SQL · Theory

Select Database

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Select Database

Sara only reaches for Select Database when student names has to stay correct in marks table.

Keep Select Database small. Sara should finish student names in a few lines, not a 40-line dump.

Skip Select Database and SELECT * in production reports shows up in marks table.

Sara ships Select Database in marks table. That is the use case worth saying.

Select Database miss — SELECT * in production reports. Fix it before you talk about advanced SQL.

Place Select Database next to nearby SQL work — SELECT name, marks FROM … is the link.

Viva for Select Database — what it is → SELECT name, marks FROM … → the mistake (SELECT * in production reports).

Diagram

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

Exam tip

For Select Database: definition + marks table + one failure.

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

Short notes

DefSelect Database — Sara uses it for student names in marks table.
RuleSelect Database → SELECT name, marks FROM ….
RememberSelect Database + the query planner (marks table).
UseSelect Database in marks table (student names).
TrapSelect Database — SELECT * in production reports.
ExSelect Database → 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 Database

Select Database — sample query

Short notes

Questions

Select Database

Select Database — sample query

Short notes

Questions