mysql四个统计数量语句 怎么合并在一个select里

可以使用UNION ALL将四个统计数量语句合并在一个SELECT语句中，如下：

SELECT COUNT(*) as count1, NULL as count2, NULL as count3, NULL as count4 FROM table1
UNION ALL
SELECT NULL as count1, COUNT(*) as count2, NULL as count3, NULL as count4 FROM table2
UNION ALL
SELECT NULL as count1, NULL as count2, COUNT(*) as count3, NULL as count4 FROM table3
UNION ALL
SELECT NULL as count1, NULL as count2, NULL as count3, COUNT(*) as count4 FROM table4

上面的语句中，每个SELECT语句都返回一个统计数量，使用UNION ALL将这四个语句合并在一起。在每个SELECT语句中，使用NULL填充其他列，以确保每个SELECT语句返回相同的列数和列顺序。最终的结果将是一个包含四个统计数量的结果集。