如何使数据库列成为另一列的 function

Question

I'm trying to make a database column which would be the percent of the value in another column

<?php
$sql = "ALTER TABLE inventorylist
        ADD COLUMN percent DOUBLE 
        GENERATED ALWAYS AS (turnover/SUM(turnover)*100);"; 
?>

Answer 1

As already commented generated columns can only refer to the columns of the same row. But you could try a view including the calculation. Something along the lines of:

CREATE VIEW inventorylist_with_percent
AS
SELECT il1.*,
       il1.turnover / (SELECT sum(il2.turnover)
                              FROM inventorylist il2) * 100 percent
       FROM inventorylist il1;

Answer 2

I think it will safe to say let your code logic handle that task instead of pushing it to the database. Write a code that does the computation while inserting or while querying from the database.