Fetch query
In this guide, you’ll see how to retrieve data from a database and project it as a JSON using Studio, Console, or one of the drivers.
Understanding Fetch queries
A Fetch query is used to retrieve values and types from a TypeDB database. For a detailed explanation of the query see the Fetch query page.
Sending Fetch queries
Before getting start, ensure you followed instructions from the Writing data section. The easiest way to send a Fetch query is to use Studio or Console:
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Studio
-
Console
Follow the Studio manual to connect to TypeDB and select a project folder. Then use the steps below:
-
Use a drop-down list in the top toolbar to select a database.
-
Switch to
datasession andreadtransaction types. -
Open a new tab and insert or type in an Insert query, for example:
TypeQL Fetch querymatch $u isa user; fetch $u: name, email; -
Run the query by clicking the
Run Query button.
-
Open a
datasession andreadtransaction to the selected database (e.g.,sample_db):transaction sample_db data read -
Send the Fetch query:
match $u isa user; fetch $u: name, email;Push Enter twice to send the query.
-
Close the transaction:
close
The resulted JSONs should look like this:
{
"u": {
"email": [ { "value": "alice@typedb.com", "type": { "label": "email", "root": "attribute", "value_type": "string" } } ],
"name": [ { "value": "Alice", "type": { "label": "name", "root": "attribute", "value_type": "string" } } ],
"type": { "label": "user", "root": "entity" }
}
}
{
"u": {
"email": [ { "value": "the-bob@typedb.com", "type": { "label": "email", "root": "attribute", "value_type": "string" } } ],
"name": [ { "value": "Bob", "type": { "label": "name", "root": "attribute", "value_type": "string" } } ],
"type": { "label": "user", "root": "entity" }
}
}
{
"u": {
"email": [ { "value": "charlie@typedb.com", "type": { "label": "email", "root": "attribute", "value_type": "string" } } ],
"name": [ { "value": "Charlie", "type": { "label": "name", "root": "attribute", "value_type": "string" } } ],
"type": { "label": "user", "root": "entity" }
}
}To send a Fetch query programmatically, use drivers:
-
Rust
-
Python
-
Node.js
-
Java
-
C#
-
C++
-
C
Follow the connection guide
to connect the driver to a TypeDB server.
let databases = DatabaseManager::new(driver);
let db = databases.get(DB_NAME)?;
{
let session = Session::new(db, SessionType::Data)?;
{
let tx = session.transaction(TransactionType::Read)?;
let fetch_query = "
match
$u isa user;
fetch
$u: name, email;
";
let response = tx.query().fetch(fetch_query)?;
for (i, json) in response.enumerate() {
println!("User #{}: {}", (i + 1).to_string(), json.unwrap().to_string())
}
}
}Follow the connection guide
to connect the driver to a TypeDB server.
with driver.session(DB_NAME, SessionType.DATA) as session:
with session.transaction(TransactionType.READ) as tx:
fetch_query = """
match
$u isa user;
fetch
$u: name, email;
"""
response = tx.query.fetch(fetch_query)
for i, JSON in enumerate(response, start=1):
print(f"User #{i}: {JSON}")Follow the connection guide
to connect the driver to a TypeDB server.
try {
session = await driver.session(DB_NAME, SessionType.DATA);
try {
tx = await session.transaction(TransactionType.READ);
const fetch_query = `
match
$u isa user;
fetch
$u: name, email;
`;
let response = await tx.query.fetch(fetch_query).collect();
for (let i = 0; i < response.length; i++) {
console.log("User #" + (i + 1) + ": " + JSON.stringify(response[i], null, 4));
}
}
finally {if (tx.isOpen()) {await tx.close()};}
}
finally {await session?.close();}Follow the connection guide
to connect the driver to a TypeDB server.
try (TypeDBSession session = driver.session(DB_NAME, TypeDBSession.Type.DATA)) {
try (TypeDBTransaction tx = session.transaction(TypeDBTransaction.Type.READ)) {
String fetchQuery = """
match
$u isa user;
fetch
$u: name, email;
""";
int[] ctr = new int[1];
tx.query().fetch(fetchQuery).forEach(result -> System.out.println("Email #" + (++ctr[0]) + ": " + result.toString()));
}
}Follow the connection guide
to connect the driver to a TypeDB server.
using (ITypeDBSession session = driver.Session(DB_NAME, SessionType.Data)) {
using (ITypeDBTransaction tx = session.Transaction(TransactionType.Read)) {
string fetch_query = @"
match
$u isa user;
fetch
$u: name, email;";
List<JObject> response = tx.Query.Fetch(fetch_query).ToList();
foreach (JObject answer in response) {
Console.WriteLine("User: " + answer.ToString());
}
}
}Follow the connection guide
to connect the driver to a TypeDB server.
TypeDB::Options options;
TypeDB::Session session = driver.session(DB_NAME, TypeDB::SessionType::DATA, options);
{
TypeDB::Transaction tx = session.transaction(TypeDB::TransactionType::READ, options);
std::string fetchQuery = R"(
match
$u isa user;
fetch
$u: name, email;
)";
TypeDB::JSONIterable results = tx.query.fetch(fetchQuery);
std::vector<TypeDB::JSON> fetchResult;
for (TypeDB::JSON& result : results) {
fetchResult.push_back(result);
}
}Follow the connection guide
to connect the driver to a TypeDB server.
Options* opts = options_new();
session = session_new(databaseManager, DB_NAME, Data, opts);
tx = transaction_new(session, Read, opts);
if ((tx == NULL) || FAILED()) {
handle_error("Transaction failed to start.");
goto cleanup;
}
char query[512];
snprintf(query, sizeof(query), "match $u isa user; fetch $u: name, email;");
StringIterator* users = query_fetch(tx, query, opts);
if (FAILED()) {
handle_error("Query execution failed.");
goto cleanup;
}
char *userJSON;
while ((userJSON = string_iterator_next(users)) != NULL) {
printf("%s %s\n", "User:", userJSON);
}
transaction_close(tx);
session_close(session);Response interpretation
A Fetch query returns all fetched values projected in JSON objects.
The response is a Stream/Iterator with a JSON object for every solution of a match clause pattern.
A concept can’t be returned directly, but a value or a type can be projected into the resulting JSON.
To return full concepts, see the Get query page.