Question

您好我正在尝试执行此简单语句但我想添加一个来自select的变量。这就是我所拥有的。

 userEmail varChar(50) := SELECT user_id FROM users WHERE email = 'email@email.com';
        SELECT * 
        FROM iphone_alerts
        WHERE user_id =  userEmail
        AND date_added = (SELECT MAX(date_added) FROM iphone_alerts WHERE user_id = userEmail

我是否需要使用Declare和Begins的内容？我是sql的新手，我很难找到答案。

Answer 1

你需要：

declare
    userEmail varchar2(200);
begin
    select user_id into userEmail
      from users
     where email = 'email@email.com';

    -- you will need a cursor to itare these results
    select * 
      from iphone_alerts
     where user_id =  userEmail
       and date_added = (select max(date_added) from iphone_alerts WHERE user_id);

end;

评论后编辑：

如果select只返回一行，则不需要游标，但需要into子句将每个检索到的值存储到变量中。类似的东西：

declare
    userEmail varchar2(200);
    v_field1 number; 
    v_field2 date;
    v_field3 varchar2(200);
begin
    select user_id into userEmail
      from users
     where email = 'email@email.com';

    -- you will need a cursor to itare these results
    select field1, field2, field3
      into v_field1, v_field2, v_field3
      from iphone_alerts
     where user_id =  userEmail
       and date_added = (select max(date_added) from iphone_alerts WHERE user_id);

end;

Answer 2

如果你想在SQL中这样做，你需要像

这样的东西

SELECT alerts.*
  FROM iphone_alerts alerts,
       users 
 WHERE alerts.user_id = users.user_id
   AND users.email = 'email@email.com'
   AND alerts.date_added = (SELECT MAX(date_added)
                              FROM iphone_alerts alerts2
                             WHERE alerts2.user_id = user.user_id)

这样的效率可能会让我们只打一次IPHONE_ALERTS表。

SELECT <<list of columns in IPHONE_ALERTS>>
  FROM (
    SELECT alerts.*,
           RANK() OVER (PARTITION BY alerts.user_id ORDER BY date_added DESC) rnk
      FROM iphone_alerts alerts,
           users 
     WHERE alerts.user_id = users.user_id
       AND users.email = 'email@email.com'
  )
 WHERE rnk = 1

Answer 3

我不确定你要做什么，但我认为你可能需要select into

declare 
    V_userID varChar(50) ;
begin
    /*This will store the value of the user_id field into the v_userID variable.*/
    SELECT user_id into v_userID FROM users WHERE email = 'email@email.com';
end;

http://download.oracle.com/docs/cd/B13789_01/appdev.101/b10807/13_elems045.htm

带有变量帮助的PLSQL select语句

3 个答案: