Mysql - 获得没有以前状态的行

Question

我有一个表保持Sample状态。

id  sample_id    previous_status  current_status 
1  22216     NULL     1 
2  22216     1      3 
3  22221     NULL     1 
4  22221     1      3 

我想找到这在目前的状况没有条目1

编辑（从评论）该行： 我想这有PREVIOUS_STATUS = 1，现状样品ID = 3和NO行与PREVIOUS_STATUS = NULL，CURRENT_STATUS = 1

Answer 1

我想具有PREVIOUS_STATUS = 1，当前状态= 3和NO行与PREVIOUS_STATUS = NULL，CURRENT_STATUS = 1

样品ID

你可以使用相关子查询：

SELECT s1.sample_id 
FROM Sample s1 
WHERE previous_status = 1 
    AND current_status = 3 
    AND NOT EXISTS (SELECT 1 
        FROM Sample s2 
        WHERE s2.sample_id=s1.sample_id 
        AND s2.previous_status IS NULL 
        AND s2.current_status = 1); 

SqlFiddleDemo

---

使用GROUP BY：

SELECT sample_id 
FROM Sample 
GROUP BY sample_id 
HAVING SUM(previous_status = 1 AND current_status = 3) > 0 
    AND SUM(previous_status IS NULL AND current_status = 1) = 0; 

SqlFiddleDemo2

Answer 2

尝试，

Select * from Sample where previous_status =1 and current_status = 3 and previous_status IS NOT NULL and current_status <>1 

其中<>不等于

http://sqlfiddle.com/#!9/1c9f55/9 （采取童子的sqlfiddle）