MySQL跨多个表计数并获得单个值

Question

想象一下: t1 = 1 t2 = 3 t3 = 5

我需要在每个表上运行单独的选择，并以单个数量报告计数，即:

 select * 
   from (select count(*) from t1)
          + (select count(*) from t2)
          + (select count(*) from t3);

我的最终结果应该是 = 9

Answer 1

你很接近；你可以这样写:

 select (select count(*) from t1)
        + (select count(*) from t2)
        + (select count(*) from t3)
 ;