On Delete Restrict Mysql

Databases are the basis of E-commerce, finance, and ERP systems, and often hold important business partners and customer information. Electronic data from most businesses, organizations, and government departments are kept in various databases, where they keep personal data and sensitive financial data. But databases are often not as secure as operating systems and networks. Data is the lifeblood of an organization, so it is critical to choose a secure database. I installed the MSSQL and MySQL by default with admin account on my machine to be in the same ...

If a computer manufacturer, its database holds machine and accessories product information. The table used to save the whole product information is called pc; the table used to save the parts supply information is called parts. There is a field in the pc table, used to describe the type of CPU used in this computer; there is a field in the parts table, the description of the CPU model, we can think of it as a list of all CPU models. Obviously, the CPU used by this manufacturer must be a model that exists in the supply information sheet. At this time, two tables ...

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 ...

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The intermediary transaction SEO diagnoses Taobao guest Cloud host technology Hall WDCP is the Wdlinux Control panel abbreviation, is a set of PHP development Linux Server Management system as well as the virtual host management system,, aims at easy to use the Linux system as our website server, as well as usually to 　　Linux Server Common management operations, can be done in the background of WDCP. 　With WDCP, you can easily create Web sites, create FTP, create MySQL databases, and so on. ...

Intermediary transaction SEO diagnosis Taobao guest Cloud host technology Hall with the vigorous development of e-commerce, more and more domestic enterprises began to engage in network marketing, the company's business expansion, at the same time the domestic large and small program developers to provide open source to build a CMS program for E-commerce has contributed to the high speed of the great power. However, because many domestic developers lack of security common sense, so that these open source programs appear a variety of loopholes, small to sdcms, 74cms such a small number of stations to build the program, large to Dedecms, disc ...

Intermediary transaction SEO diagnosis Taobao guest Cloud host technology Hall with the vigorous development of e-commerce, more and more domestic enterprises began to engage in network marketing, the company's business expansion, at the same time the domestic large and small program developers to provide open source to build a CMS program for E-commerce has contributed to the high speed of the great power. However, because many domestic developers lack of security common sense, so that these open source programs appear a variety of loopholes, small to sdcms, 74cms such a small number of stations to build the program, large to Dedecms, disc ...

The intermediary transaction SEO diagnoses Taobao guest Cloud host Technology Hall website completes, the maintenance and the management becomes the work which needs to carry on continuously. 　　In this chapter, the site will be optimized for internal links, efficient maintenance, PR upgrade way to introduce. First, optimize the internal links of the site two, the site efficient maintenance of three common sense three, improve the site PageRank have a coup four, site exchange links to beware of counterfeit five, against the vulgar ban on the site's illegal content six, simple configuration let Web server impregnable ...

Foreign key role: Maintain data consistency, integrity, the main purpose is to control the data stored in the foreign key table. So that the two forms related, the foreign key can only refer to the value of the column in the surface! For example: ab two tables a table has the customer number, customer name b table stored in each customer's order After the foreign key You can only delete clients in Table a if you do not have Customer x in the b table. Prerequisites: The columns in this table must be the same as the foreign keys (the foreign key must be a foreign key). Specify ...

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