MySQL 8.0

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CREATE TABLE wpmega_postmeta(
   meta_id    INTEGER  NOT NULL PRIMARY KEY 
  ,post_id    INTEGER  NOT NULL
  ,meta_key   VARCHAR(37) NOT NULL
  ,meta_value INTEGER  NOT NULL
);
INSERT INTO wpmega_postmeta(meta_id,post_id,meta_key,meta_value) VALUES (12,161,'unavailable_dates',2);
INSERT INTO wpmega_postmeta(meta_id,post_id,meta_key,meta_value) VALUES (16,161,'unavailable_dates_0_dates_from_date',20200610);
INSERT INTO wpmega_postmeta(meta_id,post_id,meta_key,meta_value) VALUES (18,161,'unavailable_dates_0_dates_to_date',20200630);
INSERT INTO wpmega_postmeta(meta_id,post_id,meta_key,meta_value) VALUES (30,161,'unavailable_dates_1_dates_from_date',20200701);
INSERT INTO wpmega_postmeta(meta_id,post_id,meta_key,meta_value) VALUES (32,161,'unavailable_dates_1_dates_to_date',20200709);
INSERT INTO wpmega_postmeta(meta_id,post_id,meta_key,meta_value) VALUES (62,260,'unavailable_dates',1);
INSERT INTO wpmega_postmeta(meta_id,post_id,meta_key,meta_value) VALUES (56,260,'unavailable_dates_0_dates_from_date',20200801);
INSERT INTO wpmega_postmeta(meta_id,post_id,meta_key,meta_value) VALUES (58,260,'unavailable_dates_0_dates_to_date',20200830);

post_id	from_date	to_date
161	20200610	20200630
161	20200701	20200709
260	20200801	20200830