是否可以用一条SQL实现解决方法

是否可以用一条SQL实现

user表中有phone字段（是手机号）,现在需要统计移动、联通、电信的手机好个数

SQL code

  // ============1===========移动
   select count(*) from 
       (select substr(user.phone, 1, 3) as flag from user)t
   where flag in ('134', '135', '136', '137', '138', '139', '150', '151', '152', '157', '158', '159', '187', '188')
   

SQL code

   // ============2===========联通
   select count(*) from 
       (select substr(user.phone, 1, 3) as flag from user)t
   where flag in ('130', '131', '132', '155', '156', '185', '186')

SQL code

  // ============3===========电信
   select count(*) from 
       (select substr(user.phone, 1, 3) as flag from user)t
   where flag in ('180', '189', '133', '153')

怎么能一条SQL查出这三个结果？

select ‘移动’,count(*) from 

(select substr(user.phone, 1, 3) as flag from user)t1

where flag in (‘134’, ‘135’, ‘136’, ‘137’, ‘138’, ‘139’, ‘150’, ‘151’, ‘152’, ‘157’, ‘158’, ‘159’, ‘187’, ‘188’)

union all

select ‘联通’,count(*) from 

(select substr(user.phone, 1, 3) as flag from user)t2

where flag in (‘130’, ‘131’, ‘132’, ‘155’, ‘156’, ‘185’, ‘186’)SQL code

select ‘电信’,count(*) from 

(select substr(user.phone, 1, 3) as flag from user)t3

where flag in (‘180’, ‘189’, ‘133’, ‘153’)

SQL code

select
sum(
 case 
  when flag in ('134', '135', '136', '137', '138', '139', '150', '151', '152', '157', '158', '159', '187', '188') 
    then 1 
  else 0
 end) as 移动,
sum(
 case 
  when flag in('180', '189', '133', '153')
    then 1 
  else 0 
 end) as 联通,
sum(
 case 
  when flag in('130', '131', '132', '155', '156', '185', '186')
    then 1 
  else 0 
 end) as 电信
from 
(select substr(user.phone, 1, 3) as flag from user)t