本文主要和大家分享mysql語句入門詳解，專門和大家一步一步詳解mysql語句，希望能幫助到大家。

Select,Left Join的用法,及模糊查詢的實現：

LEFT JOIN 關鍵字會從左表 (table_name1) 那里返回所有的行，即使在右表 (table_name2) 中沒有匹配的行。
（業務需求：從一張表查詢出來的數據要關聯到另一個表，并實現模糊查詢）

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

(業務需求：當某個字段有傳進來時就更新，沒有傳進來時忽略,這樣可以根據你的需求來選擇是否插入某個字段)

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

Delete,In的用法：(IN 操作符允許我們在WHERE子句中規定多個值)

下面的SQL語句可以刪除多條符合條件的數據
(業務需求: 進行刪除操作時，創建數據的人若是操作數據的人，則刪除，否則更新狀態)
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

(業務需求：新增一條新的數據)

const sqlOrderEngineer = `insert into cm_order_engineers
(orderEngineerID,orderGoodsID,orderID,engineerID,engineerName,createUser,createTime)
values
(:orderEngineerID,:orderGoodsID,:orderID,:engineerID,:engineerName,:createUser,:createTime)

(業務需求：每新增一條數據，某一字段在原有的數據的最大值基礎上+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`;

(業務需求：從其他表中新增數據到當前表)

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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