---
name: query-onchain-data
description: Query onchain data on Base using the CDP SQL API via x402. Use when you or your user want to view onchain information about decoded blocks, transactions, and event.
user-invocable: true
disable-model-invocation: false
allowed-tools: ["Bash(npx awal@latest status*)", "Bash(npx awal@latest balance*)", "Bash(npx awal@latest x402 pay *)"]
---

# Query Onchain Data on Base

Use the CDP SQL API to query onchain data (events, transactions, blocks, transfers) on Base. Queries are executed via x402 and are charged per query.

## Confirm wallet is initialized and authed

```bash
npx awal@latest status
```

If the wallet is not authenticated, refer to the `authenticate-wallet` skill.

## Executing a Query

```bash
npx awal@latest x402 pay https://x402.cdp.coinbase.com/platform/v2/data/query/run -X POST -d '{"sql": "<YOUR_QUERY>"}' --json
```

**IMPORTANT**: Always single-quote the `-d` JSON string to prevent bash variable expansion.

## CRITICAL: Indexed Fields

Queries against `base.events` **MUST** filter on indexed fields to avoid full table scans. The indexed fields are:

| Indexed Field | Use For |
| --- | --- |
| `event_signature` | Filter by event type. Use this instead of `event_name` for performance. |
| `address` | Filter by contract address. |
| `block_timestamp` | Filter by time range. |

**Always include at least one indexed field in your WHERE clause.** Combining all three gives the best performance.

## CoinbaseQL Syntax

CoinbaseQL is a SQL dialect based on ClickHouse. Supported features:

- **Clauses**: SELECT (DISTINCT), FROM, WHERE, GROUP BY, ORDER BY (ASC/DESC), LIMIT, WITH (CTEs), UNION (ALL/DISTINCT)
- **Joins**: INNER, LEFT, RIGHT, FULL with ON
- **Operators**: `=`, `!=`, `<>`, `<`, `>`, `<=`, `>=`, `+`, `-`, `*`, `/`, `%`, AND, OR, NOT, BETWEEN, IN, IS NULL, LIKE
- **Expressions**: CASE/WHEN/THEN/ELSE, CAST (both `CAST()` and `::` syntax), subqueries, array/map indexing with `[]`, dot notation
- **Literals**: Array `[...]`, Map `{...}`, Tuple `(...)`
- **Functions**: Standard SQL functions, lambda functions with `->` syntax

## Available Tables

### base.events

Decoded event logs from smart contract interactions. **This is the primary table for most queries.**

| Column | Type | Description |
| --- | --- | --- |
| log_id | String | Unique log identifier |
| block_number | UInt64 | Block number |
| block_hash | FixedString(66) | Block hash |
| block_timestamp | DateTime64(3, 'UTC') | Block timestamp (**INDEXED**) |
| transaction_hash | FixedString(66) | Transaction hash |
| transaction_to | FixedString(42) | Transaction recipient |
| transaction_from | FixedString(42) | Transaction sender |
| log_index | UInt32 | Log index within block |
| address | FixedString(42) | Contract address (**INDEXED**) |
| topics | Array(FixedString(66)) | Event topics |
| event_name | LowCardinality(String) | Decoded event name |
| event_signature | LowCardinality(String) | Event signature (**INDEXED** - prefer over event_name) |
| parameters | Map(String, Variant(Bool, Int256, String, UInt256)) | Decoded event parameters |
| parameter_types | Map(String, String) | ABI types for parameters |
| action | Enum8('removed' = -1, 'added' = 1) | Added or removed (reorg) |

### base.transactions

Complete transaction data.

| Column | Type | Description |
| --- | --- | --- |
| block_number | UInt64 | Block number |
| block_hash | String | Block hash |
| transaction_hash | String | Transaction hash |
| transaction_index | UInt64 | Index in block |
| from_address | String | Sender address |
| to_address | String | Recipient address |
| value | String | Value transferred (wei) |
| gas | UInt64 | Gas limit |
| gas_price | UInt64 | Gas price |
| input | String | Input data |
| nonce | UInt64 | Sender nonce |
| type | UInt64 | Transaction type |
| max_fee_per_gas | UInt64 | EIP-1559 max fee |
| max_priority_fee_per_gas | UInt64 | EIP-1559 priority fee |
| chain_id | UInt64 | Chain ID |
| v | String | Signature v |
| r | String | Signature r |
| s | String | Signature s |
| is_system_tx | Bool | System transaction flag |
| max_fee_per_blob_gas | String | Blob gas fee |
| blob_versioned_hashes | Array(String) | Blob hashes |
| timestamp | DateTime | Block timestamp |
| action | Int8 | Added (1) or removed (-1) |

