COUNT（*）从MySQL中的多个表 [英] COUNT(*) from multiple tables in MySQL

问题描述

如何从MySQL的多个表格中选择COUNT（*）？

如：

  SELECT COUNT（*）AS table1Count FROM table1 WHERE someCondition 
 JOIN ?? 
 SELECT COUNT（*）AS table2Count FROM table2 WHERE someCondition 
 CROSS JOIN？子查询？ 
 SELECT COUNT（*）AS table3Count FROM table3 WHERE someCondition 
  

/ strong>

目标是返回：

  ------------- + ------------- + ------------- + 
 | table1Count | table2Count | table3Count | 
 + ------------- + ------------- + ------------- + 
 | 14 | 27 | 0 | 
 + ------------- + ------------- + ------------- + $ b $你可以使用子查询，每个tableCount一个子查询来完成它：b 
 $ 
 
 
 
  SELECT 
（SELECT COUNT（*）FROM table1 WHERE someCondition）as table1Count，
 （*）FROM table2 WHERE someCondition）as table2Count，
（SELECT COUNT（*）FROM table3 WHERE someCondition）as table3Count 
  
 
How do I go about selecting COUNT(*)s from multiple tables in MySQL?

Such as:
SELECT COUNT(*) AS table1Count FROM table1 WHERE someCondition
JOIN?? 
SELECT COUNT(*) AS table2Count FROM table2 WHERE someCondition
CROSS JOIN? subqueries?
SELECT COUNT(*) AS table3Count FROM table3 WHERE someCondition
Edit:

The goal is to return this:
+-------------+-------------+-------------+
| table1Count | table2Count | table3Count |
+-------------+-------------+-------------+
| 14          | 27          | 0           |
+-------------+-------------+-------------+

解决方案
You can do it by using subqueries, one subquery for each tableCount :
SELECT
  (SELECT COUNT(*) FROM table1 WHERE someCondition) as table1Count, 
  (SELECT COUNT(*) FROM table2 WHERE someCondition) as table2Count,
  (SELECT COUNT(*) FROM table3 WHERE someCondition) as table3Count


                        
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