NullExpression

The NullExpression is part of the Dynamic Where feature; it represents a NULL value.

Implementation

Example

Target SQL where clause:

WHERE client_address IS NULL

 

WhereExpression where = new BinaryExpression(
                          new FieldExpression("CLIENTS", "Client_Address"),
                          new NullExpression(),
                          BinaryOperator.Equal);

 

let whereExpression = BinaryExpression(
            FieldExpression("CLIENTS", "Client_Address"),
            NullExpression(),
            BinaryOperator.Equal)

 

WhereExpression where = new BinaryExpression(
                            new FieldExpression("CLIENTS", "Client_Address"),
                            new NullExpression(),
                            BinaryOperator.Equal);

 

let whereExpression = BinaryExpression(
            FieldExpression("CLIENTS", "Client_Address"),
            NullExpression(),
            BinaryOperator.Equal)

 

with ClientDataModule.tbl_CLIENTS,DynamicWhere do begin
   Expression:=NewBinaryExpression(
                 NewField(LogicalName,'Client_Address'),
                 NewNull(),
                 dboEqual);
end;

 

myTable.dynamicWhere = new RemObjects.DataAbstract.DynamicWhere(
        new RemObjects.DataAbstract.BinaryExpression(
          new RemObjects.DataAbstract.FieldExpression("Client_Address"),
          new RemObjects.DataAbstract.NullExpression(), "Equal")
        ));

Generated XML/JSON

<?xml version="1.0"?>
<query xmlns="http://www.remobjects.com/schemas/dataabstract/queries/5.0" version="5.0">
  <where>
    <binaryoperation operator="Equal">
      <field tablename="CLIENTS">Client_Address</field>
      <null/>
    </binaryoperation>
  </where>
</query>

{
  "type": "query.where",
  "expression": {
    "type": "binaryoperation",
    "left": {
      "type": "field",
      "field": "Client_Address",
      "table": "CLIENTS"
    },
    "operator": "Equal",
    "right": {
      "type": "null"
    }
  }
}