SQL · Theory

Show Columns

Theory

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Show Columns

SHOW COLUMNS FROM students; is DESCRIBE in another spelling. SHOW COLUMNS FROM students LIKE 'm%'; filters. information_schema.COLUMNS is the joinable catalog.

Trap — memorising both SHOW COLUMNS and DESC as ‘different concepts’. They answer the same question.

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

Exam tip

SHOW COLUMNS FROM students; = DESCRIBE students;

Show Columns — sample query

-- Show Columns
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;

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

Short notes

DefSHOW COLUMNS FROM t; lists columns.
RuleSame job as DESCRIBE.
TrapTreating them as two different topics.

-- Show Columns 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;

Show Columns

Show Columns — sample query

Short notes

Questions

Show Columns

Show Columns — sample query

Short notes

Questions