java - pertanyaan pangkalan data berbilang jadual

Question

Oralce prasyarat, mybatis kini mempunyai berbilang jadual saya kini perlu mengira jumlah maklumat dalam setiap jadual, iaitu, count(*) Kaedah semasa saya adalah untuk menulis pelbagai kaedah, seperti dalam pemeta: long selectCountB; long selectCountC ; Dalam kes ini, saya mahu...

巴扎黑 · Answer

select "a" name, count(1)
from tableA
union
select "b" name, count(1)
from tableB
union
select "C" name, count(1)
from tableC

Gunakan kaedah penulisan berbilang lajur

with 
temp_a as (select count(*) num from talbeA),
temp_b as (select count(*) num from tableB),
temp_c as (select count(*) num from tableC)
select temp_a.num, temp_b.num, temp_c.num from dual;

PHPz · Answer

select A.countA,B.countB from (select count(*) as countA from t_countA) as A ,(select count(*) as countB from t_countB) as B

Macam ni?

过去多啦不再A梦 · Answer

Mysql

Oracle
Tambah daripada dual

selepas kenyataan di atas

某草草 · Answer

Mysql
select table_rows from information_schema.TABLES where table_schema in ('schema1','schema2','scheman') and table_name in ('tableName1','tableName2','tableNameN')
Saya percaya oralce juga mempunyai jadual sistem yang serupa