Postgres if语句在函数内插入值

Question

是否可以使此功能正常工作？我在 Postgres 函数的 Insert Into 查询中有 If 语句。

你有什么方法？

    CREATE FUNCTION proc_api_consumer_audit_insert()
    RETURNS TRIGGER AS $api_consumer$
    BEGIN
        INSERT INTO api_consumer_audit(api_consumer_id, change_type, changed_by, changed_date, business_id_old, business_id_new, name_old, name_new, api_callback_url_old, api_callback_url_new, application_base_url_old, application_base_url_new, authorization_callback_url_old, authorization_callback_url_new, status_old, status_new) 
        VALUES(NEW.id, 'INSERT', (IF NEW.created_by=null THEN CURRENT_USER ELSE NEW.created_by END IF;), CURRENT_TIMESTAMP, null, NEW.business_id, null, NEW.name, null, NEW.api_callback_url, null, NEW.application_base_url, null, NEW.authorization_callback_url, null, NEW.status);
        RETURN NEW;
    END;
    $api_consumer$ LANGUAGE plpgsql;

Answer 1

SQL 中没有IF。一般来说，人们会使用 CASE 表达式，但在你的情况下，coalesce() 要短得多：

INSERT INTO api_consumer_audit(...) 
VALUES (NEW.id, 
        'INSERT', 
        coalesce(new.created_by, current_user),
        ...);

与 CASE 表达式相同的是：

INSERT INTO api_consumer_audit(...) 
VALUES (NEW.id, 
        'INSERT', 
        case 
           when new.created_by IS NOT NULL then new.created_by
           else current_user
        end,
        ...);