SQL · Theory

Select Random Records

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Select Random Records

Don’t start Select Random Records with jargon. Start with student names. That is the whole point.

Select Random Records order — meaning → SELECT name, marks FROM … → one limit. Dumping ten features helps nobody.

Without Select Random Records, marks table gets messy and student names is hard to trust.

Select Random Records shows up in marks table. Name student names, not “a real-world scenario”.

Select Random Records trap — SELECT * in production reports. Rohit loses marks for that every viva.

After Select Random Records, Rohit should still remember SELECT * in production reports.

One breath for Select Random Records, then student names, then SELECT * in production reports. Sit down.

Diagram

  FROM students
        │
        ▼
  WHERE city = 'Pune'
        │
        ▼
  SELECT name, marks

Exam tip

Say Select Random Records in one breath, then SELECT name, marks FROM …, then SELECT * in production reports.

Select Random Records — sample query

CREATE TABLE employees (id INTEGER PRIMARY KEY, name TEXT, dept TEXT, salary INTEGER);
INSERT INTO employees VALUES
  (1, 'Asha', 'Eng', 70000),
  (2, 'Ravi', 'Eng', 65000),
  (3, 'Neha', 'HR', 50000);
SELECT name, salary FROM employees WHERE dept = 'Eng' ORDER BY salary DESC;

Select Random Records — sELECT projects columns; WHERE filters; ORDER BY sorts.

Short notes

DefSelect Random Records — Rohit uses it for student names in marks table.
RuleSelect Random Records → SELECT name, marks FROM ….
RememberSelect Random Records + InnoDB (marks table).
UseSelect Random Records in marks table (student names).
TrapSelect Random Records — SELECT * in production reports.
ExSelect Random Records → student names.

CREATE TABLE employees (id INTEGER PRIMARY KEY, name TEXT, dept TEXT, salary INTEGER); INSERT INTO employees VALUES (1, 'Asha', 'Eng', 70000), (2, 'Ravi', 'Eng', 65000), (3, 'Neha', 'HR', 50000); SELECT name, salary FROM employees WHERE dept = 'Eng' ORDER BY salary DESC;

Select Random Records

Select Random Records — sample query

Short notes

Questions

Select Random Records

Select Random Records — sample query

Short notes

Questions