Question

SQL一个表中有A、B、C三个属性，如何用count()将BC所有相同的组合的数据项的数量统计出来？

Answer 1

select count(*) from table
group by b,c

Answer 2

select count(b)
from T
where C=B
.........................

Answer 3

select count(1) from table_name where b=c

Answer 4

select count(*) from table_name where b=c