获取所有行具有相同列值的mysql数据

Question

我想获得所有具有相同零件价值的行，例如

1. lesson 1 part=1
2. lesson 1.1 part=1
3. lesson 2 part=2

我想上课1和1.1，因为它们的部分相等

wl - What lesson from math
lessons - first table
ls - second table
lid - lesson id from lessons table
Just to get non seen lessons.

"SELECT * FROM lessons 
WHERE wl='$math' 
AND id IN(SELECT lid FROM ls WHERE fid='$user' AND seen='0') 
GROUP BY part LIMIT 2";

Answer 1

因为这只是为了查找记录，所以足以获取每个零件的ID列表，您可以使用GROUP_CONCAT ：

SELECT part, GROUP_CONCAT(id) as ids
FROM lessons 
WHERE wl='$math' 
AND id IN(SELECT lid FROM ls WHERE fid='$user' AND seen='0') 
GROUP BY part
HAVING COUNT(*) > 1;

如果要每个零件和ID行，那将更加困难。 此类问题通常可以通过解析函数解决，但MySQL尚未提供这些功能。 这使得有必要写两次查询的一部分。

这是为用户提供看不见的课程的方法：

SELECT *
FROM lessons 
WHERE wl='$math' 
AND id IN(SELECT lid FROM ls WHERE fid='$user' AND seen='0');

这就是您如何获得在结果中多次出现的零件的方法：

SELECT part 
FROM lessons 
WHERE wl='$math' 
AND id IN(SELECT lid FROM ls WHERE fid='$user' AND seen='0') 
GROUP BY part
HAVING COUNT(*) > 1;

两者结合：

SELECT *
FROM lessons 
WHERE wl='$math' 
AND id IN(SELECT lid FROM ls WHERE fid='$user' AND seen='0')
AND part IN
(
  SELECT part 
  FROM lessons 
  WHERE wl='$math' 
  AND id IN(SELECT lid FROM ls WHERE fid='$user' AND seen='0') 
  GROUP BY part
  HAVING COUNT(*) > 1
);

Answer 2

对于您的条件“我需要2个相同的字符， 因为它们只能具有2个相同的字符” -使用以下查询：

SELECT 
    id, part
FROM 
    lessons 
WHERE 
    id REGEXP
    (SELECT 
        group_concat(id separator '|')
    FROM 
        lessons 
    WHERE 
        wl='$math' 
        AND id IN (SELECT lid FROM ls WHERE fid='$user' AND seen='0') 
    GROUP BY part
    HAVING count(part) = 2)