Fix variable naming

The variable should better reflect what the query is doing.

project1/a.sql

@@ -102,8 +102,8 @@ WHERE sig_id <> pk_id;
 -- #16.1.5 Get blocks with inputs that have outputs which have already been
 -- spent (double-spending)
 
--- First, get outputs that have been doubly spent
-CREATE OR REPLACE VIEW outputs_doubly_spent AS (
+-- First, get outputs that have more than one input
+CREATE OR REPLACE VIEW outputs_multiple_inputs AS (
     SELECT output_id
     FROM non_coinbase_inputs
     JOIN outputs USING(output_id)
@@ -113,14 +113,14 @@ CREATE OR REPLACE VIEW outputs_doubly_spent AS (
 -- Second, get corresponding input_id where the output was first spent
 CREATE OR REPLACE VIEW inputs_first_spent AS (
     SELECT MIN(input_id) AS input_id, output_id
-    FROM outputs_doubly_spent
+    FROM outputs_multiple_inputs
     JOIN non_coinbase_inputs USING(output_id)
     GROUP BY output_id
 );
 -- Third, combine to get invalid blocks
 INSERT INTO temporary_table
 SELECT block_id
-FROM outputs_doubly_spent
+FROM outputs_multiple_inputs
 JOIN non_coinbase_inputs USING(output_id)
 WHERE input_id NOT IN (
     SELECT input_id