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Querying Basics

This guide covers the fundamentals of querying data in Fluree.

Query Structure​

A Fluree query has three main parts:


{
"from": "my-ledger",
"select": "...",
"where": "..."
}

  • from: The ledger to query
  • where: Patterns to match (what data to find)
  • select: What to return (how to format results)

Selecting a Specific Entity​

To get all properties of a known entity:


{
"from": "my-ledger",
"select": {"ex:alice": ["*"]}
}

The * means "all properties."

Selecting Specific Properties​

Request only the properties you need:


{
"from": "my-ledger",
"select": {"ex:alice": ["name", "email", "department"]}
}

Finding Entities by Pattern​

Use where with logic variables (prefixed with ?) to find entities:


{
"from": "my-ledger",
"where": {
"@id": "?person",
"@type": "Person"
},
"select": {"?person": ["name", "email"]}
}

This finds all entities of type Person and returns their name and email.

Logic Variables​

Variables like ?person act as placeholders that Fluree fills in with matching values:


{
"from": "my-ledger",
"where": {
"@id": "?person",
"department": "Engineering"
},
"select": "?person"
}

Returns IDs of everyone in Engineering.

Filtering Results​

Add conditions to your where clause:


{
"from": "my-ledger",
"where": [
{"@id": "?person", "age": "?age"},
["filter", "(> ?age 30)"]
],
"select": {"?person": ["name", "age"]}
}

Traversing Relationships​

Navigate through entity references:


{
"from": "my-ledger",
"select": {"ex:alice": ["name", {"worksAt": ["name", "industry"]}]}
}

This returns Alice's name and her company's name and industry.

Result Formats​

Single value:


"select": "?name"

Array of values:


"select": ["?name", "?email"]

Entity with properties:


"select": {"?person": ["name", "email"]}

Next Steps​