SQL HowTo: замена в строке по набору

CREATE OR REPLACE FUNCTION replace_multiple(input_string TEXT, replacements TEXT[])
  RETURNS TEXT AS
$$
DECLARE
  i INT;
BEGIN
  IF cardinality(replacements) % 2 <> 0 THEN
    RAISE EXCEPTION 'Number of replacements must be even';
  END IF;
  
  FOR i IN 1..cardinality(replacements)/2 LOOP
    input_string := replace(input_string, replacements[(i-1)*2+1], replacements[i*2]);
  END LOOP;
  
  RETURN input_string;
END;
$$
LANGUAGE plpgsql;

Можно значительно проще и экономнее на regexp

Пример на MySQL (на PG думаю будет аналогично):

WITH d AS (
    SELECT 'abcdaaabbbcccdcba' s
    , 'a,x;bb,y;ccc,z;' repls
    , 'xbcdxxxybzdcbx' test_res
)
, d2 AS (
    SELECT *, CONCAT(s, '\n', repls) s_ex
    FROM d
)
, d3 AS (
    SELECT *
    , SUBSTRING_INDEX(REGEXP_REPLACE(s_ex, '(?<search>[^\n]+)(?=.*?(\n|\n.*?;)\\\k<search>,(?<repl>[^;]+);)', '${repl}', 1, 0, 'm'), '\n', 1) res
    FROM d2 d
)
SELECT s, res
, res = test_res is_correct
, VERSION() ver
FROM d3

+-----------------+--------------+----------+-----+
|s                |res           |is_correct|ver  |
+-----------------+--------------+----------+-----+
|abcdaaabbbcccdcba|xbcdxxxybzdcbx|1         |8.3.0|
+-----------------+--------------+----------+-----+

Нашёл подобное приемлемое решение на MySQL как закапиталайзить предложение

WITH d AS (
    SELECT 'Lorem Ipsum is simply dummy text of the printing and typesetting industry.' s
)
, d2 AS (
    SELECT *
    , CONCAT(LOWER(s), UPPER(s)) s_l_u
    , CONCAT('(?<=[[:space:]]|^)[a-z](?=.{', (CHAR_LENGTH(s) - 1), '}([A-Z]))') reg_exp
    , CHAR_LENGTH(s) len
    FROM d
)
SELECT version() ver, s, SUBSTR(REGEXP_REPLACE(s_l_u, reg_exp, '$1'), 1, len) cap
FROM d2

+------+--------------------------------------------------------------------------+--------------------------------------------------------------------------+
|ver   |s                                                                         |cap                                                                       |
+------+--------------------------------------------------------------------------+--------------------------------------------------------------------------+
|8.0.35|Lorem Ipsum is simply dummy text of the printing and typesetting industry.|Lorem Ipsum Is Simply Dummy Text Of The Printing And Typesetting Industry.|
+------+--------------------------------------------------------------------------+--------------------------------------------------------------------------+