mysql - 来自 MySQL 中多个表的 COUNT(*)

Question

如何从 MySQL 的多个表中选择 COUNT(*)？

如:

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

编辑:

目标是返回这个:

+-------------+-------------+-------------+
| table1Count | table2Count | table3Count |
+-------------+-------------+-------------+
| 14          | 27          | 0           |
+-------------+-------------+-------------+

Answer 1

您可以通过使用子查询来做到这一点，每个 tableCount 一个子查询:

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