计算第二个表中外键数量并与第一个表中的行一起显示的有效方法 - PHP - MySQL [英] Efficient way to calculate number of foreign keys in second table and display it with rows from first table - PHP - MySQL

问题描述

我有两个表 tablea 和 tableb 如下所示；

I have two tables tablea and tableb like below;

表格

+--------+-------+-------+-------+------+
|   fa   |   fb  |  fc   |  fd   |  fe  |
+--------+-------+-------+-------+------+
|  col1  |  f11  |  f12  |  f13  |  x1  |
+--------+-------+-------+-------+------+
|  col2  |  f21  |  f22  |  f23  |  x2  |
+--------+-------+-------+-------+------+
|  col3  |  f31  |  f32  |  f33  |  x3  |
+--------+-------+-------+-------+------+
|  col4  |  f41  |  f42  |  f43  |  x4  |
+--------+-------+-------+-------+------+

tableb

+--------+-------+-------+-------+------+
|  tbba  |  tbbb |  tbbc |  tbbd | tbbe |
+--------+-------+-------+-------+------+
|  cola  |  fa1  |  fa2  |  fa3  |  x1  |
+--------+-------+-------+-------+------+
|  colb  |  fb1  |  fb2  |  fb3  |  x1  |
+--------+-------+-------+-------+------+
|  colc  |  fc1  |  fc2  |  fc3  |  x1  |
+--------+-------+-------+-------+------+
|  cold  |  fd1  |  fd2  |  fd3  |  x2  |
+--------+-------+-------+-------+------+
|  cole  |  fe1  |  fe2  |  fe3  |  x2  |
+--------+-------+-------+-------+------+
|  colf  |  ff1  |  ff2  |  ff3  |  x3  |
+--------+-------+-------+-------+------+
|  colg  |  fg1  |  fg2  |  fg3  |  x3  |
+--------+-------+-------+-------+------+
|  colh  |  fh1  |  fh2  |  fh3  |  x3  |
+--------+-------+-------+-------+------+
|  coli  |  fi1  |  fi2  |  fi3  |  x3  |
+--------+-------+-------+-------+------+
|  colj  |  fj1  |  fj2  |  fj3  |  x4  |
+--------+-------+-------+-------+------+

我想生成一个表格；

+--------+-------+-----+
|  col1  |  f11  |  3  |
+--------+-------+-----+
|  col2  |  f21  |  2  |
+--------+-------+-----+
|  col3  |  f31  |  4  |
+--------+-------+-----+
|  col4  |  f41  |  1  |
+--------+-------+-----+

数字表示tablea的fe字段中的条目出现在tableb中的次数.目前，我正在从 tablea 中获取所有行，并且在每个循环中，我使用另一个查询来获取 tableb 中的行数，使用 tablea 的 fe 字段.因此，我有 1 个主查询和 4 个子查询.有没有什么有效的方法，比如加入什么的?

The number denotes the times where entry in fe field of tablea appears in tableb. Currently, I am fetching all rows from the tablea, and in each loop, I use another query to get number of rows in tableb, using tablea's fe field. Thus, I have 1 main query, and 4 sub queries. Is there any efficient way like join or something?

谢谢

推荐答案

试试这个:

SELECT a.fa , a.fb , COUNT( b.tbbe) 
FROM  tablea a
LEFT JOIN tableb b ON a.fe = b.tbbe
GROUP BY a.fa 

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