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Left Join vs Right Join

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Left Join vs Right Join

Left Join vs Right Join sits in a report. Neha’s job is student + marks. Write that first.

Do Left Join vs Right Join once by hand. JOIN … ON s.roll = m.roll. Change one input. Say the new result out loud.

Left Join vs Right Join exists so Neha can keep student + marks correct in a report.

Neha ships Left Join vs Right Join in a report. That is the use case worth saying.

Left Join vs Right Join miss — missing ON → cartesian product. Fix it before you talk about advanced SQL.

Place Left Join vs Right Join next to nearby SQL work — JOIN … ON s.roll = m.roll is the link.

Viva for Left Join vs Right Join: what it is → JOIN … ON s.roll = m.roll → the mistake (missing ON → cartesian product).

Diagram

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

Exam tip

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

Left Join vs 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;

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

Short notes

DefLeft Join vs Right Join — Neha uses it for student + marks in a report.
RuleLeft Join vs Right Join → JOIN … ON s.roll = m.roll.
RememberLeft Join vs Right Join + the query planner (a report).
UseLeft Join vs Right Join in a report (student + marks).
TrapLeft Join vs Right Join — missing ON → cartesian product.
ExLeft Join vs Right 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;

Left Join vs Right Join

Left Join vs Right Join — sample query

Short notes

Questions

Left Join vs Right Join

Left Join vs Right Join — sample query

Short notes

Questions