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constraint constraintFirst article: Five kinds of constraints1. Primary KEY ConstraintsCREATE TABLE T (i int primary key)--constraint name is automatically generated by the system ALTER TABLE DBO.T ADD constraint T_PK primary key (i)The index is

Original link: http://www.cppblog.com/wolf/archive/2014/05/09/69089.htmlAfter MySQL version 3.23.44, the InnoDB Engine type table supports foreign KEY constraints. Use conditions for foreign keys:1. Two tables must be a InnoDB table, the MyISAM

The use of foreign keys in MySQL to implement cascade Delete, updateMySQL supports foreign key storage engine only InnoDB, when creating foreign keys,Requires that the parent table must have a corresponding index, and the child table will

# # MySQL Database# # # Knowledge Points:1. Data operation increase, delete, change2. FOREIGN KEY constraint requirements3. A one-to-many table relationship4. One-to-one table relationship5. Many-to-many table relationships6. Referential actions for

/* Modify User password:1. Enter CMD to open the DOS window2.sqlplus/nolog3.conn/as SYSDBA4.alter user system identified by ORCL;*//**Data integrity refers to the correct state of all data values stored in the database.If an incorrect data value is

1 FOREIGN key FOREIGN key: Foreign key, outside the key (the key is not in its own table), if a table has a field (non-primary key) to the other table's primary key, then the field is called a foreign key. 1.1 Adding foreign keys

1. Background* MySQL has two commonly used engine types MyISAM and InnoDB. Currently only the InnoDB engine type supports foreign key constraints. * The columns of this table must be the same as the foreign key type, the foreign key must be the

The so-called database is the establishment of the construction of the table constraints.① determines that the entity is determined to have several tables② determining the properties of a tableThree levels of normalization: three paradigms of

One. Common MySQL command-line commands1. Start MySQL service net start MySQLStop MySQL service net stop MySQL2. Netstat–na | findstr 3306 View the port being monitored, findstr is used to find out if there is a port in the back3. Log in to the

Note: This article turns from:http://www.cnblogs.com/smyhvae/p/4042303.htmlThe main contents of this chapter: First, foreign key Second, table connection Third, sub-query Iv. Index First, FOREIGN key: 1. What is a

Use' Wfc_database '; # Main Table (also known as: Referenced table, referencedTable, outtable)ALTER TABLE' App ' ENGINE=innodb;# from a table (also known as: Reference table, appearance, referencingTable)ALTER TABLE' App_version ' ENGINE=innodb;# an

First, FOREIGN key: 1. What is a foreign key 2. Foreign KEY syntax 3, FOREIGN key conditions 4. Add foreign keys 5. Delete foreign keys 1, what is the foreign key:PRIMARY KEY : Uniquely identifies a record, cannot be

This is the case: the user table contains the usernamechar (16) NOTNULLCOMMENT & #039; username & #039;, passwordchar (32) NOTNULLCOMMENT & #039; password & #039;, emailchar (32) NOTNULLCOMMENT & #039; user email & #039;, mobilechar (15)

The CASCADE operation of Oracle is to process the data in the primary table. There are three situations: SETNULL, CASCADE, and NOACTION. Oracle CASCADE operations are designed to process the data in the primary table. There are three situations: set

Oracle notes: Table and field (4) constraints are divided into two types: column constraint and Table constraint. A column constraint is a constraint defined on one column. A Table constraint is a constraint defined on two or more columns.

How can I create a foreign key constraint in Oracle using a non-default method? If the Oracle default creation method is used, the referenced data cannot be deleted, this gives us more flexible options in Oracle9i, however, we use the on delete

Oracle study note (4) Foreign key-create table major_ning (mid number (2) primary key, mname varchar2 (30) referenced in the master table (parent table )); -- from the table (sub-table), refer to the create table student_ning (id number (5) primary

GC has nothing to do with Memory leakage Garbage collection is a traditional topic that has been discussed by countless people. Action Script uses a memory management mechanism similar to Java and does not recycle the memory of discarded objects in

1. Two configuration files:A. hibernate. cfg. xml and B. hibernate. Properties A can contain the configuration of the ing file, while hard codes in B adds the ing file. A. Configuration Config = new configuration (). config ();B. Configuration

In practical applications, when we want to hand over a project to the customer, we need to clear all the previous test data of all tables in the database to give the customer a clean database, if there are many tables involved, it takes not only