hautelook orders

We use examples to illustrate this partTable structureNow has the Customer table, the order form, the Book table, the author table, Client table customer (ID customer_name) Orders form order (ID order_name customer_id book_id) Book table (ID book_name author_id) Author table (ID author_name) Model definitionThe following is the definition of these 4 models, which only write out the associationsCustomerClass Customer extends \

When querying a data component, You need to convert the dataset into an object set. The results you see during the test are a bit unexpected. datareder fills in the object set ratio dataadapter. the efficiency of filling fill into dataset is high! Dataadapter. the internal working principle of fill is not understood, but the object set is strongly typed in the case of data conversion, while dataset is not a strong type. The principle is that filling dataset is superior in efficiency, the test re

next query. Note: You can place the columns that are frequently returned in the include column of the index, and overwrite as many columns as possible without increasing the index key size. In this way, when you encounter certain queries, when you do not use the pilot column of the composite index, but do not feel it is worthwhile to create an index for it, if the field used for this query is indexed by the composite index, you can perform a non-clustered index scan to complete the query (Whe

Turn to an article that thinks it is okay MTO (make to order), that is, for order production. This production mode is used with MTS (make to stock), Ato (assembly to order, for order assembly) together with ETO (engineering to order, order-oriented design), it is a common production model in enterprises. The MTO production model has the following main features: 1. There are many product categories. Because orders are produced by a single order, and th

query optimizer selects the execution T-SQL statement and includes the sequence of steps and the type of operation in use. Data access method is an object that describes how database objects (such as data tables and indexes) are accessed. These two are related because sometimes data access methods are considered part of the Execution Plan. Of course, you can also consider it separately.________________________________________The following describes a complex example of using query analyzer. Exa

pre-process the constraint.5. Use T-SQL statements to create a trigger The basic statement is as follows ﹕Create trigger trigger_nameOn {table_name | view_name}{For | after | instead}[Insert, update, delete]AsSQL _statement 6. delete a trigger: The basic statement is as follows ﹕ Drop trigger trigger_name 7. view existing triggers in the database: -- View existing triggers in the databaseUse jxcsoftwareGoSelect * From sysobjects where xtype = 'tr' -- View a single triggerExec sp_helptext 'trigg

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: Select ... where...column in or not in or between and @parameter 4. Logical predicate: Select ... One predicate or, and other predicates or, and more predicates .... We analyze in turn the above several cases, how to use the Index for query optimization First, dynamic index lookup The so-called Dynamic index lookup is SQL Server in the execution of the statement, only to format the query criteria, and then according to the different query conditions automatically match the index entries, to ac

mainly divided into three types: Entity Integrity) Specifies that a row (that is, each record) of a table is a unique entity in the table. Entity integrity is achieved through the primary key of the table. Domain Integrity) The columns (fields) in the database table must comply with certain data types or constraints. Such as not null. Referential Integrity) Make sure that the foreign key of one table corresponds to the primary key of the other table. DDL data definition language Defin

, logic read 1724 times should return 1724 data bar, a little dizzy, here to explain The next logical reading refers to the number of pages read, a face 8kb,8 a page to form a district 64KB, for our example table 22 pages enough to save all the data, so the table scan only read 22 times on it, That query 4.5 Why read 1724 times, even if a page on a piece of data logically say up to 800 times can also read, this is because SQL Server to read the smallest unit of data is the page, even read a piec

Third week of August 8, 2001 a.1997 customers who have business dealings with the company in the year The so-called business dealings is to have sales relationship with the enterprise, whether there is a sales relationship can be obtained from the Orders table, so it is easy to think of using Word query technology to solve the problem. We can get a sales relationship customer number through the following query: SELECT

... One predicate or, and other predicates or, and more predicates .... We analyze in turn the above several cases, how to use the Index for query optimization First, dynamic index lookup The so-called Dynamic index lookup is SQL Server in the execution of the statement, only to format the query criteria, and then according to the different query conditions automatically match the index entries, to achieve performance improvement purposes. To give an example. SET showplan_text on GO SELECT Orde

Sub-query:subqueries, which are queries nested within other queries. For example, we have such a few tables, customer tables, order forms, commodity tables, we want to know which customers have bought a product, then we need to check which orders are included in the product A, and then according to the order to find out which customers.Mysql> Select cust_id from Orders where Order_num in (select Order_num f

Tags: how many bit src OSI Arc Group _id solution nalSQL row-to-column and column-changing careersThe ranks of each other, is a frequently encountered demand. The implementation method is implemented with case-when mode and a built-in pivot and Unpivot method after 2005. After reading the technical Insider's section, although these solutions have long been used, but there is no systematic understanding and summed up. In order to deepen the understanding, summarize once more. Rows and columns can

in actual development, we often query or count subtable information, it is still relatively simple to process a layer. If the Layer 2, Layer 3, or more, the written conditions are complicated and prone to write errors. SQL artisan In addition to flexible comparison functions, the Field object , Object in method also provides n layer condition nesting function, it makes it more flexible to construct query conditions. ToMSSQLOfNorthwindFor example: Query the sales amount of a sp