專案中經常用到sql語句進行資料增刪查改操作,下面總結了一下:
比如 查詢指定客戶最近訂單
根據id查詢按日期降序排序取第一條。(降序排序取第一條)
select * from t_customer_order where cusid=# order by orderdate desc limit 0,1;
查詢存在乙個表而不在另乙個表中的資料記錄
select a.id from a where a.id not in (select id from b)
查詢某個欄位為null的記錄
select lastname,firstname,address from persons where address is null
select
excute.i_id as id,
excute.i_plan_drill_id as drillid,
excute.i_status as status,
info.c_name as planname,
excute.c_alarm_source_name as alarmsourcename,
excute.c_alarm_event_name as alarmeventname,
excute.c_alarm_area as alarmarea,
excute.c_creator as creator,
excute.d_create_time as createtime
from
plan_excute excute,
plan_info info
where
excute.i_plan_id = info.i_id
andexcute.i_plan_drill_id is null
order by
excute.d_create_time desc
查詢客戶訂單總金額(牽涉到多表關聯查詢)
這裡牽涉到三個表,t_customer (客戶表),t_customer_order(客戶訂單表),t_order_details(客戶訂單詳情表),需用到左連線查詢和分組查詢
select t1.name,sum(t3.sum) as gx from t_customer t1 left join t_customer_order t2 on t1.id = t2.cusid left join t_order_details t3 on t2.id= t3.orderid group by t1.id
1、先左連線查詢出所有關聯記錄
2、再根據字段分組查詢所有記錄
3、最後查詢只關心的字段記錄
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