这篇文章主要为大家展示了“mysql中入门语句的示例分析”，内容简而易懂，条理清晰，希望能够帮助大家解决疑惑，下面让小编带领大家一起研究并学习一下“mysql中入门语句的示例分析”这篇文章吧。
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
以上是“mysql中入门语句的示例分析”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注亿速云行业资讯频道！
