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mysql Foreign key constraint is incorrectly formed error
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mysql error texts doesn't help so much, in my case, the column had "not null" constraint, so the "on delete set null" was not allowed
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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），...
SQL command to display history of queries
I would like to display my executed sql command history in my MYSQL Query Browser. What is the sql statement for displaying history?
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Gem::LoadError for mysql2 gem, but it's already in Gemfile
...upgrading to rails 4.2.4 (also with rails 4.1.5) try using this version of mysql2:
gem 'mysql2', '~> 0.3.18'
Apparently mysql2 isn't still compatible with newer version of rails because rails 4.2.4 is pretty new as the time of answering this question by me 8 September 2015 so use the above lin...
Update one MySQL table with values from another
I'm trying to update one MySQL table based on information from another.
2 Answers
2
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Is it possible to roll back CREATE TABLE and ALTER TABLE statements in major SQL databases?
...tive.
Is DDL transactional according to this document?
PostgreSQL - yes
MySQL - no; DDL causes an implicit commit
Oracle Database 11g Release 2 and above - by default, no, but an alternative called edition-based redefinition exists
Older versions of Oracle - no; DDL causes an implicit commit
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MySQL Insert into multiple tables? (Database normalization?)
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No, you can't insert into multiple tables in one MySQL command. You can however use transactions.
BEGIN;
INSERT INTO users (username, password)
VALUES('test', 'test');
INSERT INTO profiles (userid, bio, homepage)
VALUES(LAST_INSERT_ID(),'Hello world!', 'http://www.sta...
jQuery UI Sortable, then write order into a database
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this may help you codingbin.com/reorder-with-php-mysql-and-jquery-sortable
– MKD
Mar 2 '17 at 23:51
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What is InnoDB and MyISAM in MySQL?
What is InnoDB and MyISAM in MySQL ?
8 Answers
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MySQL InnoDB not releasing disk space after deleting data rows from table
I have one MySQL table using the InnoDB storage engine; it contains about 2M data rows. When I deleted data rows from the table, it did not release allocated disk space. Nor did the size of the ibdata1 file reduce after running the optimize table command.
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