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READ Function (Query)

  • Artigo

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

The following code shows the syntax of the READ function. Query is a variable of the Query data type that specifies the query object.

Syntax

[Ok :=] Query.READ

Return Value

Type: Boolean

true if a row in the resulting dataset was retrieved; otherwise, false.

Remarks

When the READ function 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 function before the READ function. After the READ function call, columns can be accessed as shown in the following code example.

query.OPEN;  
query.READ;  
query.ColumnName

You can call the READ function multiple times after the OPEN function to read consecutive rows in the dataset. The first READ function call retrieves the first row from the resulting dataset and each subsequent READ function retrieves the next row from the dataset. For example, the second READ function call retrieves the second row, the third READ function 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 function is called and there are no more rows in the dataset, then the READ function returns false.

Example

The following example demonstrates how to use the READ function 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 do the following:

  • 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.

    For step-by-step instructions for creating this query, see Walkthrough: Creating a Query to Link Two Tables.

  • Create the following variable and text constant.

    Variable name DataType Subtype
    MyQuery Query Customer_SalesQuantity
    Text constant name ENU Value
    Text000 Customer name = %1, Quantity = %2

    The following C/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.

// 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;