SQL查询避免 left join

背景

最近项目中有个查询接口非常慢 ，该SQL是主表left join了两张表，主表和另外两张表中都有可能作为查询条件的字段，当另外两张表的字段没有作为筛选条件时，查询效率非常慢，于是做了以下优化。

优化前：

select s.contract_no,
	s.plan_no,
	s.box_shape_num,
	s.customer_name,
	s.countries_code,
	s.countries_name,
	s.total_volume,
	s.total_gross_weight,
	s.factory_approval_state
from standard_scheme s
left join standard_scheme_material s3 on s3.standard_scheme_id = s.plan_no
LEFT JOIN act_order_special_cnt aos ON aos.special_cnt_cdoe = s.plan_no
<where>
	<if test="vo.planNo != null and vo.planNo != '' ">
		and s.plan_no like concat('%',#{vo.planNo},'%')
	</if>
	<if test="vo.materialCode != null and vo.materialCode != '' ">
		and s3.material_code = #{vo.materialCode}
	</if>
	<if test="vo.orderCode != null and vo.orderCode != '' ">
		AND aos.order_id = #{vo.orderCode}
	</if>
</where>
GROUP BY s.plan_no
ORDER BY s.create_time DESC

优化后：

select s.contract_no, 
	s.plan_no, 
	s.box_shape_num, 
	s.customer_name,
  	s.countries_code, 
  	s.countries_name, 
  	s.total_volume, s.total_gross_weight,
  	s.factory_approval_state
from standard_scheme s
<where>
	<if test="vo.planNo != null and vo.planNo != '' ">
		and s.plan_no like concat('%',#{vo.planNo},'%')
	</if>
	<if test="vo.materialCode != null and vo.materialCode != '' ">
		and s.plan_no in (
			SELECT standard_scheme_id 
			FROM standard_scheme_material 
			where material_code = #{vo.materialCode}
		)
	</if>
	<if test="vo.orderCode != null and vo.orderCode != '' ">
		and s.plan_no in (
			SELECT special_cnt_cdoe 
			FROM act_order_special_cnt 
			where order_id = #{vo.orderCode}
		)
	</if>
</where>
GROUP BY s.plan_no
ORDER BY s.create_time DESC

查询时间比对

优化前全量查询

优化后全量查询