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/************************************************mysql Database View related Information statement *****************************************/SELECT version ();--View the database revision numberSELECT user (), current_user ();--Production view

If you use the Oracle default creation method when you create a foreign key constraint, it cannot be deleted when the referenced data is deleted, which gives us more flexibility in oracle9i, but we use on DELETE cascade and on delete set Null

If you use the default Oracle creation method when creating foreign key constraints, you cannot delete the referenced data. This gives us more flexible options in Oracle9i, however, we use the on delete cascade and on delete set null keywords to

Reference | Reference Manual | Chinese 4 establish InnoDB table Suppose you have run the MySQL client program as a MySQL test command. In order to create a table in InnoDB format you must specify TYPE = InnoDB in the SQL command: CREATE TABLE

This article mainly introducesOracleNon-default creation of Foreign keys is much better than the default creation method of Oracle, which can solve the inconvenience caused by the default creation method of Oracle, I hope the content involved in

Mysql field type summary --- field type summary table original Web site: http://kimbriggs.com/computers/computer-notes/mysql-notes/mysql-data-types-50.file Type {storage} Name Range Attributes Default Numeric{1 byte}

Use on DELETE cascade and on delete set NULL in Oracle to establish foreign keysThe surface we describe the creation of a foreign key constraint when using the Oracle default creation method, when deleting the referenced data will not be deleted,

Mysql field type source Web site: http://kimbriggs.com/computers/computer-notes/mysql-notes/mysql-data-types-50.file Type {storage} Name Range Attributes Default Numeric{1 byte} TINYINT [(M)] -From 128 TO 127[0

Oracle foreign key cascade deletion and cascade updateCascading Deletion Oracle has three behaviors: no action (similar to RESTRICT), CASCADE, and set null. The following uses the student-class as an example to describe how to delete Foreign keys in

Oracle foreign key cascade deletion and cascade update, oracle key level update Cascading Deletion Oracle has three behaviors: no action (similar to RESTRICT), CASCADE, and set null. The following uses the student-class as an example to describe

cascading queriesthere is a way to implement cascading queries in Oracle databases SELECT * //fields from table///To query with the child contact ID and the parent Contact ID's Table start with selfid=id ///Given a startid (field

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

Cascade Delete, such as when you delete a table and then add the keyword, will delete the table and delete the relationship between the tableotherObject1. Cascade delete the information in table A, when the field in table A refers to the field in

1. Shielding SIGUSR1 signals in the main thread2. creat the two subthreads write and read to cancel the blocking of SIGUSR1 in the write thread. 3. The SIGUSR1 signal sent from other processes will be accepted by the write thread. Sigprocmask is

Reprint Address: http://hi.baidu.com/jxqlovejava/item/3d2cc5b5d689917c244b0920?Look at the on Delete property first, possibly with a value such as: No Action, Cascade,set Null, restrict property.When the value is no action or restrict, when the

Mysql-InnoDB storage engine Foreign key constraint -- (ForeignKeyConstraint) Mysql foreign key SQL foreign key constraints The foreign key in one table points to the primary key in another table. The foreign key constraint is used to prevent the

--======= test: FOREIGN key =========-------=======auther:su=========-------=======time:2015-06-26===-------=========================-------******* Theory Knowledge **********-------=========================-------Add foreign key when adding table:

Each thread has its own signal shielding word, but the signal processing is shared by all threads in the process. This means that although a single thread can block some signals, when the thread modifies the processing behavior related to a certain

1 Cascade DeleteOracle Delete on foreign keys has no action (similar to restrict), cascade, and set null three behavior.Below the student-class as an example to explain the foreign key deletion under different circumstances, students belong to the

This article mainly introduces someMySQL databaseOfForeign key constraintNext, let's take a look at it. Foreign key constraints must meet the following conditions: Both parent and child tables are innodb, not temporary tables. In a sub-table, an