How To Use Foreign Key In Mysql

Usually speaking of foreign keys, we only mention "the purpose of the foreign key is to determine the referential integrity of the data." However, what foreign keys specifically include the actions and meanings? 1, set the outer chain: (1), create a foreign key through create table: see 2 lines of code is built in the table command: create table city (... key idx_fk_country_id (country_id), constrain ...

Several guidelines on the establishment of the index: 1, a reasonable indexing can speed up the efficiency of data reading, but unreasonable indexing will slow down the database response speed. 2, the more the index, the slower the update data. 3, try to use the index when using MyIsam as an engine (because MySQL uses BTree to store indexes), not InnoDB. But MyISAM does not support Transcation. 4, when your program and database structure / SQL statement has been optimized to the extent that can not be optimized, and the program bottleneck can not be successfully resolved, then ...

In MySQL, using the id field of the auto_increment type as the primary key of a table and using it as a foreign key to other tables to form a "master-slave table structure" is a common usage in database design. However, in the specific generation of id, our order of operations is generally: insert records in the main table, and then get the automatically generated id, based on it to insert the record from the table. There is a difficulty here, is inserted into the main table record, how to get it corresponds to the id. The usual practice is through "select max (id) from table ...

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StatefulSet problem created in K8s: Pod created using Deployment is stateless, when hanging in the Volume, if the Pod is hung, Replication Controller will run one to ensure availability, but because it is stateless, Pod Hanging up when the relationship with the previous Volume has been disconnected, the new Pod can not find the previous Pod. But for users, they are not aware of the underlying pods, but when the pods hang up ...

Due to the temporary use of foreign space, when I publish a blog, I found that time is always wrong. Based on my previous experience writing programs, this is a time zone problem. This problem is not difficult to solve, write down my solution for future reference. PHP script-side urban settings can be set in php.ini date.timezone key value is 'Asia / Shanghai' can be. But usually the shared virtual host itself does not modify php.ini permissions. This time should be in the public part of the program to join ...

Intermediary trading http://www.aliyun.com/zixun/aggregation/6858.html ">seo diagnose Taobao guest cloud host technology Hall at present, in China has hundreds of thousands of blog sites, the number of blogs is reached millions, and shows a rapid growth trend every year. 　　It's getting easier to build a personal blog now, even if you don't have a bit of programming experience, you can quickly have your own personal independent blog within 5 minutes. Wo ...

Since Amason launched SimpleDB, distributed data storage systems based on Key-value key values have received widespread attention, similar systems include Apache COUCHDB, and the recent blockbuster Google App Engine based on the BigTable Datastore API, there is no doubt that the distributed data storage system provides better lateral scalability, is the future direction of development. But at this stage, compared with the traditional RDBMS, there are some gaps and deficiencies. Ryan P ...

Any web software and applications that need a powerful database to back up, there are countless database management tools online, and developers choose a suitable for their own particularly important.　　This article introduces developers to 10 free database management tools, developers can use them for SQL operations, Multilink, multiple database engine operations, and so on. 1.Open Keyval Open Keyval is an open source free key value database management tool, web-based, and based on PHP development, the goal is to use the simplest way to manage we ...

With the rise of internet web2.0 websites, the relational database has become a very hot new field, the development of the non relational database products is very rapid. 　　But the traditional relational database in dealing with web2.0 website, especially the super large-scale and high concurrent SNS type web2.0 pure dynamic website already appeared to be powerless, has exposed many insurmountable problems, for example: 1, high configured--to the database higher concurrent reads and writes the demand WEB2.0 website to be based on user personalized information to generate real-time dynamic ...