foreign key field access

Label:FOREIGN KEY constraint exception phenomenonIn the following example, there is no insertion failure that violates the referential constraint. create database `a-b`; use `a-b`; SET FOREIGN_KEY_CHECKS=0; create table t1(c1 int primary key, c2 int) engine=innodb; create table t2(c1 int primary key, c2 int) engine=innodb; alter table t2 add

SELECT Table name =case When a.colorder = 1 THEN d.name ELSE "End, Table Description =case When A.colorder = 1 THEN isnull (F.value, ' ") ELSE ' end, Field Ordinal =a.colorder, Field name =a.name, Logo =case when ColumnProperty (a.id, A.name, ' isidentity ') = 1 THEN ' √ ' ELSE ' end, Primary key =case when EXISTS ( SELECT 1 From Dbo.sysindexes si INNER JOIN Dbo.

Parsing MySQL foreign key association error Mysql foreign key BitsCN.com This error often occurs when you try to create a foreign key in mysql, which is very frustrating. You cannot create one. the error of the frm file seems to

; Insertintostudent(student_id,student_name)values(1,'luzl'); Insertintoclass(class_id,class_name)values(1,'db2'); Insertintostudent_class(student_class_id,student_id,class_id)values(1,1,1); 2. Options for On Delete are: Restrict/no action/cascade/set null. if the cascade option is specified, if the parent record is deleted, its child record will be deleted automatically. it is equivalent to cascading deletion. if no action or cascade is specified, an error is returned. As there are

student can only belong to a class, this is a one-to-many relationship;3, many-to-many relationship, need to create a table, the table requires two fields, respectively, is a reference, two many-to-many field primary key foreign key.For example:Student's form (school number, name, ...). ) PRIMARY key: study numberClas

First, prefaceIf there is more than one field in table a associated with another field in table B, it is like the billing address and shipping address of a customer table, along with the ID field in the Address table.Ii. examples#-*-coding:utf-8-*- fromSQLAlchemyImportCreate_engine fromSQLAlchemyImportInteger, ForeignKey, String, Column fromSqlalchemy.ext.declara

For example, how can I query the number of data entries corresponding to the foreign key of a table based on the id of the primary table from the table's reid to the id field of the primary table? For example, if reid is 1 and all point to the row with the primary table id 1, how many data entries can be queried by id? For example, how can I query the number of

cannot understand it. However, after a period of training, the situation has been greatly improved: not only can you understand, but also can hear quickly; not only can your listening level be improved, but also your oral level be improved. This shows that both listening and speaking are completely different. 　　ThirdEight years of foreign affairs translation work has made our language expressions more standardized and accurate. After graduating from

The MySQL database was used today. The visual management tool initially used is the MySQL GUI Tools officially recommended. It will be easier to change to phpMyAdmin if it is not easy to use, but it is not convenient to set the foreign key, if you decide to enter the command line mode, the foreign key setting statement

There are two of these sql:Insert Table_a (bId) value (1);--sql-1 update table_b set b.xx=123 where b.id = 1; --Sql-2Where the Table_a field bid is a foreign key, and the foreign key is associated with the ID field of the Table_b.

joined"Display table"The dialog box is not displayed. Click"Display table". Double-click the table name and close the "show tables" dialog box. To establish a relationship between the table and itself, add the table twice. Drag the required field from a table to another table.To drag multiple fields, press Ctrl, click each field, and drag these fields.In most cases, the primary

product album table, Ru_products and ru_pro_images are 1:n relations; The requirement now is that when you delete a product, all of the album data for that item is deleted, in two ways:Way one: Implement in code, delete deletes from ru_products ... Select the ID of the data before, and then, based on this ID, delete the ru_images tablepro_id = ID of the data;Mode two: In the CREATE table ru_images, the establishment of foreign

Set one-to-one foreign key associations. You can find the wife through husband, but cannot find husband through wife. 1. Write the entity class wife; When annotation is used, the entity class is annotated, @ entity, @ ID Package COM. hibernate. _ 0600_one2one_uni_fk; import javax. persistence. entity; import javax. persistence. ID; @ entitypublic class wife {private integer ID; private string name;

Cannot delete or update a parent row: A foreign key constraint fails ('myreview/zmax_text ', constraint 'zmax _ text_ibfk_1' foreign key ('lang ') references 'zmax _ Lang '('lang '))The above is because a field of the record is changed to the external chain of another table

delete a corresponding relationship:Obj1 = press.objects.get (id = 2)Obj1.books.set (Book.objects.filter (id__in = [4, 5]))Obj1.books.remove (*book.objects.filter (id__in = [4, 5])) Press field set, null = True3. Associated fields:Find the publisher of the book of Happy baseobj = models. Press.objects.filter (id=models. Book.objects.get (title= ' Happy Camp '). press_id)Print (obj)obj = models. Press.objects.filter (books__title= ' Happy Camp '), #涉及

Reposted at: http://blog.csdn.net/donglynn/article/details/17056099error SQL query: Delete from 'zmax _ Lang 'Where convert ('zmax _ Lang'. 'lang 'using utf8) = 'Fr' limit 1 MySQL returns: #1451-cannot delete or update a parent row: A foreign key constraint fails ('myreview/zmax_text ', constraint 'zmax _ text_ibfk_1' foreign

MySQL statement query: Delete from user WHERE uid = 7; Error: 1451-cannot Delete or update a parent ROW:A FOREIGN KEY constraint fails (shop.orders, constraint Fkc3df62e5aa3 D9c7 FOREIGN KEY (UID) REFERENCES user (uid ) ReasonA field in a InnoDB record is used as the outer

This error occurs because the MySQL tutorial has always been unable to support the problem of relationships, unfortunately, it does not indicate which problem is causing the above error, and I list the common causes of this terrible 150 error, and I sort the size of the probabilities, Known reasons: 1, two fields of type or size do not exactly match, for example, if one is int (10), then the foreign key mu

An error like this cannot create a. frm file seems to imply incorrect permissions or other reasons for operating system files, but in reality, this MySQL error has been reported as a bug in MySQL itself and has been in the MySQL developer list for many years, Yet this seems another misleading. In many instances, this error occurs because MySQL has always been unable to support the relationship of the problem, and, unfortunately, it does not indicate exactly which one of the problems will lead t