom constructors (such as !include) to the YAML loader. I've included a root directory that can be set so that this solution supports relative and absolute file references.
Class-Based Solution
Here is a class-based solution, that avoids the global root variable of my original response.
See th...
MySQL SELECT only not null values
...WHERE YourColumn IS NOT NULL;
Just for completeness I'll mention that in MySQL you can also negate the null safe equality operator but this is not standard SQL.
SELECT *
FROM table
WHERE NOT (YourColumn <=> NULL);
Edited to reflect comments. It sounds like your table may not be in first ...
MySQL combine two columns into one column
...
My guess is that you are using MySQL where the + operator does addition, along with silent conversion of the values to numbers. If a value does not start with a digit, then the converted value is 0.
So try this:
select concat(column1, column2)
Two way...
How to use GROUP BY to concatenate strings in MySQL?
... 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 result with the concatenated non-NULL values from a group. It returns NULL if there ...