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How to write SQL statements: the usage of Update, Case, and Select together

2022-08-04 14:14:00 【51CTO】

修改数据,The corresponding data needs to be modified after verification,And the validated fields are no longer modified in the table,You need to query multiple tables,Took some time to come up with the following solution,感觉还是挺有用的,Also quite enjoyable,Rarely encountered this before,So record it again：

(This business logic is not detailed,If you are looking at these,只需要看SQLwritten grammar,I believe you can understand,也希望对您有所帮助)

       
       -----------------------------------------
       
       --Update 与 Select usage together
       
       --Update Modify data through multiple tables
       
       -----------------------------------------
       
       --参考写法1：
       
       update B1 
       
       set strNum 
       
       = strNum 
       
       - B2
       
       .intNum
       
       where strId 
       
       in 
       
       (
       
       select intId 
       
       from B2 
       
       where B2
       
       .intId 
       
       = B1
       
       .strId
       
       )
       
       --参考写法2：
       
       update B1 
       
       set strNum 
       
       = strNum 
       
       - B2
       
       .intNum
       
       from B1 inner 
       
       join B2
       
       on B2
       
       .intId 
       
       = B1
       
       .strId
       
       select 
       
       * 
       
       from pro_res_assign
       
       ,pro_gantt_task
       
       where pro_res_assign
       
       .task_id 
       
       = pro_gantt_task
       
       .task_id
       
       and pro_res_assign
       
       .resource_id 
       
       = 
       
       'jxstar4918'
       
       update pro_gantt_task 
       
       set pro_gantt_task
       
       .responsible_id 
       
       = pro_res_assign
       
       .user_id 
       
       ,
       
  pro_gantt_task
       
       .responsible 
       
       =  pro_res_assign
       
       .res_name
       
       from pro_res_assign
       
       ,pro_gantt_task
       
       where pro_res_assign
       
       .task_id 
       
       = pro_gantt_task
       
       .task_id
       
       and pro_res_assign
       
       .resource_id 
       
       = 
       
       'jxstar4918'
       
       ------------------------------
       
       --最终完成的SQL
       
       ------------------------------
       
       update pro_gantt_task 
       
       set pro_gantt_task
       
       .responsible_id 
       
       = 
       
       (
       
    case when pro_res_assign
       
       .responsible_type 
       
       = 
       
       '1' then pro_res_assign
       
       .user_id else 
       
       null end  
       
       )
       
       ,
       
pro_gantt_task
       
       .responsible 
       
       =  
       
       (
       
  case when pro_res_assign
       
       .responsible_type 
       
       = 
       
       '1' then pro_res_assign
       
       .res_name else 
       
       null end  
       
       )
       
       from pro_res_assign
       
       ,pro_gantt_task
       
       where pro_res_assign
       
       .task_id 
       
       = pro_gantt_task
       
       .task_id
       
       and pro_res_assign
       
       .resource_id 
       
       = 
       
       'jxstar4918'
       
       --测试查询
       
       select res_type
       
       ,user_id
       
       ,res_name
       
       ,task_id 
       
       from pro_res_assign 
       
       where resource_id 
       
       = 
       
       'jxstar4918'
       
       select responsible_id
       
       ,responsible 
       
       from pro_gantt_task
       
以下是WBSSchedule reverse write backups：
       
       --select user_id,res_name,task_id from pro_res_assign where resource_id = ?
       
       --update pro_gantt_task set responsible_id = ? ,responsible = ? where task_id = ?
      
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这里只对SQL Server2008 测试通过,不知道Oracle/Mysql Other databases have not been tested;

原网站

版权声明
本文为[51CTO]所创，转载请带上原文链接，感谢
https://yzsam.com/2022/216/202208041405332304.html

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How to write SQL statements: the usage of Update, Case, and Select together

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