SQL · Theory

DROP Table

Theory

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DROP Table

DROP TABLE students; removes the table and its data. DROP TABLE IF EXISTS students; is the script form. Child tables with FOREIGN KEY to students must be dropped first or FKs removed.

Trap — DROP TABLE when you meant DELETE FROM. Trap: dropping in the wrong database.

On the example next to this theory: DROP Table: create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Exam tip

DROP TABLE IF EXISTS students; — structure and data both go.

DROP Table — sample query

-- DROP Table
CREATE TABLE demo (
  id INTEGER PRIMARY KEY,
  label TEXT NOT NULL,
  qty INTEGER DEFAULT 0
);
INSERT INTO demo (id, label, qty) VALUES
  (1, 'alpha', 2),
  (2, 'beta', 5);
SELECT label, qty FROM demo WHERE qty >= 2 ORDER BY qty DESC;

DROP Table: create two demo rows, then SELECT qty >= 2 ordered. Say which labels come back.

Short notes

DefDROP TABLE removes the table completely.
RuleIF EXISTS in scripts. Check FKs first.
TrapDROP instead of DELETE.

-- DROP Table CREATE TABLE demo ( id INTEGER PRIMARY KEY, label TEXT NOT NULL, qty INTEGER DEFAULT 0 ); INSERT INTO demo (id, label, qty) VALUES (1, 'alpha', 2), (2, 'beta', 5); SELECT label, qty FROM demo WHERE qty >= 2 ORDER BY qty DESC;

DROP Table

DROP Table — sample query

Short notes

Questions

DROP Table

DROP Table — sample query

Short notes

Questions