# json_agg

Collect group inputs, including NULL, into a JSON array.

**Syntax**

```text
json_agg(value)
```

**Arguments**

One SQL expression per row, converted to a JSON value. FILTER, DISTINCT, ordering and windows are supported.

**Returned value**

JSON-tagged TEXT array, or NULL when no input row exists.

**Examples**

```sql
CREATE TABLE readings (value INTEGER);
INSERT INTO readings VALUES (1),(NULL),(2);
```

```sql
SELECT json_agg(value) FROM readings FORMAT csv;
```

```text
"[1,null,2]"
```