欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  数据库

mysql语句入门详解

程序员文章站 2022-04-10 10:25:59
...

本文主要和大家分享mysql语句入门详解,专门和大家一步一步详解mysql语句,希望能帮助到大家。

Select,Left Join的用法,及模糊查询的实现:

LEFT JOIN 关键字会从左表 (table_name1) 那里返回所有的行,即使在右表 (table_name2) 中没有匹配的行。
(业务需求:从一张表查询出来的数据要关联到另一个表,并实现模糊查询)

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

(业务需求:当某个字段有传进来时就更新,没有传进来时忽略,这样可以根据你的需求来选择是否插入某个字段)

const contactRemarkSql = isUpdateRemark ? ',contactRemark=:contactRemark' : '';
const sql = `update cm_engineer_intentions
set intentionStatus=:intentionStatus ${contactRemarkSql}
where intentionID=:intentionID`;

Delete,In的用法:(IN 操作符允许我们在WHERE子句中规定多个值)

下面的SQL语句可以删除多条符合条件的数据
(业务需求: 进行删除操作时,创建数据的人若是操作数据的人,则删除,否则更新状态)
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

(业务需求: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)

(业务需求: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`;

(业务需求: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

相关推荐:

实现MySQL语句加锁的方法

用mysql语句创建数据表详细教程

对mysql语句的性能分析与优化

以上就是mysql语句入门详解的详细内容,更多请关注其它相关文章!