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Right Join

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Right Join

Right Join is simple if you keep it on paper. Amit uses it for student + marks in a report.

For Right Join, InnoDB is in play. Don’t blame it until you have traced student + marks.

Right Join exists so Amit can keep student + marks correct in a report.

Right Join shows up in a report. Name student + marks, not “a real-world scenario”.

Don’t do this with Right Join — missing ON → cartesian product. Interviewers spot it in ten seconds.

After Right Join, Amit should still remember missing ON → cartesian product.

One breath for Right Join, then student + marks, then missing ON → cartesian product. Sit down.

Diagram

  students.id
       =
  marks.student_id
        │
        ▼
     one result row

Exam tip

Say Right Join in one breath, then JOIN … ON s.roll = m.roll, then missing ON → cartesian product.

Right Join — sample query

CREATE TABLE customers (id INTEGER PRIMARY KEY, name TEXT);
CREATE TABLE orders (id INTEGER PRIMARY KEY, customer_id INTEGER, total INTEGER);
INSERT INTO customers VALUES (1, 'Asha'), (2, 'Ravi');
INSERT INTO orders VALUES (10, 1, 500), (11, 1, 200);
SELECT c.name, o.total
FROM customers c
JOIN orders o ON o.customer_id = c.id;

Right Join — jOIN combines rows using a match condition between tables.

Short notes

DefRight Join — Amit uses it for student + marks in a report.
RuleRight Join → JOIN … ON s.roll = m.roll.
RememberRight Join + InnoDB (a report).
UseRight Join in a report (student + marks).
TrapRight Join — missing ON → cartesian product.
ExRight Join → student + marks.

CREATE TABLE customers (id INTEGER PRIMARY KEY, name TEXT); CREATE TABLE orders (id INTEGER PRIMARY KEY, customer_id INTEGER, total INTEGER); INSERT INTO customers VALUES (1, 'Asha'), (2, 'Ravi'); INSERT INTO orders VALUES (10, 1, 500), (11, 1, 200); SELECT c.name, o.total FROM customers c JOIN orders o ON o.customer_id = c.id;

Right Join

Right Join — sample query

Short notes

Questions

Right Join

Right Join — sample query

Short notes

Questions