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App Inventor 2 拓展参考文档 · App Inventor 2 中文网
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【FTP】App Inventor 2 FTP 上传下载全方案总结
【MD5、密码安全】Encrypt.Security 安全性扩展：MD5哈希，SHA1和SHA256哈希，AES加密/解密，RSA加密/解密，BASE64编码/解码
【AES加解密】MareshaAES 拓展：AES加解密算法
【CRC校验】App Inven...
How do I check to see if a value is an integer in MySQL?
...e REGEXP operator, matching the string to a regular expression. Simply do
select field from table where field REGEXP '^-?[0-9]+$';
this is reasonably fast. If your field is numeric, just test for
ceil(field) = field
instead.
...
MySQL/Amazon RDS error: “you do not have SUPER privileges…”
...e “Parameter Groups” tab.
Create a new Parameter Group. On the dialog, select the MySQL family compatible to your MySQL database version, give it a name and confirm.
Select the just created Parameter Group and issue “Edit Parameters”.
Look for the parameter ‘log_bin_trust_function_creators...
MySQL - force not to use cache for testing speed of query
...ACHE (MySQL 5.7) option in your query.
(MySQL 5.6 users click HERE )
eg.
SELECT SQL_NO_CACHE * FROM TABLE
This will stop MySQL caching the results, however be aware that other OS and disk caches may also impact performance. These are harder to get around.
...
MySQL Query GROUP BY day / month / year
... for added clarity in some cases such as where records span several years. SELECT COUNT(event_id), DATE_FORMAT(event_start, '%Y/%m')
– Ric
Apr 4 '13 at 10:25
...
PDO MySQL: Use PDO::ATTR_EMULATE_PREPARES or not?
... I'm using caches on multiple levels anyway. You can always explicitly use SELECT SQL_CACHE <rest of statement> though.
– Will Morgan
May 4 '12 at 16:37
...
Remote connect to clearDB heroku database
...
In heroku website, go to My Apps and select the app on which you have installed ClearDB.
On the top corner click on Addons and then select ClearDB MySQL Database.
Once there, click on your database and choose the 'Endpoint Information' tab. There you see your ...
Mysql error 1452 - Cannot add or update a child row: a foreign key constraint fails
... have to get rid of those first.
Here's a query that can find those IDs:
SELECT DISTINCT sourcecode_id FROM
sourcecodes_tags tags LEFT JOIN sourcecodes sc ON tags.sourcecode_id=sc.id
WHERE sc.id IS NULL;
share
...
Get the new record primary key ID from MySQL insert query?
...
Eg:
INSERT INTO table_name (col1, col2,...) VALUES ('val1', 'val2'...);
SELECT LAST_INSERT_ID();
This will get you back the PRIMARY KEY value of the last row that you inserted:
The ID that was generated is maintained in the server on a per-connection basis. This means that the value returne...
MySQL Great Circle Distance (Haversine formula)
...ults. To search by kilometers instead of miles, replace 3959 with 6371.
SELECT id, ( 3959 * acos( cos( radians(37) ) * cos( radians( lat ) )
* cos( radians( lng ) - radians(-122) ) + sin( radians(37) ) * sin(radians(lat)) ) ) AS distance
FROM markers
HAVING distance < 25
ORDER BY distance ...