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Environment: NavicatforMysql8.2MySQLSever5.1 problem: Add a foreign key in NavicatforMysql solution: Method 1: use an SQL statement to create a foreign key: altertable foreign key table addconstraint constraint name foreignkey (column name)

I. Basic Concepts 1. MySQL has the same definition of "key" and "Index", so foreign keys and primary keys are also an index. The difference is that MySQL will automatically index the primary keys of all tables, but the foreign key field must be

Grammar [CONSTRAINT [Symbol]] FOREIGN KEY[Index_name] (Index_col_name, ...)REFERENCES tbl_name (Index_col_name,...)[on DELETE Reference_option][on UPDATE Reference_option] Reference_option:RESTRICT | CASCADE | SET NULL | The use of the NO ACTION

First, the basic concept1, MySQL "key" and "index" definition is the same, so the foreign key and the primary key is also one of the index. The difference is that MySQL automatically indexes the primary key for all tables, but the foreign key field

SQLite foreign KEY (Foreign key) supportFOREIGN KEY constraints are supported starting from SQLite 3.6.19. (The SQLite version of Ubuntu 10.04 is 3.6.22, and the SQLite version of Debian 6.0 is 3.7.0)A FOREIGN KEY constraint is used to enforce a

Original address: http://www.2cto.com/database/201501/367791.htmlFirst, the basic concept1, MySQL "key" and "index" definition is the same, so the foreign key and the primary key is also one of the index. The difference is that MySQL automatically

Business Requirements: User table R_user Save the user name and other information. Now need to set up a work base for each user, a user can have more than one work base, multiple users can also have a work base, that is, many-to-many relationships. (

A foreignkey is a relationship that is established when a one-to-many relationship:a foreign key is a field in a table that matches another field in another table. foreign keys impose restrictions on data in related tables, which allows MySQL to

We usually have this requirement: delete the records in Table 1, and you need to delete several records related to table 1 in the other tables.For this, we have two workarounds:One, foreign key constraints using the InnoDB tableALTER TABLE ' score

First, the basic concept1, MySQL "key" and "index" definition is the same, so the foreign key and the primary key is also one of the index. The difference is that MySQL automatically indexes the primary keys for all tables, but the foreign key

1. Why do SQL Server table names add square brackets?This is not required, but if the table name or field name references a keyword in SQL Server, the database does not recognize whether this is a keyword or a table name (or field name) that must be

About PDO PDO is a "database access abstraction Layer" that unifies various databases (MySQL, MSSQL, Oracle, DB2, PostgreSQL ...). ), it is easy to switch between different databases, which makes porting between databases easy to implement. PDO

MYSQL foreign key (ForeignKey) BitsCN.com MySQL 3.23.44 and later versions support foreign key constraints for InnoDB engine tables. Usage conditions of foreign keys: 1. the two tables must be InnoDB tables, and MyISAM tables do not currently

Mysql foreign key BitsCN.com In MySQL, tables of the InnoDB engine type support foreign key constraints.Usage conditions of foreign keys:1. the two tables must be InnoDB tables, and MyISAM tables do not currently support foreign keys (it is said

MySQL has two common engine types: MyISAM and InnoDB. Currently, only the InnoDB engine type supports foreign key constraints. The syntax for defining foreign key constraints in InnoDB is as follows:[CONSTRAINT [symbol] FOREIGN KEY[Index_name]

Example: [java] package Utils; import java. SQL. connection; import java. SQL. driverManager; import java. SQL. resultSet; import java. SQL. SQLException; import java. SQL. statement; public class DB {private static Connection con = null; private

Statement: The material used in this column is written by the VIP students of the Kay Academy, who has the right to be anonymous and has the final right to interpret the article; The Edith Academy is designed to promote students to learn from each

Racle uses foreign keys to restrict the referenced field values in the child table, requiring that the data in the child table be present in the primary table. When a foreign key reference unique constraint value changes when the record of the

In MySQL, a table with the InnoDB engine type supports foreign key constraints.Use conditions for foreign keys:1. Two tables must be INNODB tables, MyISAM table temporarily does not support foreign keys (it is said that future versions may be

If Table A's primary key is a field in table B, the field is called the Foreign key of Table B, table A is called the primary table, and table B is called from the table. Foreign keys are used to achieve referential integrity, and different foreign