MySQL 使用 SET 列名中的变量更新大表

Question

我必须使用 SET 列名作为从另一个表中选择的变量来更新表。 这是我的 MySQL :

UPDATE famcharts_old.db1w_matrix
JOIN famcharts_old.tbl_dirtosv
    ON famcharts_old.tbl_dirtosv.PlaceOT = famcharts_old.db1w_matrix.SERVICE_ID
    and famcharts_old.tbl_dirtosv.Dir_ID IN (a LIST-of-values)
JOIN famcharts_old.tbl__dir__base
    ON all_directives.DirID = famcharts_old.tbl_dirtosv.Dir_ID
SET famcharts_old.db1w_matrix.**@variable** = famcharts_old.tbl_dirtosv.NiceNeed;

@variable 来自选择，其中变量等于值列表中的 Id。

我尝试了几次 JOINS，但无法将 @variable 放入列的名称中。

Answer 1

尝试将此更新命令与准备好的语句一起使用

    set @variable = 'column_name';

    set @cmdSql = "UPDATE famcharts_old.db1w_matrix 
    JOIN famcharts_old.tbl_dirtosv ON famcharts_old.tbl_dirtosv.PlaceOT = 
    famcharts_old.db1w_matrix.SERVICE_ID
    and famcharts_old.tbl_dirtosv.Dir_ID IN (a LIST-of-values)
    JOIN famcharts_old.tbl__dir__base
    ON all_directives.DirID = famcharts_old.tbl_dirtosv.Dir_ID
    SET famcharts_old.db1w_matrix.";
    
    set @cmdSql=Concat(@cmdSql,@variable);
    
    set @cmdSql=Concat(@cmdSql," = famcharts_old.tbl_dirtosv.NiceNeed; ");
    
    
     Prepare execSQL from @cmdSql;

     Execute execSQL; 

     DEALLOCATE PREPARE execSQL;

更多说明查看：https://dev.mysql.com/doc/refman/8.4/en/sql-prepared-statements.html