mysql - 从 mysql 的校验和表中选择并仅返回校验和(而不是表)

Question

当我运行“mysql> CHECKSUM TABLE mytable;”时，我得到以下结果:

+------------------+------------+
| Table            | Checksum   |
+------------------+------------+
| mydb.mytable     | 1679935596 |
+------------------+------------+

如何在一条 mysql 语句中选择并仅返回上述结果中的校验和(而不是表)？ 像“SELECT Checksum FROM (CHECKSUM TABLE mytable);”之类的东西？？？试了好几次了，还是不行。

我想要的是:

+------------+
| Checksum   |
+------------+
| 1679935596 |
+------------+

Answer 1

您可以按列或列的总和来执行此操作。下面是在我的 table 上进行的测试。

SELECT sum(crc32(email)) as crc from users;
+-------------+
| crc         |
+-------------+
| 10679459550 |
+-------------+


select sum(crc32(concat(user_id,first_name,last_name,email,reportingManager))) as crc from users;
+------------+
| crc        |
+------------+
| 7196315383 |
+------------+

编辑

在传递数据库名称和表名称的存储过程中，下面将返回 crc。它会转到特殊的 INFORMATION_SCHEMA 数据库来为您检索列名称，并使用所有这些列和值来生成校验和。

存储过程:

drop procedure if exists getTableCRC32;
DELIMITER $$
create procedure getTableCRC32
(   dbname varchar(80),
    tableName varchar(80)
)
BEGIN
    set @sql1="select GROUP_CONCAT(`column_name` SEPARATOR ',') into @colNames";
    set @sql1=concat(@sql1," FROM `INFORMATION_SCHEMA`.`COLUMNS`");
    set @sql1=concat(@sql1," WHERE `TABLE_SCHEMA`='",dbName,"'");
    set @sql1=concat(@sql1," AND `TABLE_NAME`='",tableName,"'");
    -- select @sql1;
    PREPARE stmt1 FROM @sql1;
    EXECUTE stmt1;
    DEALLOCATE PREPARE stmt1;
    -- select @colNames;
    set @sql2=concat( 'select sum(crc32(concat(',  @colNames, '))) as crc from ',tableName);
    -- select @sql2;
    PREPARE stmt2 FROM @sql2;
    EXECUTE stmt2;
    DEALLOCATE PREPARE stmt2;
END
$$
DELIMITER ;

测试一下:

call getTableCRC32('so_gibberish','users');
+------------+
| crc        |
+------------+
| 7196315383 |
+------------+
call getTableCRC32('so_gibberish','fish');
+------------+
| crc        |
+------------+
| 3273020843 |
+------------+

Manual page for crc32