Question

我有一个名为my_db的数据库。 my_db中的每个表都有一列set_id，其值在2140到2180之间。我想遍历my_db中的所有表并删除行set_id大于2170。我该怎么做？

Answer 1

我认为，这不是对此的查询，但是您可以执行以下操作

SELECT CONCAT('delete from my_db.',table_name,' where set_id > 270') FROM information_schema.tables where table_schema='my_db';

其结果是您需要运行的所有查询。您可以复制并运行它。

Answer 2

我喜欢Marco的答案，因为它简短易懂，并且提供了一种不错的解决方法。这就是我使用“过程”，“同时循环”和“预准备语句”提出的。无需复制。

它检索并将其存储到一个临时表中，然后遍历每个表名并执行单独的DELETE语句。

DROP PROCEDURE IF EXISTS myPurge;

-- Will be used to signify the end of the procedure
DELIMITER ;;

-- Use a procedure
CREATE PROCEDURE myPurge()
BEGIN

    -- Retrieve tables from information_schema and
    -- Store them into a temporary table
    DROP TABLE IF EXISTS tempTables;
    CREATE TEMPORARY TABLE tempTables
        SELECT table_name FROM information_schema.tables WHERE table_schema = 'my_db';

    -- Initialise variables
    SET @i = 0;
    SELECT COUNT(*) FROM tempTables INTO @n;

    -- Loop from 0 to number of rows
    WHILE @i < @n DO

        -- Retrieve table from row @i
        -- SELECT * FROM tempTables LIMIT @i, 1 INTO @atable; -- doesn't seem to work on MySQL v5

        -- Prepare and execute a subsidiary query
        SELECT CONCAT("SELECT * FROM tempTables LIMIT ", @i, ",1 INTO @atable") INTO @preLimStmt;
        PREPARE limStmt FROM @preLimStmt;
        EXECUTE limStmt;

        -- Save statement into temporary variable
        -- HERE we prepare your PURGE
        SELECT CONCAT("DELETE FROM my_db.", @atable, " WHERE set_id > 2170") INTO @preStmt;

        -- Prepare and execute the purge statement
        PREPARE stmt FROM @preStmt;
        EXECUTE stmt;

        -- Increment @i
        SET @i = @i + 1;

    END WHILE;

END;;

-- Call the procedure
CALL myPurge();

-- cleanup
DEALLOCATE PREPARE limStmt;
DEALLOCATE PREPARE stmt;

-- Reset to default
DELIMITER ;

-- Remove the temporary table
DROP TABLE tempTables;

注意：我正在使用MySQL版本5.7.23。

如何从MySQL数据库的所有表中删除特定行？

2 个答案: