First of all, currently in the product environment available MySQL version (referring to 4.0.x and 4.1.x), only the InnoDB engine allows the use of foreign keys, so our data table must use the InnoDB engine.Below, we first create the following test database tables: createtable ' ROOTTB ' ( ' id ' int (one) unsignedauto_ Incrementnotnull, ' data ' varchar (notnulldefault) ', PRIMARYKEY (' id ') ) type=innodb; createtable ' SUBTB ' ( ' id ' int (one) unsignedauto _incrementnotnul
Article copyright by the author Xiaohui Li is and the blog park, if reproduced please clearly indicate the source: http://www.cnblogs.com/naaoveGIS/1. BackgroundIn a project, it is found that when a checkbox is added to a tree, it is very slow to initialize it. The nodes in the field tree have a depth of three layers, and the total number of nodes is more than 200. After troubleshooting, the parameter of the tree is turned on the cascade tick, resulti
Cascade Cascade, only affects crud cud and does not affect reads. Do not set cascading, from a party can read one side, set up a cascade, from one side, the default can not read a lot of the party.If there is an association between two objects, whether it's a one-to-many, one-way, or two-way, if from a can be directed to B:A--->bBy default, the save of a does not
Hibernate collection mappings are often used for both "inverse" and "cascade" properties. For me, hibernate contact is not deep and the language level of all kinds of factors, found that these two properties is difficult to understand, helpless had to this two attribute interpretation work to Google and Baidu, see a lot of cow people's explanation, plus their own in the Eclipse debugging, on the " Inverse "and" ca
Because of the time, I am here to test the environment is a one-to-many relationship in the use of the annotated way of cascading, there are a lot of posts on the Internet, I have seen, but, I would like to summarize it, it felt that the cascade is unidirectional, not bidirectional, meaning that, we set two classes of the relationship between objects, Always set in one side is very specific, on the other side to set a mappedby, but if you want both si
Personal definition:
Primary prosecution: maintain one side of the joined table, usually the Creator side, which will be more efficient.
Operation Principle: If inverse is set to false, one is set to true.
When cascade is used to check the business status, the value one is true.
I ,?
Inverse acts as the party holding the set object and determines whether to control the entire set. true --- No, it is only configured in one-to-pair and allow-to-pai
We need to pay attention to the integrity of references when designing databases. During my career as a DBA, I saw many designs taking an extreme path.
Before entering the detailed description of the delete cascade option, let's take a look at another option. You can set the udpate cascade option in a table with a foreign key. In my career, I have never met the need to update one or more columns with fore
First, Introduction:The AdaBoost classifier is composed of Cascade classifiers, which means that the final classifier is composed of several simple classifiers cascade. In the image detection, the inspection window through each level classifier, so that in the previous layer of detection in most of the candidate areas are excluded, all through the detection of each level of the area is the target area.Once
Stacking order and cascading context are two concepts, but they have an inseparable relationship, stacking order is very simple ^_^, serious thinking can be, and the stack context is insignificant, I just need to move the red line you understand, all said, is too simple. The first paragraph is difficult to understand, mainly with this article, only to resolve the displacement. Talk less, see the sword.
In consideration of the possibility that two elements overlap, the concept of
"Problems encountered by your project":New delete can be implemented, that is, when the change cannot be synchronized update design three classes: Problem class Scask body content class Text Class View number + reply number + discussion number of Runinfo class"Body class and number of views + replies + Number of discussion classes cannot be modified update"Background changed annotation success"Reference blog: http://blog.sina.com.cn/s/blog_9b81777f0101gn3f.html"
Explain inverse (relational operations) and (cascade) operations with user, role, and user files as an exampleInverse evaluates to True (does not maintain relationship) or false (Maintenance relationship defaults to false) This property primarily operates on foreign keysCascade value Null (default), Save-update, all, deleteUsers, roles are many-to-many relationshipsThe user's mapping file represents:。。。。。 Inverse= "true" order-by= "progresstime desc
control: If the deleted record has been referenced by foreign key, will error, violate the main foreign KEY reference constraint! If the deleted records are not referenced, you can delete them directly.Cascade PropertyCascade indicates that a cascade operation "can be set to one or more of the other side"None cascade operation, default valueSave-update Cascade S
Setname= "FB"Cascade= "All-delete-orphan"Inverse= "true"Lazy= "false">Key>columnname= "zb_id"Not-null= "true" />Key>One-to-manyclass= "Gov.gzgs.djrwtx.bo.PxglFb" />Set> Both of these properties are used in a multiple-or many-to-many relationship. Inverse, especially for bidirectional relationships, is not needed in a one-way relationship. Cascade represents whether a
MySQL various cascade queries after update (update Select).CREATE TABLE ' tb1 ' (' id ' int (one) is not NULL,' A ' varchar (+) default NULL,' B ' varchar (+) default NULL,' C ' varchar default NULL,PRIMARY KEY (' id '),KEY ' id ' (' ID ')) Engine=innodb DEFAULT charset=latin1;CREATE TABLE ' TB2 ' (' id ' int (one) is not NULL,' A ' varchar (+) default NULL,' B ' varchar (+) default NULL,PRIMARY KEY (' id '),KEY ' id ' (' ID ')) Engine=innodb DEFAULT
Encountered a more regretful thing, using Hibernate's merge and cascade= "All-delete-orphan", the child table data was deleted.
1, use cascade= "All-delete-orphan" To do the cascade delete operation, but please be careful and gethibernatetemplate (). Merge (entity), parameters used together, when using such a combination,
Hibernate executes the gethibernatetempl
Oracle uses on delete cascade and on delete set null to create a foreign key. In this section, we introduce the default creation method of oracle when creating a foreign key constraint, when the referenced data is deleted, it cannot be deleted. This gives us more flexible options in oracle9i, however, we use the on delete cascade and on delete set null keywords to determine whether to delete the data refere
One-to-many relationship mappingsThe Set node information is configured in a one-party configuration file:The properties of the set node in the *.hbm.xml configuration file:Lazy: The default is true to use lazy loading, false for instant loading;Order-by: A party to a set set of multiple entities within a set of the sort method by default is the primary key sort but can be changed;Cascade: Whether to use cascade
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