SQLazy：Merge Multiple Tables into Single Rows by Common ID

Problem Description Merge multiple structurally similar tables with different column names into a wide table using full outer joins by common ID. Four tables have similar structures, each with two fields. The fields have the same meaning but different names (id, id2, id3, id4 all represent ID). The goal is to merge the four tables into single rows by ID, with each ID appearing in exactly one row. When an ID is absent in a table, the corresponding columns take NULL. Source Data T1 table: T2 table: T3 table: T4 table: *Expected Result * For example, ID=555 appears in both T1 and T2 but not in T3 or T4, so id, colA, id2, colB have values, while id3/colC/id4/colD are NULL. ID=222 only appears in T3, so only id3 and colC have values; all other columns are NULL. ID=10 appears in T2 and T4 but not in T1 or T3, so id2, colB, id4, colD have values; all other columns are NULL. SQLazy Step-by-Step Implementation Core Idea: First use derive to unify the ID co