Postgres 9.6

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CREATE OR REPLACE FUNCTION pctDisplay (pct numeric, ch text = '|', length int = 20, includeLabel boolean = TRUE) RETURNS text AS $$
DECLARE x TEXT;
BEGIN
	IF length < 1 OR length > 100 THEN
		length = 20;
	END IF;

	IF pct < 0 THEN
		pct = 0;
	ELSEIF pct > 100 THEN
		pct = 100;
	END IF;

	SELECT ch ||
		rpad(repeat(ch, ((pct / 100) * length)::int - 2), length - 2) ||
		ch ||
		CASE WHEN includeLabel THEN ' ' || round(pct, 1)::text || '%' ELSE '' END
		INTO x;

	RETURN x;
END
$$ LANGUAGE PLPGSQL;

select pctDisplay(50);

pctdisplay

|||||||||          | 50.0%

select pctDisplay(1);

pctdisplay

|                  | 1.0%

select pctDisplay(10);

pctdisplay

|                  | 10.0%

select pctDisplay(20);

pctdisplay

|||                | 20.0%

select pctDisplay(25);

pctdisplay

||||               | 25.0%

select pctDisplay(50);

pctdisplay

|||||||||          | 50.0%

select pctDisplay(75);

pctdisplay

||||||||||||||     | 75.0%

select pctDisplay(90);

pctdisplay

|||||||||||||||||  | 90.0%

select pctDisplay(95);

pctdisplay

|||||||||||||||||| | 95.0%

select pctDisplay(100);

pctdisplay

|||||||||||||||||||| 100.0%

select pctDisplay(-100);

pctdisplay

|                  | 0.0%

select pctDisplay(1000);

pctdisplay

|||||||||||||||||||| 100.0%

select pctDisplay(50, 'X', 100, false);

pctdisplay

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX                                                  X

select pctDisplay(77, '❚', 100, true);

pctdisplay

❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚❚                       ❚ 77.0%

select pctDisplay(77, '❚', 10, true);

pctdisplay

❚❚❚❚❚❚❚  ❚ 77.0%

select pctDisplay(77, '❚', 5, true);

pctdisplay

❚❚❚ ❚ 77.0%

select pctDisplay(77, '❚', 3, true);

pctdisplay

❚ ❚ 77.0%

select pctDisplay(77, '❚', 1, true);

pctdisplay

❚❚ 77.0%