使用条件/if else/case 生成列以填充新列 mysql

Question

我有一个列-City，我想创建一个新列-Metro，我希望它检查 if city in('x','y','z') then Metro='Metro' else 'Non metro'

   ALTER TABLE sales ADD COLUMN Metro_city VARCHAR(45) GENERATED ALWAYS AS  (IF (CITY in('Mumbai ','Delhi' , 'Bangalore') then Metro_city='Metro') ('Non-Metro' end if)) STORED;

我还有另一组值要放在 case 中，但我猜如果我能做到这一点，那也会。我希望它存储到表中，而不是选择查询

Answer 1

您需要修复case 表达式，基本上：

ALTER TABLE sales ADD COLUMN Metro_city VARCHAR(45) GENERATED ALWAYS AS
      (case when CITY in ('Mumbai ', 'Delhi' , 'Bangalore')
            then 'Metro'
            else 'Non-Metro'
       end ) STORED;