Question

如何将标量[单行，单值]查询的结果传递给合并？我试图选择优先级（到目前为止表中最大的优先级）+ 1. [0如果它是第一行。]

create trigger priority_SuperRuleSamples before insert on SuperRuleSamples 
FOR EACH ROW 
  SET NEW.Priority=coalesce(NEW.Priority, 
   coalesce(
   select Priority from SuperRuleSamples order by Priority desc limit 1, 
   -1
   )+1
  )

Answer 1

您的查询中似乎存在括号问题。你能试试吗？


create trigger priority_SuperRuleSamples before insert on SuperRuleSamples 
FOR EACH ROW 
  SET NEW.Priority=coalesce(NEW.Priority, 
   coalesce(
    (select Priority from SuperRuleSamples order by Priority desc limit 1), 
   -1
   )+1
  )

将标量查询结果传递给coalesce

1 个答案: