MySQL通过视图（或临时表）实现动态SQL（游标）

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写MySQL存储过程实现动态执行SQL

Dynamic cursor in stored procedure

 

MySQL通过视图（或临时表）实现动态SQL（游标）。

因在实现中，需要通过DDL语句创建视图（或临时表）、删除视图（或临时表），故，只适合在一些一次性的脚本中使用，比如调试一些数据问题、做一些简单的数据初始化。

不适合使用在涉及业务操作的程序中。

 

>使用view实现

drop procedure if exists p_simulate_dynamic_cursor;

create procedure p_simulate_dynamic_cursor()
begin
    declare v_sql varchar(4000);
        declare v_field varchar(4000);
        declare v_result varchar(4000) default '';
        declare cur_temp cursor for select v.* from view_temp_20150701 v;
        declare continue handler for not found set v_field = null;

        set v_sql = 'create view view_temp_20150701 as select t.id from t_user t';
        
        set @v_sql = v_sql;
        prepare statement from @v_sql;
        execute statement;
        deallocate prepare statement;

        open cur_temp;
        fetch cur_temp into v_field;
        while (v_field is not null) do
                set v_result = concat(v_result, v_field, ',');
                fetch cur_temp into v_field;
        end while;
        close cur_temp;
        select v_result;

        drop view if exists view_temp_20150701;
end;

call p_simulate_dynamic_cursor();
        

 

>使用temporary table实现

drop procedure if exists p_simulate_dynamic_cursor_by_temp_table;

create procedure p_simulate_dynamic_cursor_by_temp_table()
begin
    declare v_sql varchar(4000);
        declare v_field varchar(4000);
        declare v_result varchar(4000) default '';
        declare cur_temp cursor for select t.* from t_temp_20150701 t;
        declare continue handler for not found set v_field = null;

        set v_sql = 'create temporary table t_temp_20150701 as select t.id from t_user t limit 0, 100';
        
        set @v_sql = v_sql;
        prepare statement from @v_sql;
        execute statement;
        deallocate prepare statement;

        open cur_temp;
        fetch cur_temp into v_field;
        while (v_field is not null) do
                set v_result = concat(v_result, v_field, ',');
                fetch cur_temp into v_field;
        end while;
        close cur_temp;
        select v_result;

        drop temporary table if exists t_temp_20150701;
end;

call p_simulate_dynamic_cursor_by_temp_table();