使用mysql alter命令可能导致数据丢失？

Question

虽然我不认为数据丢失是可能的，但我想仔细检查下列查询是否会导致数据丢失。我正在添加索引并增加varchar长度。

ALTER TABLE `phppos_sales` ADD `deleted` INT(1) NOT NULL DEFAULT '0'; 
ALTER TABLE `phppos_items` ADD INDEX ( `name`); 
ALTER TABLE `phppos_items` ADD INDEX ( `category`); 
ALTER TABLE `phppos_items` ADD INDEX ( `deleted`); 
ALTER TABLE `phppos_customers` ADD INDEX ( `deleted`); 
ALTER TABLE `phppos_employees` ADD INDEX ( `deleted`); 
ALTER TABLE `phppos_giftcards` ADD INDEX ( `deleted`); 
ALTER TABLE `phppos_item_kits` ADD INDEX ( `name`); 
ALTER TABLE `phppos_people` ADD INDEX ( `first_name`); 
ALTER TABLE `phppos_people` ADD INDEX ( `last_name`); 
ALTER TABLE `phppos_people` ADD INDEX ( `email`); 
ALTER TABLE `phppos_sales` ADD INDEX ( `deleted`); 
ALTER TABLE `phppos_suppliers` ADD INDEX ( `deleted`); 
ALTER TABLE `phppos_receivings` CHANGE `payment_type` `payment_type` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NULL DEFAULT NULL; 
ALTER TABLE `phppos_receivings_items` CHANGE `description` `description` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NULL DEFAULT NULL; 
ALTER TABLE `phppos_receivings_items` CHANGE `serialnumber` `serialnumber` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NULL DEFAULT NULL; 
ALTER TABLE `phppos_sales` CHANGE `payment_type` `payment_type` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NULL DEFAULT NULL; 
ALTER TABLE `phppos_sales_suspended` CHANGE `payment_type` `payment_type` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NULL DEFAULT NULL; 
ALTER TABLE `phppos_giftcards` CHANGE `giftcard_number` `giftcard_number` VARCHAR(255) CHARACTER SET utf8 COLLATE utf8_unicode_ci NOT NULL; 
ALTER TABLE `phppos_sales_items` CHANGE `description` `description` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NULL DEFAULT NULL; 
ALTER TABLE `phppos_sales_items` CHANGE `serialnumber` `serialnumber` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NULL DEFAULT NULL; 
ALTER TABLE `phppos_sales_suspended_items` CHANGE `description` `description` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NULL DEFAULT NULL; 
ALTER TABLE `phppos_sales_suspended_items` CHANGE `serialnumber` `serialnumber` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NULL DEFAULT NULL; 
ALTER TABLE `phppos_sales_suspended_payments` CHANGE `payment_type` `payment_type` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NOT NULL; 
ALTER TABLE `phppos_sales_payments` CHANGE `payment_type` `payment_type` VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_swedish_ci NOT NULL; 

Answer 1

无论如何，您应该比较操作前后的数据。

做mysqldump --extended-insert=FALSE ... > old.sql改变之前，和> new.sql改变之后，然后diff -u old.sql new.sql | less可以肯定。

需要使用extended-insert=FALSE零件将每个表格行放在单独的行上，以便更容易地使用diff。