First run flush, repair, and optimize
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UPDATE tax SET STD = 9, DATE = '1990-01-01', percent = 14 WHERE STD = 1;
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INSERT INTO tax (NAME, percent, STD, DATE) VALUES ('VAT', 15, 1, '2018-04-01');

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DELETE FROM menu_tax WHERE id > 0;
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Now do flush, repaire and optimise and then
____________________________Then_____________

INSERT INTO menu_tax (menu_id,tax_id,DATE)
SELECT id,2,CURRENT_DATE FROM menu;

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NOTES: First check that the tax table has only 1 table in as id 1. If like that, then above.

If not like that, delete other lines, run flush, repair and optimize. Id must be i