MySQL 遍歷表

Question

我想從包含first_name列的每個表中輸出數據。 我將以下過程放在一起，但在我的循環中，mysql 從字面上解釋表名，而不是評估變量table_name 。 有什么解決辦法？

delimiter //

drop procedure if exists hunt //
create procedure hunt()
begin
    DECLARE done int default false;
    DECLARE table_name CHAR(255);

    DECLARE cur1 cursor for SELECT TABLE_NAME FROM INFORMATION_SCHEMA.COLUMNS 
        WHERE TABLE_SCHEMA = "wholesale_production" and COLUMN_NAME LIKE "%first%" ;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    open cur1;

    myloop: loop
        fetch cur1 into table_name;
        if done then
            leave myloop;
        end if;
        select * from `wholesale_production`.table_name where created_at >= '2012-10-01';
    end loop;

    close cur1;
end //

delimiter ;

call hunt();

Answer 1

試試這個：

delimiter //

drop procedure if exists hunt //
create procedure hunt()
begin
    DECLARE done BOOL default false;
    DECLARE tablename CHAR(255);

    DECLARE cur1 cursor for SELECT TABLE_NAME FROM INFORMATION_SCHEMA.COLUMNS 
        WHERE TABLE_SCHEMA = "wholesale_production" and COLUMN_NAME LIKE "%first%" ;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    open cur1;

    myloop: loop
        fetch cur1 into tablename;
        if done then
            leave myloop;
        end if;
        set @sql = CONCAT('select * from `wholesale_production`.', tablename, ' where created_at >= ''2012-10-01''');
        prepare stmt from @sql;
        execute stmt;
        drop prepare stmt;
    end loop;

    close cur1;
end //

delimiter ;

call hunt();

Answer 2

對上述內容進行一些編輯以迭代 ahtoug 所有表並選擇它們。

delimiter //
drop procedure if exists hunt //
create procedure hunt()
begin
    DECLARE done int default false;
    DECLARE table_name CHAR(255);

    DECLARE cur1 cursor for SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
                  WHERE table_schema ='mbu4u';
   DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    open cur1;
       myloop: loop
        fetch cur1 into table_name;
        if done then
            leave myloop;
        end if;
        set @sql = CONCAT('select * from `mbu4u`.',table_name);
        prepare stmt from @sql;
        execute stmt;
        drop prepare stmt;
    end loop;

    close cur1;
end //

delimiter //

Answer 3

table_name 是保留標記在“DECLARE table_name CHAR(255);”中使用另一個變量名

Answer 4

在 cur1 中，您正在使用 TABLE_NAME 嘗試使用表的真實名稱