This rewrite converts ANSI‑style inner join syntax to comma‑style syntax if the entire query is based on inner joins. For example, consider the following query:
SELECT *
FROM t1
INNER JOIN t2 ON a1=a2
INNER JOIN t3 ON a2=a3;
This query is converted to the following form by the rewrite:
SELECT *
FROM t1,t2,t3
WHERE a1=a2
AND a2=a3;