本文主要和人人分享mysql语句入门详解，特地和人人一步一步详解mysql语句，希望能协助到人人。
Select,Left Join的用法,及隐约查询的完成：
LEFT JOIN 关键字会从左表 (table_name1) 那边返回一切的行，纵然在右表 (table_name2) 中没有婚配的行。
（营业需求：从一张表查询出来的数据要关联到另一个表，并完成隐约查询）
const sql = `select cei.intentionID,cei.engineerName,cei.nickname,cei.headImgUrl,
ifnull(cmw.headImgUrl,'') inviteImgUrl,ifnull(cmw.nickname,'') inviteNickName
from cm_engineer_intentions cei
left join cm_member_wechats cmw on cmw.referralCode=cei.inviteCode
where (:isGrant=-1 or isGrant=:isGrant)
and (:intentionStatus=-1 or intentionStatus=:intentionStatus)
and (:searchKey='' or concat(engineerMobile,engineerName) like concat('%',:searchKey,'%'))
order by intentionStatus asc,createTime desc`;
Update Set的用法
(营业需求：当某个字段有传进来时就更新，没有传进来时疏忽,如许能够依据你的需求来挑选是不是插进去某个字段)
const contactRemarkSql = isUpdateRemark ? ',contactRemark=:contactRemark' : '';
const sql = `update cm_engineer_intentions
set intentionStatus=:intentionStatus ${contactRemarkSql}
where intentionID=:intentionID`;
Delete,In的用法：(IN 操纵符许可我们在WHERE子句中划定多个值)
下面的SQL语句能够删除多条相符前提的数据
(营业需求: 举行删除操纵时，建立数据的人如果操纵数据的人，则删除，不然更新状况)
const deleteSql = delete from cm_fast_order_goods where orderGoodsID in (${deleteData.deleteIDs}) and createUser=:userName;
const updateSql = update cm_fast_order_goods set status=0 where orderGoodsID in (${deleteData.deleteIDs}) and createUser!=:userName;
Insert的用法
(营业需求：新增一条新的数据)
const sqlOrderEngineer = `insert into cm_order_engineers
(orderEngineerID,orderGoodsID,orderID,engineerID,engineerName,createUser,createTime)
values
(:orderEngineerID,:orderGoodsID,:orderID,:engineerID,:engineerName,:createUser,:createTime)
(营业需求：每新增一条数据，某一字段在原有的数据的最大值基础上+1)
const sql = `insert into cm_engineers
(engineerCode,loginName,password,engineerName,sex,birthDate,status,createUser,createTime)
select
ifnull(max(engineerCode),0)+1,:loginName,:password,:engineerName,:sex,:birthDate,
:status,:createUser,now()
from cm_engineers`;
(营业需求：从其他表中新增数据到当前表)
insert into cm_fast_order_goods (orderGoodsID,orderID,goodsID,goodsCode,goodsPicUrl,createUser,createTime)
select :orderGoodsID,:orderID,:goodsID,goodsCode,iconUrl,:createUser,now()
from cm_service_goods
where goodsID=:goodsID and status=1
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