Postgres 15

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE test(
  teacher text
, grade text
, district text
);

INSERT INTO test VALUES
  ('Mr. Smith'  ,'3rd','West')
, ('Mrs. John'  ,'4th','South')
, ('Mr. Cameron','2nd','North')
, ('Mr. Cameron','2nd','North')
, ('Kirk Horn'  ,'1st','West')
;

CREATE TABLE



INSERT 0 5


SELECT t.*  -- or your list of columns
FROM   test t
     , generate_series(1, CASE WHEN t.teacher = 'Mr. Cameron' THEN 2 ELSE 1 END);


teacher
grade
district


Mr. Smith
3rd
West

Mrs. John
4th
South

Mr. Cameron
2nd
North

Mr. Cameron
2nd
North

Mr. Cameron
2nd
North

Mr. Cameron
2nd
North

Kirk Horn
1st
West



SELECT 7


SELECT teacher, grade, district
FROM   test t
JOIN   LATERAL (VALUES (1),(2)) x(v) ON v = 1 OR teacher = 'Mr. Cameron';


teacher
grade
district


Mr. Smith
3rd
West

Mrs. John
4th
South

Mr. Cameron
2nd
North

Mr. Cameron
2nd
North

Mr. Cameron
2nd
North

Mr. Cameron
2nd
North

Kirk Horn
1st
West



SELECT 7


-- Ergest
SELECT teacher, grade, district
FROM   test
UNION ALL
SELECT teacher, grade, district
FROM   test
WHERE  teacher = 'Mr. Cameron';


teacher
grade
district


Mr. Smith
3rd
West

Mrs. John
4th
South

Mr. Cameron
2nd
North

Mr. Cameron
2nd
North

Kirk Horn
1st
West

Mr. Cameron
2nd
North

Mr. Cameron
2nd
North



SELECT 7

teacher	grade	district
Mr. Smith	3rd	West
Mrs. John	4th	South
Mr. Cameron	2nd	North
Mr. Cameron	2nd	North
Mr. Cameron	2nd	North
Mr. Cameron	2nd	North
Kirk Horn	1st	West