Referential integrity

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  • [ Team LiB ] Recipe 6.6 Avoiding Referential Integrity Poblems When Updating the Data Source Problem You sometimes get referential integrity errors when you update a DataSet that contains related parent, child, and grandchild records back to the underlying data source, but want to perform the update without errors.

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  • Data integrity refers to the consistency and accuracy of data. An important step in database planning is deciding how to ensure this integrity. Three categories of data integrity can be employed: domain, entity, and referential. Here you will learn about domain and entity integrity. (Referential integrity will be discussed in detail in the following topic.)

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  • Most algorithms dedicated to the generation of referential descriptions widely suffer from a fundamental problem: they make too strong assumptions about adjacent processing components, resulting in a limited coordination with their perceptive and linguistics data, that is, the provider for object descriptors and the lexical expression by which the chosen descriptors is ultimately realized.

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  • Power Designer là 1 công cụ thiết kế CSDL. Với Power Designer bạn có thể : Thiết kế Conceptual Data model (CDM) bằng sơ đồ thực thể kết hợp Phát sinh Physical Data Model (PDM) tương ứng trên một DBMS được chọn. Phát sinh kích bản tạo CSDL trên một DBMS đích. Phát sinh ràng buột toàn vẹn tham chiếu (referential integrity triggers) nếu chúng được hổ trợ bởi CSDL đích. Cho phép hiệu chỉnh và in các model.

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  • INDEX multidimensional arrays, 48, 56 nowdoc syntax, 54 NULL data type, 48 object data type, 48 online documentation for PHP syntax, 47 performing calculations, 49 PHP as a weakly typed language, 48 PHP quick checklist of main language points, 67 precedence of arithmetic operators, table of, 50 print_r(), using to inspect the contents of an array, 57 resource data type, 48 return keyword, 66 side-effects of PHP s weak typing, 48 single and double quotes, 52 string data type, 48 switch statement, 60 ternary operator, 61 variables inside strings, 52 while loop, 62 See also overview of PHP re...

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  • Câu 1. Giả sử có 2 bảng A và B có quan hệ 1-N với nhau, nếu muốn xóa một mẩu tin trong bảng A (bảng 1) thì Access cũng tự động xóa mẩu tin liên quan trong bảng B (bảng nhiều), trong liên kết (relationship) của 2 bảng này ta chọn: A. Cascade Delete Related Records B. Không thực hiện được yêu cầu trên C. Enforce Referential Integrity D. Cascade Update Related Fields Câu 2.

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  • Referential Integrity Values The referential integrity or FOREIGN KEY constraint is more complicated than the others we have covered so far because it relies on another table to restrict what values can be entered into the column with the referential integrity constraint. In the preceding example, a FOREIGN KEY is declared on the Customer_Number column; any values entered into this column must also exist in the Customer_Number column of another table (in this case, the CUSTOMER table).

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  • Trong trường hợp muốn thiết lập các thuộc tính đảm bảo toàn vẹn dữ liệu (Enforce Referential Integrity) cho quan hệ hãy thực hiện chọn (checked) 3 mục chọn sau: để đồng ý thiết lập các thuộc tính đảm bảo toàn vẹn dữ liệu; đảm bảo toàn vẹn dữ liệu khi xoá dữ liệu giữa 2 bảng liên quan. Khi đó, nếu một bản ghi ở bảng có quan hệ 1 bị xoá, toàn bộ các bản ghi có quan hệ với bản ghi hiện tại sẽ được tự động xoá ở bảng có quan hệ nhiều...

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  • The relational Model of Data is based on the concept of a Relation. A Relation is a mathematical concept based on the ideas of sets. The strength of the relational approach to data management comes from the formal foundation provided by the theory of relations. We review the essentials of the relational approach in this chapter.

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  • The relationships between columns in different tables are typically described through the use of keys, which are implemented through referential integrity constraints and their supporting indexes. For example, in Figure 1-2, you can establish a link between the DEPTNO column in the second table, which is called a foreign key,to the DEPTNO column in the first table, which is referred to as the primary key of that table. Finally, even if you define many different indexes for a table, you don’t have to understand them or manage the data they contain.

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  • We present a discourse-level Tree Adjoining Grammar which tightly integrates syntax and discourse levels, including a representation for discourse entities. We show that this technique makes it possible to extend an optimisation algorithm used in natural language generation (polarity filtering) to the discourse level. We implemented the grammar in a surface realizer and show that this technique can be used to reduce the search space by filtering out referentially incoherent solutions.

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  • The temporal relations that hold between events described by successive utterances are often left implicit or underspecified. We address the role of two phenomena with respect to the recovery of these relations: (1) the referential properties of tense, and (2) the role of temporal constraints imposed by coherence relations. We account for several facets of the identification of temporal relations through an integration of these.

    pdf3p bunmoc_1 20-04-2013 17 1   Download


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