### base.blocks

Block-level metadata.

| Column | Type | Description |
| --- | --- | --- |
| block_number | UInt64 | Block number |
| block_hash | String | Block hash |
| parent_hash | String | Parent block hash |
| timestamp | DateTime | Block timestamp |
| miner | String | Block producer |
| nonce | UInt64 | Block nonce |
| sha3_uncles | String | Uncles hash |
| transactions_root | String | Transactions merkle root |
| state_root | String | State merkle root |
| receipts_root | String | Receipts merkle root |
| logs_bloom | String | Bloom filter |
| gas_limit | UInt64 | Block gas limit |
| gas_used | UInt64 | Gas used in block |
| base_fee_per_gas | UInt64 | Base fee per gas |
| total_difficulty | String | Total chain difficulty |
| size | UInt64 | Block size in bytes |
| extra_data | String | Extra data field |
| mix_hash | String | Mix hash |
| withdrawals_root | String | Withdrawals root |
| parent_beacon_block_root | String | Beacon chain parent root |
| blob_gas_used | UInt64 | Blob gas used |
| excess_blob_gas | UInt64 | Excess blob gas |
| transaction_count | UInt64 | Number of transactions |
| action | Int8 | Added (1) or removed (-1) |

## Example Queries

### Get recent USDC Transfer events with decoded parameters

```sql
SELECT
  parameters['from'] AS sender,
  parameters['to'] AS to,
  parameters['value'] AS amount,
  address AS token_address
FROM base.events
WHERE
  event_signature = 'Transfer(address,address,uint256)'
  AND address = '0x833589fcd6edb6e08f4c7c32d4f71b54bda02913'
  AND block_timestamp >= now() - INTERVAL 7 DAY
LIMIT 10
```

### Get transactions from a specific address

```bash
npx awal@latest x402 pay https://x402.cdp.coinbase.com/platform/v2/data/query/run -X POST -d '{"sql": "SELECT transaction_hash, to_address, value, gas, timestamp FROM base.transactions WHERE from_address = lower('\''0xYOUR_ADDRESS'\'') AND timestamp >= now() - INTERVAL 1 DAY LIMIT 10"}' --json
```

### Count events by type for a contract in the last hour

```bash
npx awal@latest x402 pay https://x402.cdp.coinbase.com/platform/v2/data/query/run -X POST -d '{"sql": "SELECT event_signature, count(*) as cnt FROM base.events WHERE address = lower('\''0xCONTRACT_ADDRESS'\'') AND block_timestamp >= now() - INTERVAL 1 HOUR GROUP BY event_signature ORDER BY cnt DESC LIMIT 20"}' --json
```

### Get latest block info

```bash
npx awal@latest x402 pay https://x402.cdp.coinbase.com/platform/v2/data/query/run -X POST -d '{"sql": "SELECT block_number, timestamp, transaction_count, gas_used FROM base.blocks ORDER BY block_number DESC LIMIT 1"}' --json
```

## Common Contract Addresses (Base)

| Token | Address |
| --- | --- |
| USDC | `0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913` |
| WETH | `0x4200000000000000000000000000000000000006` |

## Best Practices

1. **Always filter on indexed fields** (`event_signature`, `address`, `block_timestamp`) in `base.events` queries.
2. **Never use `SELECT *`** - specify only the columns you need.
3. **Always include a `LIMIT`** clause to bound result size.
4. **Use `event_signature` instead of `event_name`** for filtering - it is indexed and much faster.
5. **Use time-bounded queries** with `block_timestamp` to narrow the scan range.
6. **Always wrap address values in `lower()`** - the database stores lowercase addresses but users may provide checksummed (mixed-case) addresses. Use `address = lower('0xAbC...')` not `address = '0xAbC...'`.
7. **Common event signatures**: `Transfer(address,address,uint256)`, `Approval(address,address,uint256)`, `Swap(address,uint256,uint256,uint256,uint256,address)`.

## Prerequisites

- Must be authenticated (`npx awal@latest status` to check, see `authenticate-wallet` skill)
- Wallet must have sufficient USDC balance (`npx awal@latest balance` to check)
- Each query costs $0.10 (100000 USDC atomic units)

## Error Handling

- "Not authenticated" - Run `awal auth login <email>` first, or see `authenticate-wallet` skill
- "Insufficient balance" - Fund wallet with USDC; see `fund` skill
- Query timeout or error - Ensure you are filtering on indexed fields and using a LIMIT