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EXPLAIN

Returns the query execution plan for a specified query statement without running it. EXPLAIN can help you identify opportunities to tune query performance before you run a query.

By default, EXPLAIN returns output in JSON format.The SQL workspace uses the JSON to generate visual explain output. For more information, including example JSON output, see Using explain to analyze query execution. Specify the USING TEXT option to return plain text.

Syntax 

EXPLAIN [USING {TEXT|JSON}] <query_statement>
Parameter Description
[USING {TEXT|JSON}] Specifies the output format for the query plan. Defaults to JSON if not specified. If USING TEXT is specified, list view and graph view are not available. For more information, see Viewing and copying explain output.
<query_statement> Any query statement that does not include DDL commands.

Example

The example below demonstrates an EXPLAIN statement for a SELECT query on a table named lineitem.

EXPLAIN
SELECT
	l_shipdate,
	l_linestatus,
	l_orderkey,
	AVG(l_discount)
FROM
	lineitem
WHERE
	l_returnflag = 'N'
	AND l_shipdate > '1996-01-01'
GROUP BY
	l_shipdate,
	l_linestatus,
	l_orderkey
ORDER BY
	1,2,3,4;

Returns:

The EXPLAIN results indicate that this SELECT query will execute operations as follows. The Firebolt engine will:

  1. Filter the lineitem table for columns used in the SELECT query, and then by the WHERE conditions.
  2. Perform the aggregation as specified by the GROUP BY clause.
  3. Sort results in ascending order by the l_shipdate column, as specified by the ORDER BY clause.