如何优化sql查询效率

select '合  计',sum(t.zgjl),sum(t.zbjl),sum(t.zqjl) ,sum(t.xljl),sum(t.skjl),sum(t.bgjl),sum(t.bqjl),sum(t.bgjl2),
sum(t.pxjl),sum(t.ccjl),sum(t.xjjl),sum(t.jdjl),sum(t.wyjl),sum(t.xxjl), 

(sum(t.zgjl)+sum(t.pxjl)+sum(t.ccjl)+sum(t.xjjl)+sum(t.jdjl)+sum(t.wyjl)+sum(t.xxjl)) 

  from (select code_mean as dwmc,

  (select count(*) from t_dtjl_jldd b, a01 a where a.leader_code=b.leader_code and a.a0199 <'5' and
b.szdwdm=code and to_char(b.rq,'yyyy-MM-dd')=to_char(sysdate,'yyyy-MM-dd') and b.zgzt in
('0101','0102','0103','0104','0205','0206','0105')) zgjl ,
  (select count(*) from t_dtjl_jldd b, a01 a where a.leader_code=b.leader_code and a.a0199 <'5' and b.zgzt='0102' and b.szdwdm=code and to_char(b.rq,'yyyy-MM-dd')=to_char(sysdate,'yyyy-MM-dd')) zbjl,
  (select count(*) from t_dtjl_jldd b, a01 a where a.leader_code=b.leader_code and a.a0199 <'5' and b.zgzt='0103' and b.szdwdm=code and to_char(b.rq,'yyyy-MM-dd')=to_char(sysdate,'yyyy-MM-dd')) zqjl,
  (select count(*) from t_dtjl_jldd b, a01 a where a.leader_code=b.leader_code and a.a0199 <'5' and b.zgzt='0205' and b.szdwdm=code and to_char(b.rq,'yyyy-MM-dd')=to_char(sysdate,'yyyy-MM-dd')) xljl,
&