如何在Mysql中计算2 Count（*）的和

Question

我有两个表，我计算它们的行数。

SELECT COUNT(*) 
FROM docgrados_directores 
WHERE docgrados_directoresleido = '0' AND docgrados_directoresusu = '11' 

result 1

SELECT COUNT(*) 
FROM docgrados_lectores 
WHERE docgrados_lectoresleido = '0' AND docgrados_lectoresusu = '11'

result 1

我需要总数（结果是2）。如何用单个语句对结果求和？什么是正确的语法??

Answer 1

使用另一个SELECT添加查询返回的标量值：

SELECT (SELECT COUNT(*) 
        FROM docgrados_directores 
        WHERE docgrados_directoresleido = '0' AND docgrados_directoresusu = '11' ) 
       +    
      (SELECT COUNT(*) 
       FROM docgrados_lectores 
       WHERE docgrados_lectoresleido = '0' AND docgrados_lectoresusu = '11')

如果两个子查询的结果都是2，则上述语句应返回1。