count unique values in a table

... Typed DataSet Problem When a column in a database has a null value, you want the value in the DataSet to be a string indicating that no value is available. Solution Use annotations in the ... the default or annotated schema file is used. In either case, data is loaded into the DataSet. A row is added to the Categories table with a Description value of null. The data in the table is ... Description values are replaced with the string "- no description available -". The annotations are marked in bold in Example 2-25 . Example 2-25. File: TypedDataSets\CategoriesDS_AnnotatedNull.xsd...

Ngày tải lên: 14/12/2013, 18:16

... of lblSQLString. Then the string is used in a data adapter that was created to fill the dtResults data table. Last, the data table is set as the data source for dgResults. Listing 6.7 frmHowTo6_3.vb: ... placing your use of wild cards and allowing for ranges of values, you can make your applications and the querying of data more versatile than ever! Label Text To TextBox Name txtFromDate ... MyBase.Load GenerateData() End Sub 3. In the class module for the form, add the code in Listing 6.7 to create the GenerateData routine. After creating the SQL statement, this routine assigns...

Ngày tải lên: 14/12/2013, 20:16

... don't have corresponding records (invoices) in a related table, you have to have a better understanding of the types of joins that can be used between tables during queries. Before looking ... records in which at least one record exists in each table for the joined field. This means that customers are displayed only if they have at least one invoice. If you want to see the CompanyName and ... of Joins You can use three types of joins to bring back different information. These join types include inner joins, left outer joins, and right outer joins. Inner Join This join displays...

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Ngày tải lên: 07/08/2014, 06:20

... area, Years and Date are in the Row Labels area, and Units is in the Values area. If you calculate a running total with Date as the base field: • The subtotals for Years are automatically hidden ... each sales manager. In your pivot table, Sales Manager is in the Row Labels area, Category is in the Column Labels area, and Units is in the Values area (see the table at the left in Figure 3-18). ... cells. CHAPTER 3 ■ CALCULATIONS IN A PIVOT TABLE 45 Calculations in a Pivot Table I n a pivot table, you can use functions like Sum, Count, or Average to summarize the fields you place in the Values...

Ngày tải lên: 09/10/2013, 12:20

... Create DataAdapter. SqlDataAdapter da = new SqlDataAdapter(sqlText, conn); // Add table mappings. da.TableMappings.Add(" ;Table& quot;, "Orders"); da.TableMappings.Add(" ;Table1 ", ... collection in the DataSet. foreach(DataTable dt in ds.Tables) { schemaInfo.Append(" ;TABLE: " + dt.TableName + Environment.NewLine); // Create the command to retrieve column information. ... Server Books Online. The GetSchemaTable( ) method of the DataReader also returns all column lengths. The method returns a DataTable containing column metadata for a DataReader, where the ColumnSize...

Ngày tải lên: 24/12/2013, 05:15

... Table in the Database from a DataTable Schema Problem You need to create a table in a database from an existing DataTable schema. Solution Use the CreateTableFromSchema( ) method shown in this ... CreateTableFromSchema( ) in the sample code is called to create a table in the database from this schema. CreateTableFromSchema( ) This method creates a schema in the database for the schema of the DataTable ... dynamically constructs a Data Definition Language (DDL) statement to create a table in a SQL Server database from the schema of a DataTable. The complete statement that is generated is shown in...

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... the main program is busy doing something, the other threads can handle the user inputs and perform the tasks. For example, if a user wants to cancel bringing in a large amount of data from a web ... threads to handle individual tasks. For instance, if a thread performing activity A spends a significant amount of time waiting for an I/O operation to complete, another thread can be created ... pressing a button or constantly interacting with the program, are independent activities. The performance of an application can be improved by creating a separate thread for performing each of...

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... critically ill patients in emergency situations. As part of their HEMS training programme, intraosseous training was given using man- ual needles, Bone Injection Guns, and EZ-IO® on both manikins and ... Heltne 1,2,3 Abstract Background: Intraosseous access (IO) is a method for providing vascular access in out-of-hospital resuscitation of critically ill and injured patients when traditional intravenous access ... Newer intraosseous techniques may enable faster and more reliable vascular access, and this can lower the threshold for intraosseous access on both adult and paediatric patients in critical situations....

Ngày tải lên: 25/10/2012, 10:02