Ví dụ về việc sử dụng The primary key trong Tiếng anh và bản dịch của chúng sang Tiếng việt
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Note below how I don't need to manually manage the primary key/foreign key relationships.
Note the three indexes in this definition: the primary key index plus the two secondary indexes we defined.
This is because the primary key value is used to identify individual tuples in a relation.
It acts as a cross-reference between tables because it references the primary key of another table, thereby establishing a link between them.
Truely, the primary key. And that is the first key to the mothers' secret.
Consider the following definition of the table Orders, which defines a foreign key relationship referencing the primary key of the Customers table.
Any columns that link to another table should be named the same as the primary key of that table.
For example, assume we have a usertable with a numeric ID(the primary key) and an email address.
drag the primary key from the table on the"one" side of the relationship and drop it onthe relationship.">
Cascade(chain effect): If the value is changed, the Primary Key Foreign Key corresponding to the numbers in the records of the table side nhiều(∞) is changed.
An association between two tables in which the primary key value of each record in the primary table corresponds to the value in the matching field or fields of one, and only one,
Nullify(to NULL): If Row is deleted contains the Primary Key Foreign Key correspondingto the numbers in the records of the table side nhiều(∞) is changed to NULL, so that suggests not to go to find more information any where.
remove duplicate from and click Primary Key to make it as the primary key column. See screenshot.
An association between two tables in which the primary key value of each record in the primary table corresponds to the value in the matching field or fields of many records in the related table.
Second normal form states that it should meet all the rules for 1NF and there must be no partial dependences of any of the columns on the primary key.
appear in this article, they include the primary key field, and the field is renamed as described by using the preceding steps.
take the primary key on the"one" side of the relationship and add it as an additional fieldthe relationship.">
take the primary key on the"one" side of the relationship and add it as an additional columnthe relationship.">