一张表要想left join 两张表如何写sql语句
select
count(*)
from
customer_plan_punch
left join
customer_plan
on
customer_plan.id = customer_plan_punch.customer_plan_id
left join
health_punch_item
on
health_punch_item.id = customer_plan.plan_template_id
where
customer_plan.customer_id = #{customerId}
and
customer_plan.plan_class='HEALTH_PUNCH'
and
customer_plan.`status`=1
and
customer_plan_punch.punch_date >= #{startTime}
and
#{endTime} >= customer_plan_punch.punch_date
<if test="type == 0">
and
health_punch_item.label = "运动"
</if>
<if test="type == 1">
and
health_punch_item.label = "饮食"
</if>
<if test="type == 2">
and
health_punch_item.label = "睡眠"
</if>
<if test="type == 3">
and
health_punch_item.label = "其他"
</if>
写成sql就是
select
count(*)
from
customer_plan_punch
left join
customer_plan
on
customer_plan.id = customer_plan_punch.customer_plan_id
left join
health_punch_item
on
health_punch_item.id = customer_plan.plan_template_id
也就是说一张表用left join去惯量两张表，只需要left join。。。on两次就ok了
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