从 MySQL/oracle 中的多个表中计数

Question

有 4 个表：A,B,C,D
有一个 id:4(input)
查询应该打印 id 在表中出现的次数

前：

in table A id:4 occurs 5 times
in table B id:4 occurs 7 times
in table C id:4 occurs 3 times
in table D id:4 occurs 1 times

输出：

Table name       No of occurence

A                   5
B                   7
C                   3
D                   1

Answer 1

你可以试试这样的：

select 'A', count(*) from a where id = 4
union all
select 'B', count(*) from b where id = 4
union all
select 'C', count(*) from c where id = 4
union all
select 'D', count(*) from d where id = 4

Answer 2

select id as Name,count(id) as occurence from tableA where id = 4 group by id
union all
select id as Name,count(id) as occurence from tableB where id = 4 group by id
union all
select id as Name,count(id) as occurence from tableC where id = 4 group by id
union all
select id as Name,count(id) as occurence from tableD where id = 4 group by id

Answer 3

执行union all

select 'A' as Name, count(*) as occurence from tablea where id = ?
union all
select 'B' as Name, count(*) as occurence from tableb where id = ?
union all
select 'C' as Name, count(*) as occurence from tablec where id = ?
union all
select 'D' as Name, count(*) as occurence from tabled where id = ?