How Can SQL Determine Data Equivalence Between Two Structurally Identical Tables?

SQL: Identifying Data Equivalency Between Two Tables

Question:

Amidst the labyrinthine world of data storage, two tables, TableA and TableB, mirror each other in structure, sharing identical columns labeled A, B, C, D, E, and F. TableA and TableB reign as guardians of these columns, safeguarding their primary key secrets within A and B.

How can you harness the power of SQL to determine if TableA and TableB house the exact same treasure trove of data, down to the finest detail hidden within each column? By unravelling this data equivalence enigma, you'll gain a crystal-clear understanding of the harmony or disparities that lie within these tabular realms.

Answer:

To embark on this mission, consider the concept of "set operations in SQL." These operations allow you to manipulate and compare sets of data. Among them, two stand out: "MINUS" and "EXCEPT." Your choice of operator depends on the flavor of SQL your DBMS favors.

To unleash the power of these operators, craft a query that pits TableA against TableB. Here's a sample spell:

select * from tableA
minus
select * from tableB

Prepare yourself for a truth-revealing moment. If this query remains silent, returning not a single row, then rejoice! It's a testament to the perfect alignment of data within TableA and TableB. They are truly one and the same in content.

Should this query unveil a populated result set, however, know that TableA and TableB have diverged. They possess distinct data elements, setting them apart in the vast expanse of the data universe.

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