Query.Read() Method

Artikkel
05/14/2024

Version: Available or changed with runtime version 1.0.

Reads data from a row in the resulting data set of a query.

Syntax

[Ok := ]  Query.Read()

Parameters

Query
Type: Query
An instance of the Query data type.

Return Value

[Optional] Ok
Type: Boolean
true if the operation was successful; otherwise false. If you omit this optional return value and the operation does not execute successfully, a runtime error will occur.

Remarks

When the Read method is called, the next row in the dataset query is retrieved. While in the reading state, values of columns in the row can be accessed by calling Query.ColumnName, where Query is the query type variable that specifies the query object and ColumnName is the column of the query.

To read a row in the dataset, you must call the Open method before the Read method. After the Read method call, columns can be accessed as shown in the following code example.

query.Open;  
query.Read;  
query.ColumnName

You can call the Read method multiple times after the Open method to read consecutive rows in the dataset. The first Read method call retrieves the first row from the resulting dataset and each subsequent Read method retrieves the next row from the dataset. For example, the second Read method call retrieves the second row, the third Read method call retrieves the third row, and so on.

Query.Open;  
// Reads the first row in the dataset.  
Query.Read;   
// Accesses a column in the first row of the dataset.  
Query.ColumnName  
// Reads the second row in the dataset.  
Query.Read;   
// Accesses a column in the first row of the dataset.  
Query.ColumnName

Note

If the Read method is called and there are no more rows in the dataset, then the Read method returns false.

Example

The following example demonstrates how to use the Read method on a query. The example code sets filters on the query, opens the query, and then reads the dataset. For each row in the dataset, a message box is displayed that contains the values of the columns in the row.

This example requires that you create a query called Customer_SalesQuantity that is links table 18 Customer with table 37 Sales Lines from the CRONUS International Ltd. demonstration database. Include columns for the Name and No. fields from the Customer table and the Quantity field from Sales Lines table.

The following AL code opens the query, reads each row of dataset, and then displays a message that has the content of the row. You can add the code to a codeunit, and then run the codeunit to see the results.

var
  MyQuery: Query "Customer SalesQuantity";
  Text000: Label 'Customer name = %1, Quantity = %2'; 
begin
    // Sets a filter to display only sales quantities greater than 20.  
    MyQuery.SetFilter(Quantity, '>20');   
    // Runs the query.  
    MyQuery.Open;  
    // Reads each row in the dataset and displays message with column values.  
    // Stops reading when there are no more rows remaining in the dataset (Read is False).  
    while MyQuery.Read do  
    begin  
      Message(Text000, MyQuery.Name, MyQuery.Quantity);   
    end;  
    // Closes the query.  
    MyQuery.Close;  
end;

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