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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* Content before git sha 34fdeebefcbf183ed7f916f931aa0586fdaa1b40
* Copyright (c) 2016, The Gocql authors,
* provided under the BSD-3-Clause License.
* See the NOTICE file distributed with this work for additional information.
*/
package gocql_test
import (
"fmt"
"log"
gocql "github.com/gocql/gocql"
)
// Example_nulls demonstrates how to distinguish between null and zero value when needed.
//
// Null values are unmarshalled as zero value of the type. If you need to distinguish for example between text
// column being null and empty string, you can unmarshal into *string field.
func Example_nulls() {
/* The example assumes the following CQL was used to setup the keyspace:
create keyspace example with replication = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 };
create table example.stringvals(id int, value text, PRIMARY KEY(id));
insert into example.stringvals (id, value) values (1, null);
insert into example.stringvals (id, value) values (2, '');
insert into example.stringvals (id, value) values (3, 'hello');
*/
cluster := gocql.NewCluster("localhost:9042")
cluster.Keyspace = "example"
session, err := cluster.CreateSession()
if err != nil {
log.Fatal(err)
}
defer session.Close()
scanner := session.Query(`SELECT id, value FROM stringvals`).Iter().Scanner()
for scanner.Next() {
var (
id int32
val *string
)
err := scanner.Scan(&id, &val)
if err != nil {
log.Fatal(err)
}
if val != nil {
fmt.Printf("Row %d is %q\n", id, *val)
} else {
fmt.Printf("Row %d is null\n", id)
}
}
err = scanner.Err()
if err != nil {
log.Fatal(err)
}
// Row 1 is null
// Row 2 is ""
// Row 3 is "hello"
}
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