foreign key field access

: When a foreign key is related to a field in another table, and the relationship is temporary, the system is called a state of referential integrity. That is, if a field appears only once in all tables, and the change in this field of each table affects the other t

large-scale systems (performance requirements are not high, high security requirements), the use of foreign keys, in large-scale systems (high performance requirements, security control), no foreign key; small system, the best use of foreign keys.2, use the foreign

I have been developing an information equipment application management system over the past two days. When designing a database, I encountered a tangle problem, that is, the definition of foreign keys, because I don't know which fields need to be defined as foreign keys. Under what circumstances can I define foreign keys and how can I define

primary table as a foreign key, even if the primary key of the primary table should be a unique constraint field as a foreign key Sql> ALTER TABLE Foreign_main add constraint Pk_fsid primary

This foreign key is what, it is not dispensable, feel very mysterious appearance. See a lot of experts are pointing rookie said to do a foreign key, but why do not say, on the fairy go also, hey! Only fish are not to be taught! Reply to discussion (solution) In the relational database, in order to reduce the redu

To add a foreign key to a table must satisfy 2 conditions, 1, the engine of the table must be innodb,2, you must index the field to which you want to add the foreign keyCREATE TABLE Child (CID int NOT NULL Auto_increment primary key,PID int,

key value is updated, it indicates that the database will spread the new key value to the corresponding foreign key field. Cascade deletion related fields Indicates when to delete rows in the master table.DatabaseHttp://blog.csdn.net/shanzhiziremove the corresponding line f

Create a foreign key for a Mysql Cluster. There are four constraints: noaction, restrict, cascade, and setnull. If the primary keyword of Table A is A field in Table B, this field is called the foreign key of Table B. Table A is c

KEY (`blog_id`) REFERENCES `blogs` (`id`) ON UPDATE CASCADE3637) ENGINE = InnoDB DEFAULT CHARSET = utf8; In addition to defining some simple fields for the above two InnoDB tables, the above Code also uses a foreign key constraint, so that whenever the "id" Key of the parent table is updated, the contents

Do I have to have a foreign key in a data table in php? what is this foreign key? is it dispensable and mysterious. I can see that many experts are instructing Cainiao to say they want to create a foreign key, but if you don't wan

Original: powerdesigner-vbsrcipt-Auto set Primary key, foreign key name, etc. (SQL Server)When designing SQL Server datasheets in PowerDesigner, the following functionality is required through VBScript scripting:Primary key: Pk_tablenameFOREIGN key: Fk_tablename_foreignkeyco

/foreign key will add to the development difficulty, resulting in excessive table and other issues 3, without foreign key data management is simple, easy to operate, high performance (import and export operations, in INSERT, UPDATE, delete Data faster) Eg: in a large number of databases do not want to think about

transactions to take during development, because MyISAM tables provide excellent performance. Of course, this is also costly. As I mentioned earlier, applications must maintain database integrity and consistency, this means implementing more complex programming logic to process the relationships between tables. Although database access can be simplified by using the abstraction layer and ORM module, the logic required to process the data tables requi